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TITLE PAGE

EFFECT OF CO-EXTRUDED FILM ON THE SHELF STABILITY OF

SLICED SALTED PORK MEAT PRODUCT

A THESIS PRESENTED TO THE DEPARTMENT OF FOOD SCIENCE

AND TECHNOLOGY IN PARTIAL FULFILLMENT OF THE

REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN

FOOD SCIENCE AND TECHNOLOGY

BY

OMELAGU, CHIZOBA AMBROSE

PG/MSc./06/42121

DECEMBER, 2012

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CERTIFICATION

OMELAGU, CHIZOBA AMBROSE, a postgraduate student in the Department of Food Science

and Technology, Faculty of Agriculture, University of Nigeria, Nsukka has satisfactorily

completed the requirements, for the award of the degree of Master of Science (M.Sc.) in Food

Science and Technology. The work embodied in this project report is original and has not been

submitted in part or full for any other diploma or degree of this or other university.

Supervisor Signature and Date

Prof. A.I. Ikeme

Head of Department Signature and Date

C.S. Bhandary

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DEDICATION

This dissertation is dedicated to my late mother Mrs. Mabel Ugoada Omelagu “Cedar”. She was

my pillar of strength, a mentor and a friend; I could have never had a better mother. I will forever

treasure your memories mum, till we meet again someday.

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ACKNOWLEDGMENT

First and foremost, I thank God for seeing me through this programme successfully. I

owe a debt of gratitude to my supervisor, Prof. A.I. Ikeme for providing me with the necessary

guidance and time, without which this work would not have been possible. My sincere gratitude

is to Prof. T.M. Okonkwo, Dr.G.I. Okafor, C.S. Bhandary, Prof.(Mrs.) N.J. Enwere (late), Dr.

(Mrs.) I. Nwaoha, Prof. (Mrs.) J.C. Ani, Prof. S.O.C. Ugwu, Mr. G.O. Odigbo(late), Dr.(Mrs.) I.

Asogwa and all of the staff of Department of Food Science and Technology, University of

Nigeria, Nsukka. Words cannot express my appreciation to Mrs. Akpama of University of

Calabar and Mr. Otogbo, O. O. of Cross Rivers State Agricultural Development Programme for

their contribution. I pay my great gratitude to staff and management of Chumaco Plastic

Industries, Onitsha, Anambra state for allowing me to use their plant line. I am grateful to all

laboratory staff of Food Science and Technology especially Mr. C. Diarua, Mr. C. Ezeugwu, Mr.

C. Nnanna and Mr. U. Bosah, also to Miss Oluchi (Animal Science), Miss Obioma and Mr.O.E.

Ikwuagwu (Biochemistry).

I am thankful to all my colleagues especially Saibolo, Henry, Grace and Frances who

always helped me to complete my work. I feel it incomplete if I do not extend my fervent thanks

and heartiest compliments to my father Mr. G.O. Omelagu and brothers- Nnagozie and Mac-

Donald for their constant encouragement, unflinching support and love. Also Bro. A. Abali, Bro.

A. Oruruo and Bro. A. Madubuko for their invaluable advice they gave me at inception of this

project. Special thanks go to members of Gate of Heaven Students‟ Bloc Rosary Crusade, St.

Peters Catholic Chaplaincy, University of Nigeria, Nsukka for their prayers.

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TABLE OF CONTENTS

Certification - - - - - - - - - - i

Dedication- - - - - - - - - - - ii

Acknowledgement- - - - - - - - - - iii

Table of Contents- - - - - - - - - - iv

List of Figures- - - - - - - - - - vi

List of Tables - - - - - - - - - - vii

Abstract - - - - - - - - - - - viii

CHAPTER ONE: INTRODUCTION- - - - - - - 1

1.1 Background Information - - - - - - - - 1

1.2 Problem Statement- - - - - - - - - 2

1.3 Objective of the Study- - - - - - - - - 4

1.4 Impact/Significance of the Study- - - - - - - 4

CHAPTER TWO: LITERATURE REVIEW - - - - - 5

2.1 Purpose of Packaging Processed Meat- - - - - - - 5

2.2 Factors Affecting the Shelf-Life of Meat and Meat Products- - - - 6

2.3 Packaging Materials for Meat Products- - - - - - 9

2.4 Co-Extrusion of Films - - - - - - - - - 10

2.5 Meat Products - - - - - - - - - - 16

2.6 Salted Meat- - - - - - - - - - 17

2.7 Analytical Frameworks - - - - - - - - 19

2.8 Prediction of Shelf Life - - - - - - - - 20

CHAPTER THREE: MATERIALS AND METHODS - - - - - 23

3.1 Sample/Material Procurement and Processing - - - - - 23

3.1. 1 Preparation of Samples/Raw Materials - - - - - - 23

3.2 Temperature and relative of storage room - - - - - - 25

3.3 Chemical Analysis of Sample- - - - - - - - 25

3.3.1 Moisture Content - - - - - - - - - 25

3.3.2 Crude protein - - - - - - - - - - 25

3.3.3 Fat Content - - - - - - - - - - 26

3.3.4 Water Activity - - - - - - - - - - 26

3.3.5 pH Determination - - - - - - - - - 26

3.3.6 Salt (sodium chloride) content- - - - - - - 27

3.3.7 Protein solubility - - - - - - - - - 27

3.3.8 Thiobarbituric Acid Reactive Substances (TBARS) - - - - 27

3.3.9 Free Fatty Acid - - - - - - - - - 28

3.3.10 Vitamin Analysis - - - - - - - - - 28

3.3.10.3 Vitamin A - - - - - - - - - - 28

3.3.10.2 Vitamin C (Ascorbic acid) - - - - - - - 29

3.3.10.1 Vitamin E - - - - - - - - - - 30

3.4 Microbial Analysis - - - - - - - - - 30

3.4.1 Total Viable Count - - - - - - - - - 30

3.4.2 Mould Count Determination - - - - - - - 31

3.5 Sensory Evaluation of Samples - - - - - - - 31

3.6 Statistical Analysis - - - - - - - - - 32

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3.7 Microstructure Characterisation - - - - - - - 32

3.8 Coefficient of Friction - - - - - - - - - 32

CHAPTER FOUR: RESULTS AND DISCUSSION - - - - - 33

4.1 Storage Temperature and Relative Humidity - - - - - - 33

4.2 Mechanical Properties - - - - - - - - - 34

4.3 Results on Chemical Analysis of Samples - - - - - - 36

4.4 Microbial Analysis Results - - - - - - - - 54

4.5 Organoleptic Characteristics - - - - - - - - 57

CHAPTER FIVE: CONCLUSION AND RECOMMENDATIONS - - - 60

5.1 Conclusion - - - - - - - - - - 60

5.2 Recommendations - - - - - - - - - 60

REFERENCES - - - - - - - - - - 61

APPENDICES - - - - - - - - - - 68

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LIST OF FIGURES

Figure1: Flow chart of processing of unam inung meat product - - - - 24

Figure2: Micrograph of the experimental plastic film - - - - - 35

Figure3: Changes in moisture content (%) of unam inung stored with different

packaging materials for six months at ambient temperature - - - 39

Figure 4: Changes in crude protein content (%) of unam inung stored with

different packaging materials for six months at ambient temperature- - 40

Figure 5: Changes in crude fat content (%) of unam inung stored with different

packaging materials for six months at ambient temperature- - - 42

Figure 6: Changes in water activity of unam inung stored with different packaging

materials for six months at ambient temperature- - - - - 44

Figure 7: Changes in pH of unam inung stored with different packaging materials

for six months at ambient temperature- - - - - - 45

Figure 8: Changes in NaCl content (%) of unam inung stored with different

packaging materials for six months at ambient temperature- - - 46

Figure 9: Changes in protein solubility (%) of unam inung stored with different

packaging materials for six months at ambient temperature- - - 48

Figure 10: Changes in TBARS of unam inung stored with different packaging

materials for six months at ambient temperature- - - - 50

Figure11: Changes in FFA of unam inung stored with different packaging materials

for six months at ambient temperature- - - - - - 51

Figure 12: Changes in vitamin A of unam inung stored with different packaging

materials for six months at ambient temperature- - - - 52

Figure 13: Changes in vitamin C of unam inung stored with different packaging

materials for six months at ambient temperature- - - - 53

Figure 14: Changes in vitamin E content of unam inung stored with different packaging

materials for six months at ambient temperature- - - - - 54

Figure 15: Changes in total viable count of unam inung stored with different

packaging materials for six months at ambient temperature- - - 56

Figure 16: Changes in mould count of unam inung stored with different

packaging materials for six months at ambient temperature - - - 57

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LIST OF TABLES

Table 1: Different category of meat product - - - - - - 7

Table2: Materials, properties and applications for two, three and five layer structures- 12

Table 3: Room mean monthly temperature and relative humidity readings- - - 34

Table 4: Coefficient of friction - - - - - - - - 34

Table 5: Correlation matrix of the parameters studied in unam inung- - - 36

Table 6: Quality characteristic of freshly prepared unam inung - - - - 38

Table 7: Sensory characteristics of unam inung over a 6 months storage period with

different packaging materials - - - - - - - 59

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ABSTRACT

The study evaluated the efficiency of co-extruded polypropylene (PP) and low density polyethylene

(LDPE) in extending the shelf-stability of unam inung traditional meat product during storage under

ambient conditions. Fresh pork was processed, in traditional way, into unam inung meat product and

stored for 6 months, under ambient room conditions as unpackaged, clay pot packaged (traditional

method), and those packaged in polypropylene (PP), low density polyethylene (LDPE) and co-extruded

polypropylene/low density polyethylene (PP/LDPE). Samples were withdrawn at intervals of one month

for evaluation of quality changes. Results show that the storage room temperature (25.95-27.91oC) and

relative humidity (68.25-77.42%) are suggestive of typical diurnal conditions during the beginning of

rainy season in South Eastern States of Nigeria. Relative humidity (RH) which was 69.55% at the

beginning of storage reduced to 68.29% in the 2nd

month of storage and subsequently increased thereafter

to 77.42% in the 5th month of storage. Due to increasing RH from the second month of storage, all

products increased in moisture content, consequently leading to increases in water activity and reduction

in crude protein, fat and salt content due to dilution effect resulting from mass action. These changes were

greater in the unpackaged and clay pot packaged samples due to greater access to air and moisture but

least in the PP/LDPE coextruded film due to greater restriction to air and moisture transmission. Owing to

increasing moisture and water activity from the second month of storage, protein hydrolysis became the

dominant protein deteriorative reaction, leading to increases in protein solubility and pH, particularly in

the unpackaged but significantly least in the PP/LDPE co-extruded plastic film. Thiobarbituric acid

reactive substances (TBARS) and free fatty acids (FFA) results suggest that both oxidative and hydrolytic

rancidity were occurring in the samples but the extent was very low and did not lead to detectable

rancidity in any sample. The reactions of the antioxidant vitamins (A,C and E) must have been effective

in preventing detectable rancidity, as they all have significant (p<0.05) correlations {r(Vitamin

C/TBARS) = -0.743, r(Vitamin C/FFA) = -0.586, r(Vitamin A/TBARS) = -0.882, r(Vitamin A/FFA) = -

0.794, r(Vitamin E/TBARS) = -0.753 and r(Vitamin E/FFA) = -0.831}. All the vitamins continued to

reduce during storage. Total viable count and mould count significantly (p<0.05) increased in the

unpackaged samples throughout storage period presumably due to greater access to moisture and air.

These counts reduced in the plastic film packages, particularly PP/LDPE package, probably due to

restricted/lower availability of oxygen and moisture. Although all the sensory attributes slightly reduced

during storage, the reductions did not lead to significant loss of acceptability. All deteriorative

reactions/changes were more adverse in the unpackaged samples and clay pot packaged samples

compared co-extruded PP/LDPE packaged samples. Thus, unam inung packaged with co-extruded

PP/LDPE plastic film is acceptable up to 6 months of storage at ambient room conditions without much

loss in quality. On the other hand, the unpackaged and clay pot packaged samples showed much

instability and spoilage that they were discarded after about 3 and 5 months respectively.

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CHAPTER ONE

INTRODUCTION

1.1 Background Information

Meat products have broad categories that require different types of packaging. Selection

of packaging materials will depend on product factors such as colour stability, storage conditions,

microbial condition, degree of processing preservative and attractiveness of the packs (Hotchkiss,

1994; Konieczny and Bilska, 2006). The packaging film must be a barrier against environmental

influence in order to protect and preserve the product. Hence, the barrier requirement depends on

the type of meat. Meats which are stored at room temperature for months (example, commercially

sterile meats) must be protected from oxygen ingress and loss of water. Packaging must also

provide a barrier against biological, chemical and physical agents that would detract from quality

or safety (Ramsbottom, 1971; Proffit, 1991).

Packaging materials can be classified into metal, paperboard laminates, plastic and glass.

Metal and glass are ideal materials for packaging meat; both have absolute barrier against

molecular diffusion and provide good protection of the packed product according to the reliable

hermetic seal and firmness of the container, but they require high packaging costs and are not

flexible. Paperboard laminates and plastic containers reduce packaging cost considerably and are

extensively flexible. Therefore, they are most frequently used in packaging systems, but do not

have perfect barrier against matter and energy (Hotchkiss, 1994).

Plastics used now are petroleum derivatives, mainly thermoplastic resins. The four most

economic plastics are polyethylene (PE), polyvinyl chloride (PVC), polypropylene (PP) and

polystyrene (PS) (Dean, 1996). Plasticizers, colourants or anti-fog compounds may be added in

their fabrication (USDA-FSIS, 2002). Thermoplastic films have gained a dominating position in

the field of packaging over several decades, but in the last few years there has been a growing

interest in co-extruded materials. The co-extrusion process enables the properties of different

polymer resins to be combined in one film, since the requirements of a package cannot always be

met by a single film. Co-extrusion of containers have the advantage of glass (Clarity, retortability

and barrier properties) coupled with the advantages of safety (impact resistance), low weight, ease

of shaping and printing. These have led to the opening of new markets in both food and medical

disciplines (Fox, 1990; Mc Cormick and Tas, 2005). With advances in co-extrusion technologies,

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plastics can now be engineered to provide a wide range of properties to satisfy the many levels of

protection needed by foods and beverages (Yam et al., 1999).

The excellent gas, odour and water vapour properties of barrier materials have resulted in

co-extruded products with a widespread market acceptance in a variety of end uses. These new

developments in high barrier plastics are in line with the main objectives of packaging

developments in today‟s demanding world (Groof, 1993; SPI, 2005). The major increase in the

use of multi-layer co-extruded films for packaging applications in the last few years is in the high

barrier film area, particularly for products with high fat content (Fox, 1990). Consequently, this

technique can be used to package some of our traditional meats like unam inung. Unam inung is a

ready-to-eat pork product that is very popular in the South-South states of Nigeria. The product is

traditionally prepared by heavily salting sliced pork which is then sun dried and packed in dry

clay pot. It is most commonly served with cassava chips or boiled yam and plantain. The

traditional production techniques especially in packaging have not been improved to cope with

modern scientific requirements and with increasing demand (Hui, 2007).

1.2 Problem Statement

The demand for protein of animal origin in a developing country like Nigeria far outstrips

the supply. An average Nigerian, for instance, consumes only about 10g per day of the minimum

daily intake of 35g recommended by Food and Agricultural Organisation (FAO, 1992). The fast

growth rate and the high prolific nature of pigs can close the gap of protein shortage. If pork

products are made readily available at affordable cost, animal protein shortage will be alleviated

(Ani and Okorie, 2004; Oboh et al., 2004).

Meat, traditionally preserved by drying, is made available sometimes in packaged linen

bags, baskets or pottery to facilitate storage and transport and to provide some kind of protection

against dirt, insects, etc. With teeming population of consumers, however, this traditional system

now becomes outmoded because more time is needed between slaughtering and ultimate

consumption. Meat frequently has to be stored, transported, prepared and distributed through a

retailer or butcher of which is considerably time-consuming. In order to safeguard fresh meat

during this extended time, certain methods of preservation have to be applied. Refrigeration is a

type of solution, but this is expensive and therefore frequently not available in Nigeria. To extend

the shelf-life of meat and meat products, proper packaging has an important part to play especially

due to absence of refrigeration.

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Over the years, a number of traditional Nigerian/African meat products have gained

universal acceptability. These products included barbecued meats such as 'tsire' (suya) and

balangu; sun-dried or dehydrated meat products such as kilishi, and smoke-dried meat products

like banda, kundi and unam inung. These traditional meat products are popular, convenient and

leisure food items whose consumption has become invariant with socioeconomic class.

However, poor packaging or absence of same restricts their usage and stability. They are

still packaged with newspaper, clay pot and sometimes inappropriate single film polyethylene

which are possible source of contamination (Uzeh et al., 2006). Consequently, oxidation may

occur extremely rapidly in these products after processing, and the characteristic “warmed-over

flavour” may occur. This flavour development makes lengthy storage of the meat practical

impossibility. Oxygen cannot be prevented from reaching the meat since the films used are not

oxygen impermeable. This shortfall constrains the marketing and distribution of large amounts of

meat products to distant consumption centres. Some of the causes of these poor packaging are

finance and technology.

There is need to seek ways to extending the shelf stability of these meat products through

packaging to augment the impact of processing for longer shelf-life. Any means of augmenting

the performance of these indigenous meat products through packaging may offer some solutions

to this age long problem. Since cost and technology are major constraints to improved packaging

of these meat products, attempt was proposed in this work to exploit available technology and

cheaper raw material. Co-extrusion of packaging films such as polyethylene and polypropylene

offers likely advantage; it will guarantee low cost while incorporating the barrier properties of

polypropylene and polyethylene.

The cost of extrusion of suitable single films is high considering the low capitalization

status of the producers of these meat products. Plastic films like polypropylene, polyamide,

polyvinylchloride and polyvinylidenechloride have good barrier properties against matter and

energy (Yam et al., 1999). Few can be extruded locally but are not popular because their resins

are expensive. Though the resins for these films are abundant locally as by-products of the

petrochemical industry, very few plastic extruders have the technology to exploit them. They are

hence scarce and not used commonly.

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1.3 Objective of the Study

The main objective of this research was to verify the effect of packaging films on the

quality of the unam inung meat. The specific objectives were to:

a) Source and co-extrude Polyethylene and Polypropylene resins

b) Obtain each of the film separately

c) Package unam inung in these films

d) Assess performance of the films over six months‟ storage

1.4 Impact/Significance of the Study

There is recently, rapid development in meat based fast food industry with preference for

processed products, and the scope for production of traditional meat products has increased

immensely, creating a need for developing technologies for manufacturing indigenous products

on large commercial scale to meet the demands of growing population (Bhat et al., 2011; FAO,

2007).

The successful completion of this study will improve regional and local availability of

packaging materials for unam inung and other local meat products. Small and medium scale

enterprises can access better quality packaging film that will make them to compete equitably in

international markets. The improved processing and delivery of these products to consumers have

the potential to transform the wasteful Nigerian livestock and meat industry into dynamic and

active enterprise.

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CHAPTER TWO

LITERATURE REVIEW

2.1 Purpose of Packaging Processed Meat

The primary purpose of a package for meat and meat products are to protect the product

from contamination by dirt, micro-organisms, moulds, yeasts, parasites, toxic substances or those

influences affecting smell and taste or causing loss of moisture; and to present the product to the

consumer in the most attractive manners and against physical damage during the distribution

process, including storage and transport (Ramsbottom, 1971; FAO, 1990; Hotchkiss, 1994;

Konieczny and Bilska, 2006). Packaging should help to prevent spoilage, weight losses and

enhance customer acceptability (Hotchkiss, 1994; CTA, 2006). Frequently, full advantage of

packaging can only be achieved in combination with preservation methods such as drying (FAO,

1990). The most fundamental function of packaging is to contain and unitize the product into

sizes and cuts required for the market. Packaging must allow the meat product to be produced

and distributed efficiently and economically. Costly and inefficient packages will not be

successful. Packaging is a significant factor in the low cost of food in most of the developed

world (Hotchkiss, 1994).

Consequently, processed meat products include canned and dried meats, both of which

are stored at ambient temperatures. Dried meats may be stored at room temperature for periods

of months to years but most do not retain quality. The mechanisms of deterioration are loss of

water, oxidation of lipids and pigments, or, in some cases, microbiological deterioration.

Oxidation results in the development of rancid off-flavours and/or changes in colour and

appearance. Packaging reduces oxidation by reducing the amount of oxygen available to react

with the pigment and by reducing the transmission of ultra-violet light. While barrier properties

are used to control both microbiological and oxidative forms of deterioration, the strength of

polymer films used for processed meats must have excellent heat-sealing properties.

In developing packaging, the technologist is also concerned with the product name,

ingredient statement, nutritional analysis, cooking or reconstitution instructions, product size,

and net weight (Hand, 1994). The pack must be economical and therefore contribute to overall

profitability, it must provide protection against climatic, biological, physical and chemical

hazards; it must provide an acceptable presentation which will contribute to or enhance product

confidence whilst at the same time maintaining adequate identification and information; and

must contribute in terms of convenience and compliance. Each of these aspects has to be

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considered against the total shelf-life of the product. The external image of the pack must not

only compliment product confidence, provide clear and concise product identification, adequate

information related to the contents (including legal requirements), the route of opening, storage

conditions, batch number, expiry date, manufacturer‟s name and address, and product licence

number (Hotchkiss,1994). Product is tested in a range of possible packs, usually over a range of

conditions from say -20oC to 45

oC, together with some cycling conditions covering a

temperature-humidity range. Feasibility tests usually extend over 1-12 month test periods with 3-

6 months normally, being the minimum period of test before a decision to proceed with a certain

pack is taken (Dean, 1996).

2.2 Factors Affecting the Shelf-Life of Meat and Meat Products

There are endogenous factors, such as:

pH-value or the degree of acidity of the product

aw value or the amount of moisture available in the product

And exogenous factors, such as:

oxygen (from the air);

micro-organisms;

temperature;

light;

evaporation.

EFFECT OF pH- AND Aw-VALUE

The shelf-life of meat and meat products will be longer the lower the pH-value and/or

aw-value. Both factors have a decisive influence on the growth of micro-organisms in food.

However, there are limits for most meat products regarding decreased pH-value and aw-value,

particularly for organoleptic reasons. Except for some special products, consumers do not want

meat products to be excessively acidic or dry. Shelf-stable products have a pH-value of or below

5.2 and an aw-value of or below 0.95, or only a pH-value below 5.0, or only an aw-value below

0.91. No refrigeration is required in these cases, the products remaining stable under ambient

temperatures. The most common products in this group are the various kinds of dried meat

(FAO, 1990; Konieczny and Bilska, 2006).

The essential feature of this method of preservation is that the water activity of the meat

is reduced to a level below that at which microorganisms can grow. The range of physical,

biochemical, chemical and microbiological changes occurring during storage of food may be

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reduced considerably by decreasing water content or causing the transition of free water to bound

water, unavailable for the above mentioned changes deteriorating the quality of food. The most

frequently applied methods include drying, smoking, freezing and adding substances exhibiting

osmoactive properties, especially sugar or table salt. The practical role of this quality parameter

is important for each food product is growing along the development of the methods of food

sales, with the expanding network of self-service shops and supermarkets, and in any other place

where commercial portioning and packaging of products takes place (Konieczny and Bilska,

2006).

By drying, foods are stabilized against attack by micro organisms, and enzymes and

biochemical degradation is limited. This reduction is accompanied by a corresponding reduction

in the weight and storage space (Paine and Paine, 1992). To ensure a reasonably short drying

cycle, slices of meat should be cut to thickness of about 15mm (Snowman, 1997).

However, this does not mean that the products remain stable for an undetermined period.

Their shelf-life will be limited by chemical or physical deterioration. In this situation the product

quality will benefit from the application of suitable packaging materials, which reduce the

physical and chemical influences on the product or protect the product completely (FAO,1990).

Finally, muscle with higher pH is more susceptible to microbial problems and conversely,

oxidation of meat pigment is favoured by lower pH (Estrada-munoz et al.,1998). Table 1 shows

the different category of meat product.

Table 1: Different category of meat product

CATEGORY CRITERIA STORAGE TEMPERATURE EXAMPLE

a) Easily perishable aw> 0.95 and pH>5.2 + 5°C fresh meat

b) Perishable aw 0.91–0.95 and pH< 5.2 + 10°C Carne-de-sol

c) Shelf stable aw < 0.91or pH < 5.2 No refrigeration required Charque

Source: (FAO, 1985; Konieczny and Bilska, 2006).

OXYGEN

The oxygen content in the air is about 20 percent. If oxygen affects meat and meat

products during prolonged storage periods, it will change the red colour into grey or green and

cause oxidation and rancidity of fats with undesirable off-flavours (FAO, 1990).The plastic

materials used for food packaging differ in their permeability to oxygen. The lower the oxygen

17

permeability of the packaging material, the more efficient will be the protection of product

quality. Thiobarbituric acid-reactive substances (TBARS) and volatiles data indicated that

preventing oxygen exposure after cooking pork meat was very important in packaging due to

lipid oxidations and flavour of the meat (Ahn et al., 1998).

The products of lipid oxidation are responsible for unacceptable off-flavours and off-

odours in processed meats and limit the shelf-life of such meats (Kingston et al., 1998). Lipid

oxidation may be controlled by packaging with materials with high oxygen barrier properties

(Langourieux and Escher, 1998). The reactive oxygen species in foods lowers the overall

nutritional, chemical, and physical qualities of foods during storage and marketing. They

produce undesirable volatile compounds and carcinogens, destroy essential nutrients, and change

the functionalities of proteins, lipids, and carbohydrates (Choe and Min, 2005). Vitamins E, C,

and A have been found out to be important in protection against oxygen oxidation (Marks, 1993;

Choe and Min, 2005).

TEMPERATURE

Extremes of temperature (cold and hot) or cycling temperature can cause deterioration to

product and/or pack. Although higher temperatures generally represent an acceleration effect

occasions can be found where deterioration increases at lower temperatures (certain plastic will

become more brittle and crack). A high temperature coupled with a high R.H. will produce a

shower effect if the temperature is lowered sufficiently to reach dew point. Contamination from

liquid moisture can then encourage mould and bacterial growth (Dean, 1996).

LIGHT

The prolonged exposure of meat and meat products to daylight or artificial light

accelerates oxidation and rancidity because light provides the energy for these processes.

Transparent packaging films give no protection against light influences. Therefore, for products

under strong light exposure, coloured or opaque films should be preferred. Films laminated with

aluminium foil are absolutely impermeable to light. Products in transparent packaging film are

sufficiently protected when kept in the dark or under moderate illumination. Lipid oxidation may

be controlled in packaging with film protected against light (Langourieux and Escher, 1998).

Colour may reduce penetration or filter out selected wavelengths. This restricts light rays

entering the pack. Ultra-violate ray is a potential source of photochemical changes in a pack

(Dean, 1996).

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EVAPORATION

Fresh foods with relatively high moisture content such as meat will have considerable

losses of weight and quality by evaporation during storage if they are not packed. The packaging

material must therefore be sufficiently vapour-proof. Most plastic films used for food packaging

comply with this requirement. Organoleptic characteristics such as texture, juiciness, and

tenderness may be adversely affected by dehydration if the package is not moisture-vapour proof

(Ramsbottom, 1971).

SECONDARY CONTAMINATION

During slaughtering, carcass dressing, meat cutting and/or processing, the contamination

of meat to some extent cannot be avoided. The further growth of micro-organisms in meat and

meat products may not be stopped through packaging alone. Secondary contamination of these

foods, for example by contact with dust, dirty surfaces and hands, can definitely be prevented

through proper packaging, especially with plastic films which are absolutely impervious to

agents causing secondary contamination (FAO,1990).

Organoleptic characteristic such as flavour and odour loss or gain originating either from

the environment or within the product are influenced by the characteristics of the package.

Undesirable odours and flavours may be absorbed from outside sources if the package is

inadequate in barrier characteristics (Ramsbottom, 1971).

2.3 Packaging Materials for Meat Products

TRADITIONAL FOOD PACKAGING

Traditional food packaging refers to the packaging of traditional food in traditional

materials. In traditional food packaging set up, basic agricultural commodities are wrapped in

leaves and sheaths or kept in baskets, earthen ware pots, calabashes, gourds, drums etc. These

materials serve as containers for transport or as units of sale for their contents. Most of the

traditional packaging materials do not have the mechanical strength to protect their content;

hence they are not suitable for long distance transport or long term storage (N‟Diaye, 1986). It

involves a lot of energy and time input and it may involve carrying out of routine check on the

food packaging but this is not the case in modern day food packaging, where no such routine

checks are required once the food is packed.

19

SUITABLE MATERIALS FOR PACKAGING MEAT AND MEAT PRODUCTS

Packaging films for meat product can be subdivided into cellulose films, plastic films

and aluminium foil. They can either be used as monofilms or as two or more different films

laminated together. These materials differ in:

• Oxygen permeability;

• Water vapour barrier;

• Resistance to hot and cold temperatures; and

• Mechanical strength.

All thermoplastic materials are heat sealable, resulting in hermetically sealed plastic

pouches and bags (FAO, 1990). Of all the thermoplastics, polyethylene bags are commonly used

as packaging materials due to their low cost and convenience. The usage of PE bags may result

in reduced shelf-life of meat products because of increased fat oxidation and moisture absorption

rate in comparison to products in other resins which are more costly (Almeida-Dominguez et al.,

1992). A high oxygen barrier is important in the application of films for packaging meat and

meat products. Films made of polyethylene have relatively high oxygen permeability, whereas

polyvinylidenchloride (PVDC), polyester (PETP), polyamide (PA) cellulose film (ZG) and

polypropylene (PP) are less permeable to oxygen (Ramsbottom, 1971). The latter materials are

therefore better suited for packaging meat and meat products. However, the materials of the first

group are frequently used as laminates with materials of the second group in order to achieve

special effects regarding mechanical strength, heat sealing properties or making the package

practically impermeable to both oxygen and water vapour. Recently Odigbo (2007) reported that

use of vacuum packaged polypropylene kilishi indicated good keeping quality during storage

period of 40 weeks. Desirable properties may be combined to give a satisfactory composite. This

can be obtainable by co-extruding plastic polymers to form a single material (Taylor, 1985).

2.4 Co-Extrusion of Films

Desirable features used for food and health-care packaging are transparency, thermal

stability, physical strength, formability, sealability, biological barrier, radiation resistance, and

disposability. Often one cannot find all the desired properties in a single material, but two or

more plastics can be combined into a composite packaging material (Rabinow and Roseman,

2000). Co-extrusion is a process in which two or more layers of extrudable polymers brought

into contact while still in the amorphous and semimolten stage by the use of two or more

extruders and compound dies (Ramsbottom, 1971; Fox, 1990; Proffit, 1991; Turtle, 1993; Rosato

20

and Rosato, 2000; SPI, 2005). Two or more polymer melts can be co-extruded from film dies,

fed by the appropriate number of extruders. Many of the properties of such systems are additive;

for example, the gas permeability can be calculated by adding the resistances in series. In other

cases, synergism is encountered as when alternating different resins (Corish, 1992). This is

generally carried out by feeding separate polymer fluids, in most cases melt streams, from

different pumps to a die feed block. The fluids are generally combined in the die and emerge in a

combined form as a continuous extrudate. This is done for the purpose of improving properties,

particularly the degree of impermeability and the barrier restrains of the film (Whelan, 1994).

Multi- layered barrier films based on co-extrusion, achieve an optimal performance in long shelf-

life packaging in the most cost effective way (Groof, 1993).

Properties and applications

Co-extruded film products are most widely used in the packaging industry where there is

large diversity of requirements. There are often demands for high barriers characteristics against

for example, oxygen, carbon dioxide or water vapour in areas such as the cosmetic,

pharmaceutical, chemical and food industries. There may equally be demands for good

mechanical properties such as tensile strength, impact resistance or stiffness while other

applications may require excellent optical properties such as clarity, high gloss or low haze (Mc

Cormick and Tas, 2005). Other properties that might be specified could be resistance to oil and

solvents, antistatic properties, weather resistance and light stability. Similarly, requirements such

as heat stability, ease of printing or sterilisability may be needed. The possibilities and

combinations are almost infinite (Fox, 1990). No one thermoplastic has a variable combination

of such properties, hence the unique position of co-extruded materials (Rabinow and Roseman,

2000).

With the capability, for example, the fabricator can put together, polymers to add

functionality or improve the cost performance ratio of the final product of co-extrusion. Below

are some examples as outlined by Society of Plastics Industry (SPI) 2005:

High-gloss expensive layer over tough non-glossy less expensive substrate

Thin weatherable (usually expensive) layer over a tough non-weatherable substrate

Low gloss (may be expensive) layer over a tough substrate

A thin expensive decorative layer such as a marble or wood grain over a less expensive,

but tough substrate.

A vapour barrier extruded over a substrate

21

A chemically resistive material extruded over a less resistive substrate

A soft tough material over a cost-effective, tough substrate

Correctly colour matched cap over a non-coloured less expensive substrate

Ground up recycled parts may be re-extruded and utilized in a core or substrate layer of a co-

extruded sheet if the overall sheet physical properties can meet the toughness specifications for

the final product. In fact, the sheet extrusion/thermoforming industry has long ago demonstrated

the benefits of recyclability. The properties and applications of coextruded materials are shown

in Table 2.

Table2: Materials, properties and applications for two, three and five layer structures

Material combination Special properties Applications

Two layer structures

LDPE/LDPE High puncture resistance,

two colours

Milk pouches, carrier bags,

medical packaging

LDPE/LDPE recycle High resistance at low

thickness

Carrier bags

LDPE/HDPE High strength Waste bags, packaging for

pastries, rock salt, peat,

fertilisers

LDPE/LDPE foam Different colour weight Boutique bags

LDPE/LLDPE

LLDPE/LLDPE Excellent transparency,

good adhesion

Stretch wrap film for pallet

packaging

LLDPE/PP

LLDPE/HDPE Good strength at low

thickness

Carrier bags

LDPE/EVA

Weldable, sterilisable, good

strength

Blister packs, sterilisable packs,

protective films for glass

LDPE/Ionomer Tough at low temperature,

transparent

Packaging for dairy products,

frozen foods, medical goods

HDPE/EVA Weldable, sterilisable, high

strength

Linings for carton boxes, blood

plasma bags, bakery packaging

22

PP/EVA Sliced cheese packs

EVA/ionomer Weldable, oil resistant Packaging for bakery goods

and coconuts

PA/PA Salted meat packs

PA/ionomer Tough at low temperature,

good barrier

Packaging for deep frozen

foods, meat, fish, sausages,

ham, cheese

PS/SB Thermoformable, good

printability

Disposable cups, picnic ware,

packaging for dairy products

and ice

PC/ionomer Bag-in-box, medical envelopes

Three layer structures

LDPE/LDPE/LDPE Different colours, nacre

effect

Boutique bags

LDPE/LDPErecycle/LDPE Weldable Carrier bags, waste bags

LDPE/LDPE/PP Stretch wrap film for pallet

packaging

LDPE/HDPE/LDPE High resistance at low

thickness

Carrier bags

LDPE/HDPErecycle/LDPE Weldable, high strength,

stiff

Heavy duty dates, waste bags,

packaging for cereals and

pastries

LDPE/PP/LDPE Packaging for chips and bread

LDPE/HDPErecycle/HDPE Weldable, high strength,

stiff

Heavy duty bags, waste bags

LDPE/HDPE/LLDPE Weldable, high strength Carrier bags, milk powder

packs

LDPE/HDPErecycle/LLDPE High strength at low

thickness

Carrier bags

LDPE/LLDPE/LDPE High strength, transparent Industrial stretch film

LDPE/LLDPE/LLDPE High puncture resistance,

good adhesion

Heavy duty bags

23

LLDPE/LDPErecycle/LLDPE Weldable, good strength Refuse sacks

LLDPE/HDPE/LLDPE High resistance at low

thickness

Carrier Bags

LLDPE/PP/LLDPE High resistance at low

thickness

Carrier bags, industrial bags

HDPE/LDPE/HDPE Packaging for backed

confectionary products

LDPE/foamed LDPE/LDPE Low weight, soft feel,

insulant

Exclusive carrier bags, delicate

packaging

LDPE/LDPE/EVA Good barrier, UV, resistant,

multicoloured

Packaging for sweets, plants,

bakery products

LDPE/HDPE/EVA Slip and anti-slip properties

in/out layers

Industrial bags

LDPE/EVA/PP No sticking during shrink

wrapping

Shrink wrapping, packaging for

pastries and bakery goods

LDPE/EVA/K RESIN Thermoadhesive protective

films for glass

LDPE/tie/PA Good barrier properties Packaging for meat, ham,

cheese, fish, milk, pre-cooked

meals

LDPE/ionomer/PA Packaging for smoked fish and

dedicatessen goods

LDPE/ionomer/PC Transparent, sterilisable,

opaque to UV light

Packaging for medical products

PP/ionomer/PC

PP/LDPE/EVA Packaging for baked

confectionery goods

PP/tie/PVDC Thermoformable, good

barrier properties

Containers for pastuerisation

and sterilization of foodstuffs

PP/tie/EVOH

Ionomer/tie/PA Low temperature and high

seal strengths

Seal packs, packaging for oil

and fatty products

EVA/PP/EVA Weldable, sterilisable Packaging for dehydrate

vegetables

24

PS/SB white/PSrecycle Rigid, high surface gloss Containers for milk and milk

products

PS/recycle/HIPS

PA/ionomer/PC Transparent, sterilisable,

UV resistant

Bag-in-box packaging, medical

envelopes

Five layer structures

LDPE/tie/PA/tie/LDPE

LDPE/tie/PA/tie/PP Good barrier properties,

weldable, transparent

Packaging of meat, cheese,

sausages, ham, ready-cooked

meals shrink wrapping.

LDPE/tie/PA/tie/ionomers

LDPE/tie?PA/tie/EVA

LDPE/tie/EVOH/tie/LDPE Good barrier properties,

transparent

Packaging of foodstuffs

requiring high barrier properties

LDPE/tie/EVOH/tie/PP

LDPE/tie/EVOH/tie/ionomers Excellent oxygen and gas

barrier

Bag-in-box wine packs, bags

for fish meals

Source: (Fox,1990).

LDPE/tie/EVOH/tie/EVA

PP/tie/PVDC/tie/PP Good barrier giving long

shell-life

Containers for food packaging

EVA/tie/PA/tie/PAcopol Excellent barrier properties

Packaging of meat, pre-cooked

meals, milk powder

EVA/tie/EVOH/tie/PAcopol Packaging of medical items

PC/tie/EVOH/tie/PP High strength, excellent

barrier

Blow moulded containers for

food and medical items

25

Advantages of Co-extrusion

The main advantages of co-extruded films over conventionally produced laminates are

lower cost, a lower tendency towards delaminating and a greater flexibility in obtaining a wide

range of properties and finally, it avoids the high capital of adhesive laminating lines (Corish

1992; Turtle, 1993; Dean, 1996).

It is capable of producing excellent melt quality, uniformity and clarity (Reuter, 1993,

Davison, 1993). The lay-up can include recycled material or low cost material that will reinforce

more expensive material in strength and tear resistance (Davison, 1993, Rosato and Rosato,

2000; SPI 2005). Co-extrusion reduces plastic cost of colouring and demonstrate the use of silk-

screen printing in a variety of colours for plastic products especially polyolefin (Davison, 1993).

In printing the co-extruded material, the eventual side wall decoration contributes mainly to the

ultra violet barrier. Specific properties can be imparted to a film by co-extruding optimum

quantities of polymers (e.g. strength with transparency, high stiffness with high gloss, good

welds ability with sterilisability, excellent oxygen and gas barrier) (Fox, 1990; Briston, 1992).

Special visual and mechanical effects can be produced (example, see-through line, one side

cling, differently slips).

Cost savings in processing since co-extrusion is one-step process and can eliminate several

processing stages (e.g. in coatings and lamination). Expensive barrier properties can be used in a

thin layer [e.g., polyvinylidene chloride (PVDC), and ethylvinyl alcohol (EVOH)]. Overall film

thickness can be reduced by using a stronger polymer in one or more layers (example, in heavy

duty bags). Heterogeneous polymers can be co-extruded with the use of adhesive tie layer

(example LDPE and PA). Use of scrap or reclaim material in the structure to give material cost

savings (example, refuse sacks). It is often only the co-extrusion that high performance polymer

can be used in an acceptable cost\performance ratio (Fox, 1990).

2.5 Meat Products

In developing countries the main process for the preservation of meat is drying with or

without salt and sometimes combined with smoking. Processes for a number of traditional local

varieties have been developed over hundreds of years, but there is no consistent technique which

would ensure that the product will always be of an acceptable quality (FAO, 1985). The purposes

of meat processing include preparing products that would be stored for considerable time periods

at ambient temperatures (Hui, 1999). Processed meats include sausages, cured and smoked, non

26

comminuted meat (ham and bacon), restructured products, and canned products. These processed

meats can be successfully manufactured from beef, pork, lamb, venison, chicken, turkey, and

seafood (Claus et al., 1994).

Traditional techniques for processing meat usually involve salting, drying, and/or

smoking. There is a wide range of meat products, such as Charque and Carne-de-sol in South

America, Nham in Southeast Asia, and Biltong in South Africa, Boucané in Reunion Republic

(Trystram, 2004). The traditional commercial processed meat products in Nigeria can be grouped

into four: the fermented meat products (N’dariko and Jirge), the sun-dried products (Kilishi),

barbecued product (Tsire or Suya and Balangu) and smoke-dried products (Banda) (Okonkwo,

2001). Recently there is the emergence of salted pork meat Unam inung in the Nigerians meat

research (Hui, 2007). These meat products are popular because they are delicious and high-

quality meat specialities (FAO, 1990).

2.6 Salted Meat

Salt (sodium chloride) has three major functions in a meat product: preservation,

promotion of binding properties in proteins and flavouring. Salt is important in preserving dry-

cured meats. Salting and drying, continue to play an important role in the meat marketing

structure of many of the world's less developed countries. Controlled moisture products,

prepared either directly by dehydration or indirectly by increasing extracellular osmotic pressure,

as in the case of curing, may assume a renewed importance in coming years through the

cumulative demands placed upon traditional commercial meat sales systems by an increasingly

sophisticated and centralised industrial sector. Salted and semi-dried meat products which are

popular in their own right, stand up better to the abuses of these distribution networks than their

chilled or fresh meat, counterparts.

Salted meat either dry- or wet-salting can be performed prior to drying. In most cases,

local spices are added to salt. The greatest variety of salted dried meat products can be found in

Africa (Qwanta in Ethiopia, biltong in South Africa, Klioh in North Africa, Odka in Somalia and

Unam inung a salted pork meat from Nigeria). In Latin America, Charque and Carne-do-sol are

well known, particularly in Brazil, and Tassajo is consumed in most South American countries.

Pastirma is famous in Turkey, Egypt and Mediterranean basin. Dendeg giling is an Indonesian

dried meat product prepared by sun drying a mixture of minced beef, salt, garlic, coriander and

sodium nitrite. A North American product is pemmican or beef jerky, which is dried beef often,

27

kept under a layer of lard for better storage and Boucané a traditional meat from Reunion

Republic (FAO, 1990; Poligné et al., 2001; Hui, 2007).

CHARQUE

Charque as described by FAO (1991) consists of flat pieces of beef preserved by salting

and drying. The fresh, raw meat from the fore- and hindquarters is cut into large pieces of about

5 kg, which should not be more than 5 cm thick. The pieces are submerged in a saturated salt

solution for about one hour in barrels or cement vats. On removal from the brine, the meat is laid

on slats or racks above the brine tank to drain.

For dry-salting, the flat meat pieces are piled on a sloping, grooved, concrete floor under

a roof. To form a pile, salt is spread evenly over the floor about 1 cm high. Then a layer of meat

is put on the salt. The meat is covered with another (1 cm) layer of salt followed by adding

another layer of meat, and so on until the alternate layers of salt and meat reach a height of about

1 m. The pile is then covered with a few wooden planks and pressed with heavy stones. After

eight hours the pile is restacked so that the top meat goes to the bottom of the pile. The

restacking process with fresh layers of salt is repeated every day for five days. The salted meat is

then ready for drying. Before initiating drying, the meat pieces are subjected to rapid washing to

remove excess salt adhering to the surface. The meat pieces may also be passed through a pair of

wooden rollers or a special press to squeeze out some surplus moisture and flatten the meat slabs.

The meat is then spread out on bamboo slats or loosely woven fibre mats in a shed or, in

industrial production, exposed to the sun on wooden rails which are oriented north-south, thus

permitting an even solar coverage.

Initial drying, directly in the sun, is limited to a maximum period of four to six hours.

This period of exposure may be subsequently lengthened to a maximum eight hours.

Temperatures in excess of 40°C on the meat surface should be avoided. To ensure even drying

over the extended muscle pieces, the meat is placed on the rails during the morning and removed

again in the afternoon. The meat pieces are exposed to the sun each day over a period of four to

five days. After each period of exposure the pieces are collected, stacked in piles on concrete

slabs and covered with an impermeable cloth to protect them against rain and wind and to hold

the heat absorbed.

When sufficiently dry, the meat pieces are either sold without prior packaging or wrapped

in jute sacks. Plastic sacks are not suitable, because the product still contains a certain proportion

of its original moisture content, and this moisture must be allowed to drain freely from the

28

product. Charque keeps for months under ambient room conditions and is resistant to infestation

by insects and growth of moulds.

BOUCANÉ

Boucané is a traditional meat product from Réunion that is obtained by salting, drying

and hot smoking pork belly. One-step unit operations give rise to a stable product with

remarkable colour and flavour qualities. Mass transfers (salt gain, water loss) stabilize the end

product, which has 28.5% water content and 5.6% salt content. Lipid oxidation and Maillard

reactions are the main mechanisms involved in the boucané production process. The molecules

derived from these two reactions are along with smoke compounds responsible for the flavour

and colour of the end product (Poligné et al., 2001).

UNAM INUNG MEAT PRODUCT

Unam inung is a ready-to-eat pork product that is very popular in the South-South states

of Nigeria. It is most commonly served with cassava chips or boiled yam and plantain. The

product is traditionally prepared by heavily salting sliced pork which is then sun dried and

packed in a dry pot. In some cases the product may also be smoked, when required for

consumption or for the market, the desired quantity is removed from the pot, washed and boiled.

The traditional production techniques have not been improved to cope with modern scientific

requirements and with increasing demand (Hui, 2007). An evaluation of the qualitative effects of

processing on the quality of the meat product Unam inung carried out by Egbunike (2003)

showed that curing reduced moisture and protein contents of pork unlike the lipid content, this

increased. Smoked samples were superior in quality and acceptability of meat products.

Unsmoked ones with those salted at 25% being rated best in all organoleptic attributes. Thus

processing generally improves the quality and acceptability of meat products. Also Ekanem et

al.(1994) reported that sample of unam inung that was cured with 25% NaCl concentration and

smoked had remarkable overall acceptability and sensory properties but changes in protein

contents shows no particular trend.

2.7 Analytical Frameworks

Unlike glass and metal, plastics are permeable. Barrier properties indicate permeability to

water vapour, oxygen, carbon dioxide and other gases. In addition, component of the product can

permeate through the package. Examples include the parabens, flavourants, water vapour and

oils (Yam et al., 1999).

29

Consequently, the presence of an impermeable dispersed phase increases the tortuosity of

the path that a molecule must traverse for permeating through a film. It is useful to discuss this

concept in terms of a tortuosity factor τ, which is an effective path length divided by actual

thickness of the film. Maxwell derived an expression for τ considering the conductivity of a

system in which a conducting phase contains a volume fraction of spherical non-conducting

particles (Paul and Bucknall, 2000):

(1)

The tortuosity is used to calculate the permeability of composites Paul and Bucknall, (2000) in

the following expression:

(2)

Where, Pc, Pm, and φm are the permeability of the composite, the permeability of the matrix,

and the volume fraction of matrix, respectively. Robeson has extended Maxwell's work by

applying it to blends for which both components are permeable (Paul and Bucknall, 2000).

Derived by Robeson, Pc is given by the following equations where polymeric components are

denoted by 1 and 2 subscripts and φi stands for volume fraction of the ith phase.

Series laminate (layers normal to permeant flow):

(3)

Parallel laminate (layers parallel to permeant flow):

(4)

Semi-logarithmic additivity rule for blends is defined

as follows [1]:

(5)

where, φi is the volume fraction of the ith component.

2.8 Prediction of Shelf Life

In order to predict the length of shelf life in relation to the degree of quality of a food, a

knowledge of the rate of deterioration or reaction order as a function of environmental conditions

is necessary. If the initial rate of deterioration is known, then it should be possible to predict the

overall shelf-life. These predictive tests prevent the need for prolonged storage studies on many

samples and therefore save on space and cost (Smith, 1993).

30

Basic reaction kinetics has been applied to prediction of loss of food quality. The loss of

quality for most foods can be represented by

Where A is the quality factor measured; t is the time; k is a constant which depends on the

temperature and water activity; n is a power factor giving the order of the reaction and is the

rate of change of A with (negative, loss of A; positive, production of undesirable end products).

Zero-order kinetics:-

The order of the reaction, n defines whether the rate is dependent on the value of A. Many food

systems are assumed to behave as zero-order reactions (n=0). Thus, the rate of loss is contant

under constant conditions of temperature. Thus

This may be integrated to give

A = Ao –kt or Ae = Ao - kts

where Ao is the initial quality value, A is the quality value at time t. Ae is the value of A at the

end of the shelf-life and ts is the shelf-life in days, months or years.

A may be defined analytically or by taste panel evaluation. If Ao is assumed to be 100% quality,

then

First-order kinetics

Many foods deteriorate by first-order kinetics (n=1), which results in exponential

decrease in the rate of change as the quality decreases. Thus, the rate of quality loss indirectly

dependent on the amount left:

Integration gives:

In (Ae/ Ao ) = -k ts

31

A semi-logarithmic plot of Ae/ Ao against time (t) gives a straight line with slope k. The types of

deterioration which follow first-order kinetics include microbial growth (fresh meat and fish),

microbial production of off-flavours, vitamin losses (canned and dried foods) and loss of protein

quality.

32

CHAPTER THREE

MATERIALS AND METHODS

3.2 Sample/Material Procurement and Processing

The pork was procured from Animal Science Farm, University of Nigeria, Nsukka. The

PP (polypropylene) resins used in this study were manufactured by Eleme Petrochemicals

Company Limited, Rivers State, Nigeria; LDPE (low density polyethylene) resins were from

Seetec LG Chem Limited, Chung-Nam Korea. A local clay pot was sourced from Ogige market,

Enugu state.

3.1. 1 Preparation of Samples/Raw Materials

The LDPE film, co-extruded low density polyethylene/polypropylene (LDPE/PP) film

and PP film produced in this study were made using low density polyethylene extrusion air-

cooled blown film line plant for LDPE and polypropylene extrusion water-cooled blown film

line plant for PP and LDPE/PP of the Chumaco Plastic Industries, Onitsha, Anambra state. The

extruder was fed to a 7.7cm diameter die and all the films were made under the same run

conditions at 45kg/h output rate with 100 micron film gauge using Peacock (0.01x10mm)

model G, micro gauge, Japan. The extruding temperatures for LDPE are 125oC; PP 218

oC; and

LDPE/PP 208oC. For the extrusion of coextruded film, the LDPE and PP resins were mixed in

the ratio of 5:95 (Higgins, 1997).

For the meat sample, a one year old crossbreed (landrace × large white) pig was

slaughtered. Muscles (6.04 kg) were obtained from the region of loin. Brine salting was carried

out by immersing the meat sampling into 25.0% brine solution (w/w) for about 8h (Fig. 1) and

the meat samples were subsequently submitted to solar drying for 4 days to reach a moisture

content of 28.31±0.64%. A quantity of 2.64kg of the loin was measured after drying.

Meat samples were cut into 25g samples, 105 samples were measured out and randomly

subsected to one of the following packaging methods: unpackaged, clay pot, low density

polyethylene film sachet, polypropylene film sachet and coextruded low density

polyethylene/polypropylene film sachet. The experimental films were formed into sachet (15cm

x 5cm), using Impak electric sealing machine, Barcelona. Each sachet was filled with 25g test

meat, sealed and stored in a horizontal position at room temperature for six months. Samples of

different packaging materials were removed every month for analysis.

33

Unam inung processing

Procurement of freshly slaughtered pork

Scalding at 60oC

Removal of connective tissues and visible fat

Refrigeration

Slicing (about 15mm thick)

Marinating (8hrs.) in 25% (w/w) salt solution

Solar drying (40-45oC)

Cooling

Weighing

Packaging

Unpackaged Clay pot LDPE film PP film Co-extruded LDPE/PP

Storage: for six months

Figure1: Flow chart of processing of unam inung meat product

34

3.2 Temperature and Relative Humidity of Storage Room

The temperature and relative humidity of the storage environment of the samples were

monitored daily during storage through recording of the wet and dry bulb temperatures of the

storage at regular interval of two hour between the hours of 8.00 and 18.00 local time. The dry

bulb readings represent room temperature while the relative humidity of the environment was

obtained from the depression in wet bulb readings using psychrometric chart.

3.3 Chemical Analysis of Sample

3.3.1 Moisture Content (AOAC, 1995)

The moisture content was determined by the oven method. A sample (2.0g) was weighed

into a porcelain dish and dried in a vacuum oven at the 700C for 20 hours. The dish was weighed

after drying and the weight loss taken to be the moisture content of the sample this being

expressed as a percentage of the initial weight.

initial weight final weight

moisture % = 100initial weight

3.3.2 Crude protein

The crude protein content of the sample was determined according to the Kjeldahl‟s

method as described in AOAC (1995). One gram sample was weighed and put into the digestion

tube. Twenty millilitres of concentrated sulphuric acid (98%) and a tablet of digestion mixture as

catalyst were added into the digestion tube. The digestion was carried out for 3-4 hours (till the

digested contents attained transparent colour). The digested material was allowed to cool at room

temperature and diluted to a final volume of 75 ml. The ammonia trapped in H2SO4 was liberated

by adding 40% NaOH solution through distillation and collected in a flask containing 4% boric

acid solution, possessing methyl red indicator and titrated against standard 0.01N hydrochloric

acid and quantity of nitrogen calculated from the formula:

35

3.3.3 Fat Content (AOAC, 1995)

Extraction thimble was weighed empty, filled with sample up to half and weighed again.

The mouth of the extraction thimble was plugged with cotton wool to prevent sample from

flowing out. The thimble containing the sample was then placed in the soxhlet extractor.

A flat bottom quickfit flask was weighted empty and filled with petroleum spirit up to

half. The extractor containing thimble and sample was then be fitted into the quickfit flask and

connected to the condenser. The flask was heated with the heating mantle and extraction carried

out for 16 hours after which the petroleum spirit was evaporated out. The weight of flask with oil

was determined after heating in boiling water bath to remove all traces of water, drying over

calcium chloride in the desiccators and cooling.

Weight of thimble empty = Ag

Weight of thimble plus sample = Bg

Weight of sample = (B – A) g

Weight of quickfit flask empty = Cg

Weight of quickfit flask plus oil = Dg

Weight of oil = (D – C) g

Weight of oil in sample (%) = 100

1

D C

B A

3.3.4 Water Activity

The aw-value Analyzer model 5803 of West Germany was used to determine sample

water activity. First, a special filter paper was soaked in a saturated solution of barium chloride

(BaCl2) and placed in the chamber of the aw-meter for three hours to standardize the instrument.

Then ground meat sample was put in the chamber, screwed, and allowed to equilibrate for three

hours. Appropriate temperature adjustments and correction factors before and after the

determination, was effected. The aw-value was taken and recorded.

3.3.5 pH Determination:

pH of the samples were determined according to the method described by Fakolade and

Omojola (2008). The pH meter was standardised by using pH 7 and 4 buffer solution. pH was

measured in the aqueous extract in 1g of the dried samples, homogenized in 10 ml distilled water

using Hanna checker pH meter. The electrode was immersed and readings were taken.

36

3.3.6 Salt (sodium chloride) content (AOAC, 1995).

The sample (3g) was weighed into a 250ml flask and 25ml of 0.5N silver nitrate solution

was added. Then 15ml of concentrated nitric acid was added and the sample was boiled until the

meat dissolved. Then concentrated potassium permanganate solution was added in small

portions, boiling after each addition until KMnO4 colour disappear and solution becomes

colourless or nearly so. Then 25ml of water was added and boiled for five minutes, cooled,

diluted to about 150ml and 25ml diethyl ether was added, shaken and 5ml of ferric ammonium

sulphate solution was added as an indicator. This was titrated with 0.1N ammonium thiocyanate

solution until the solution becomes permanent light brown. Percent salt content was calculated as

follows :

Salt content (%) = [25ml of AgNO3 - Titre (ml of NH4SCN)] x 0.005844 x 100

Weight of sample

3.3.7 Protein Solubility:

The method of Obanu (1978) was used. Some 1g of sample mixed with 50ml of Sodium

Dodecyl Sulphate (SDS) and 1% B-Mercaptoethanol and allowed to stand for 30 minutes at

room temperature. The solution was heated for another 30 minutes and centrifuged at 30,000g.

The residue represents the insoluble fraction. The nitrogen content of each sample (fraction) was

determined using the micro-Kjeldahl distillation technique. The nitrogen content of the filtrate

T1 and the residue 2 was used to calculate the percentage soluble protein.

3.3.8 Thiobarbituric Acid Reactive Substances (TBARS):

This was done by Kirk and Sawyer (1991) method. A portion of the meat sample (10g)

was macerate with 50ml water for 2 minutes and washed into distillation flak with 47.5 ml water.

Concentrated 4 M hydrochloric acid (2.5ml) was added to bring the pH to about 1.5. Also some

glass beads were adding to prevent foaming. The distillation apparatus was then assembled and

the flask heated with the electric mantle at the maximum setting. Heating was continued until

50ml of the distillate was collected. This was thoroughly mixed by shaking.

The distillate was pipetted in duplicate of 5ml into test tubes and 5ml of TBA reagent

(0.2883 g/100ml of 90 percent glacial acetic acid) added. The test tubes were then stoppered,

shaken and heat in boiling water bath for 35 minutes. A blank solution containing 5ml of

37

distilled water and 5ml of TBA reagent was treated similarly. After removal from the water bath,

the tubes were cool in water for 10 minutes and optical density of the solutions determined

against the blank reference at a wavelength of 538nm using Spectro 21D, Pec Medicals USA .

TBARS number. (mg malonaldehyde per kg sample) was then calculatedasfollows: TBARS

number = Optical Density x 7.8.

3.3.9 Free Fatty Acids

This was done by Kirk and Sawyer, 1991 method. Mixtures of 25 ml diethyl ether with 25ml

alcohol and 1 ml phenolphthalein solution (1 percent) were carefully neutralized with 0.1 M

sodium hydroxide. 1-10g of the melted fat were dissolved in mixed neutral solvent and titrate

with aqueous 0.1 M sodium hydroxide shaking constantly until a pink colour that persists for 15

s is obtained.

3.3.10 Vitamin Analysis

3.3.10.1 Vitamin A

The vitamin a content was determined by the method of Arroyave et al (1982). Ten millilitres

(10 ml) of 95% ethanol and an equal volume of hexane were added into a test-tube containing

1g of the sample, followed by the addition of 10 ml of normal saline to dilute it. The test tube

was stoppered and the contents mixed vigorously on a vortex mixer for 2 minutes to ensure

complete extraction of carotene and vitamin a before centrifugation for 10 minutes at 3000xg to

obtain a clean phase separation. Thereafter, 100µl of hexane extract was transferred to a

microcuvette and the absorbance due to carotene at 450nm was read against hexane blank. The

sample was then transferred from the microcuvette to a test tube and the cuvette rinsed with 50µl

hexane and the solution added to the sample in the test tube. The extract was evaporated to

dryness under a gentle stream of nitrogen in a 60oC water bath while avoiding splashing on the

test tube wall. The residue was immediately redissolved in 10µl of chloroform-acetic anhydride

(1:1, v/v) reagent and 100µl of freshly prepared TFA-chloroform chromagen reagent was added.

The solution was rapidly transferred to the microcuvette using a microtransfer pipette. The blank

consisted of chloroform-acetic anhydride mixture and TFA-chloroform chromagen (1:1, v/v)

reagent. A UV spectrophotometer (Spectro 21D, PEC Medicals USA) was used to read the

38

absorbance of the sample at 620nm after 15 seconds (t15) and again at 30 seconds (t30) after

addition of the chromagen. The concentration of vitamin A was read off a standard curve

prepared by diluting vitamin A standard with hexane and the calculation was made as below:

Vitamin A (as µg RE/dl) =

Where = Absorbance reading taken at 620nm

= Absorbance reading at 450nm

= Calibration factor for carotene at 450nm =

= β-carotene correction factor =

= Factor for vitamin A at 620 nm =

In measuring vitamin A, the absorbance correction at 620nm for carotenoids is:

in which the factor of 2 derives from the difference in the dilution of

carotenoids and vitamin A in their respective assays.

3.3.10.2 Vitamin C (Ascorbic acid)

Ascorbic acid was determined using the procedure described by Kirk and Sawyer (1991).

Standard indophenol‟s solution was prepared by dissolving 0.05g 2,6-dichloro Indophenol in

water diluted to 100ml and filtered. To standardize, 0.053g of ascorbic acid was dissolved in

90ml of 20% metaphosphoric acid and diluted with water to 100ml. 10ml of this solution was

pipette into a small conical flask and titrated with indophenol‟s solution until a faint pink colour

persists for 15seconds. 2ml of the broth was pipette into a conical flask and 5ml of 20%

metaphosphoric acid (as stabilizing agent) was added and made up to 10ml mark with water. It

was titrated with the indophenols solution a faint pink colour persists for 15seconds. The vitamin

content in the meat was calculated

39

3.3.10.3 Vitamin E

Vitamin E was determined by the method of Kirk and Sawyer, 1991. About 1g of sample oil was

weighed into a 100ml flask fitted with a reflux condenser. Then 10ml absolute alcohol and 20ml

M alcoholic sulphuric acid were added. The condenser and flask were wrapped in aluminium

foil, reflux for 45 minutes and cool. 50ml water was added, and unsaponifiable matter of the

mixture was extracted with 5 x 30 ml diethyl ether. The combined ether extract was washed and

dry over anhydrous sodium sulphate. The extract was evaporated and the residue was

immediately dissolved in 10ml absolute alcohol.

Aliquots of solutions of the sample and standard (0.3-3.0 mg vitamin E) were transfer to

a 20 ml volumetric flask. Thereafter, 5ml absolute alcohol and 1ml conc. Nitric acid were added

to the flask, the flask was then placed on water bath at 90oC for exactly 3min from the time the

alcohol begins to boil. After removal from the water bath, the flasks were cool rapidly under

running water and adjust to volume with absolute alcohol. The absorbance of the solutions were

determined against the blank reference at a wavelength of 470 nm using Spectro 21D, Pec

Medicals USA.

3.4 Microbial Analysis

Pour plate method as described by Harrigan and Mc Cance (1976) was used.

3.4.1 Total Viable Count

This involves the culturing of the meat extracts in Nutrient agar medium and incubating

at 37oC for 24hrs. 28g of the Nutrient agar was suspended in one litre of distilled water, boiled to

dissolve completely and autoclave at 10psi for 15minutes at 121oC and allowed to cool to 45

oC

before use. A diluent for serial dilution was prepared by dissolving a tablet of Ringer tablet in

500ml of distilled water. This solution was sterilized by autoclaving at 121oC for 15 minutes.

Sterilized disposable petri dishes were used for plating. 1g of minced meat was weighed into a

sterile conical flask containing 9ml of Ringer solution, and the mixture was mixed thoroughly to

give the desired dilution. One ml of each dilution was pipetted in duplicate into sets of sterile

petri dishes and shake to mix thoroughly. The serial dilution was carried out to 10-4

dilution i.e.

1ml of the solution was drawn out using a pipette and was introduced into a second test-tube

containing 9ml of distilled water and this was done serially until the last tube was reached. A

fresh pipette was used at each stage. Sterile Petri dishes were set out for each dilution and they

were labelled with the dilution number. 1ml of each dilution was pipetted into the centre of the

40

appropriate dishes, using a fresh pipette for each dilution. Nutrient agar was poured into each of

the plates, enough to cover the 1ml solution in them. The medium was allowed to solidify, then

inverted and incubated at 37ºC for 24 hours. The numbers of colonies were counted with the use

of a colony counter. The number of microorganism was expressed as colony forming unit per

gram (cfu /g).

3.4.2 Mould Count Determination

This was carried out using sabourand dextrose agar. Sixty-five (65) g of the extract agar

was dissolved in 1000ml of distilled water and sterilized in the autoclave at 10psi for 15minutes

at 121oC. A diluent for serial dilution was prepared by dissolving a tablet of Ringer tablet in

500ml of distilled water. This solution was sterilized by autoclaving at 121oC for 15 minutes.

Sterilized disposable petri dishes were used for plating. 1g of minced meat was weighed

into a sterile conical flask containing 9ml of Ringer solution, and the mixture was mixed

thoroughly to give the desired dilution. One ml of each dilution was pipetted in duplicate into

sets of sterile Petri dishes and shake to mix thoroughly. The serial dilution was carried out to 10-2

dilution i.e. 1ml of the solution was drawn out using a pipette and was introduced into a second

test-tube containing 9ml of distilled water. A fresh pipette was used at each stage. Sterile Petri

dishes were set out for each dilution and they were labelled with the dilution number. 1ml of

each dilution was pipetted into the centre of the appropriate dishes, using a fresh pipette for each

dilution. Sabourand dextrose agar was poured into each of the plates, enough to cover the 1ml

solution in them. The medium was allowed to solidify, then inverted and incubated at ambient

temperature for 72 hours. The numbers of colonies were counted with the use of a colony

counter. The number of microorganism was expressed as colony forming unit per gram (cfu / g).

3.5 Sensory Evaluation of Samples

Unam inung were desalted in water (4 litres of water/kg piece) at ambient temperature for

one hour. The desalted meat samples were cut into a cube of 2.6cm3, wrapped with aluminium

foil and cooked USDA-FSIS (2008) for one hour. Samples were then cooled at room temperature

before presented to a 10-man panel of judges drawn from postgraduate students of Food Science

and Technology Department, University of Nigeria, Nsukka.

The meat cuts were evaluated according to Miller (1994) research on sensory

measurement of meat product. Unam inung were evaluated for juiciness, tenderness, flavour

intensity and colour on an 8-point hedonic scale (appendix I). Samples were coded with random

41

numbers and were then served to the panelists on glass sauce. Each treatment replication was

evaluated at 1, 2, 3, 4, 5 and 6 months.

3.6 Statistical Analysis

The experimental design was completely randomized design. The significance of

differences among samples at each month of storage was determined by Analysis Of Variance

(ANOVA) using the Duncan‟s Multiple Range Test of General Linear Model procedure of SPSS

(SPSS, 2007). Differences were considered significant at the p<0.05 level. Also correlation

analysis was used to establish relations between variables at the p<0.01 levels.

3.7 Microstructure Characterisation

The microstructures of the films were characterized on a Motic Image Plus 2.0ML

polarized light optical microscopy (x100) made by Motic China Group. The microscope is

additionally equipped with digital camera. Films of 100µm thickness were viewed.

3.8 Coefficient of Friction

Coefficient of friction was tested using ASTMD 1894 method (2008). The films

coefficients of friction were determined when the films were sliding over a stationary sled with a

moving plane at ambient temperature.

42

CHAPTER FOUR

RESULTS AND DISCUSSION

4.1 Storage Temperature and Relative Humidity

Table 3 presents the temperature and relative humidity data for the period of the study.

Months 1 and 2 storage temperatures were significantly (p<0.05) higher than other months of

storage, while the relative humidity of the same periods were significantly lower than other

periods. This is because they are months of April and May which marks the beginning of the

rainy season of the year in Nigeria. The total mean amount of temperature and relative humidity

of the storage period were 28.64±1.39 and 72.47±5.00 respectively. A specific set of storage

conditions must exist before a reaction is initiated in a stored food. Generally, the higher the

temperature and humidity in the storage area, the more rapid the chemical attack. However,

shelf-life is limited by water-vapour loss, which is diminished in the presence of high humidity

(Rabinow and Roseman, 2000). Extremes of temperature can cause deterioration to product

and/or pack. Higher temperatures generally represent an acceleration effect. A high temperature

coupled with a high relative humidity will produce a shower effect if the temperature is lowered

sufficiently to reach dew point. Contamination from liquid moisture can then encourage mould

and bacterial growth. Table 3 also illustrates the inverse relationship between temperature and

relative humidity. High temperatures are associated with lower relative humidity because high

temperature increases the moisture carrying capacity of the air, and hence lower relative

humidity. The reverse is the case with lower temperatures.

43

Table 3: Room mean monthly temperature and relative humidity readings

Storage time (months) Temp.oC Relative Humidity (%)

1 27.67±1.07b 69.55±2.90

de

2 27.91±1.18a 68.29±3.55

e

3 26.55±1.25c 73.03±4.69

c

4 25.95±0.72e 75.13±3.64

b

5 26.34±0.72d 77.42±4.69

a

6 26.58±0.94c 71.17±3.67

cd

Grand mean 26.83±1.39 72.47±5.00

Values are means determinations ±SD, a,b,c,d,e

Values in the same column with the same letter are not significantly different (p>0.05).

4.2 Mechanical Properties

Coefficient of friction or slip

Table 4 shows the coefficient of friction of the experimental plastic films. This shows

that the coextruded film LDPE/PP had a high coefficient of friction of 0.29 which was

significantly (p<0.05) higher than PP film (0.26) and PE film (0.25). After heat treatment of the

LDPE/PP coextruded sample above the melting point of LDPE but below that of polypropylene

and subsequent blow cooling at room temperature. A significant increase was recorded for the

mechanical properties of coefficient of friction (Wool, 1995). Coefficient of friction relates to the

ease with which one material will slide over another. Passage of films through packaging

machinery requires high coefficient of friction to prevent binding and is important in form, fill-

seal operations (Rabinow and Roseman, 2000).

Table 4: Coefficient of friction

LDPE PP LDPE/PP

0.25±0.02b 0.26±0.01

b 0.29±0.02

a

a,b Values in the same row with the same letter are not significantly different (p>0.05).

LDPE: Low Density Polyethylene, PP: Polypropylene, LDPE/PP:

Coextruded Low Density Polyethylene/Polypropylene.

44

Film contraction

After film blowing in the 7.7cm die, it was found that the coextruded LDPE /PP film

contracted to 7.1cm in width while PP and LDPE were measured to be 7.7cm in width. Both PE

and PP are semi crystalline polymers with a spherulitic structure. Voids and defects are induced

by the density change due to crystallization occurring in the melt which causes volume

contraction for PP up to 10% (Wool, 1995). The volume contractions associated with the random

nucleation of spherulites near the interface have the effect of pulling the outer polymer in liquid

phase across the interface and creating interspherulitic influxes (Wool, 1995).

Photomicrographs of the plastic Films

The micrographs of experimental plastic films are shown in Fig 18. The overall

molecular orientation of PP and LDPE was not different in co-extruded films; similar result had

been reported by Gururajan (2007). Increase of the PP matrix modulus is a consequence of the

change in the PP crystalline structure due to presence of highly crystalline polyethylene particles

(Vlassov and Kuleznev, 1995). The polyethylene crystals were found to nucleate PP, increasing

the number of spherulites and reducing their sizes. The finer micro-morphology again resulted in

improvement of the overall mechanical performance (Utracki and Dumoulin, 1995).

Low Density Polyethylene Polypropylene (PP) Coextruded (LDPE/PP)

(LDPE)

45

Figure 2: Micrograph of the experimental plastic film X 100.

Table 5: Correlation matrix of the parameters studied in unam inung

TVC MC pH aw TBA CF FFA CP NaCl VITA VITE SP VITC TEMP RH

TVC .420**

.723**

.828**

.353**

-.070 .334**

-.676**

-.373**

-.217 -.357**

.729**

-.097 -.059 .068

MC .551**

.662**

.459**

-.144 .687**

-.778**

-.990**

-.290* -.528

** .679

** -.204 -.399

** .337

**

pH .636**

.148 .175 .346**

-.744**

-.519**

-.044 -.228 .852**

.096 -.128 .064

aw .515**

-.158 .571**

-.700**

-.629**

-.390**

-.474**

.680**

-.262* -.248 .245

TBA -.742**

.770**

-.250 -.446**

-.882**

-.753**

.268* -.743

** -.640

** .440

**

CF -.611**

.072 .127 .783**

.783**

-.078 .822**

.578**

-.388**

FFA -.469**

-.649**

-.794**

-.831**

.497**

-.586**

-.669**

.359**

CP .766**

.018 .475**

-.861**

.140 .106 -.104

NaCl .255* .501

** -.626

** .215 .362

** -.322

*

VITA .736**

-.161 .731**

.744**

-.464**

VITE -.444**

.762**

.579**

-.371**

SP -.058 -.319* .189

VITC .512**

-.404**

TEMP -.765**

RH 1

**. Correlation is significant at the 0.01 level (2-tailed).

*. Correlation is significant at the 0.05 level (2-tailed).

TVC –Total Viable Count; MC-Moisture Content; aw-Water Activity; TBA-Thiobarbituric Acid Reactive

Substances; CF-Crude Fat; FFA-Free Fatty Acid; CP-Crude Protein; SP-Soluble Protein; RH-Relative Humidity. TEMP- Temperature; VITA-Vitamin A; VITE-Vitamin E; VITC-Vitamin C.

4.3 Results on Chemical Analysis of Samples

Moisture

The moisture content of unam inung after processing was 28.31±0.64 (Table 6). Results

obtained for moisture content of unam inung fell within the range of ambient–stored salted meat

reported by Burfoot et al., (2010). During storage, the trends of changes in moisture content of

samples were variable (Fig. 2). While the unpackaged samples and those packaged in the clay

pot slightly increased in moisture content, those packaged in PP, LDPE and PP/LDPE

significantly reduced in moisture in the first 2 months of storage. Within this period, unpackaged

46

samples increased slightly to 29.21%, clay pot packaged samples reduced slightly to 27.87%,

LDPE significantly reduced to 25.01%, PP packaged samples significantly reduced to 23.95%

and LDPE/PP packaged samples significantly reduced to 24.40% (see Appendix II Table A ).

Whereas unpackaged samples had the highest increase, the PP packaged samples had the highest

decrease. Thereafter, all samples increased in moisture content. Throughout the storage period

unpackaged samples maintained the highest moisture content and the co-extruded low density

polyethylene/polypropylene maintained the lowest moisture content. These results show that

exchange of moisture was taking place between the packaged samples and the environment of

storage. The extent of this moisture exchange depended on the porosity of the packaging

materials. The LDPE and PP/LDPE packaging materials were more effective in preventing

moisture exchange while the unpackaged and the clay pot packaging materials were least

effective.

The trends of changes in moisture content of the products appear to depend on the

relative humidity of the storage environment. The first two months of storage was within the

period of reducing relative humidity (Table 3). Hence, samples lost moisture to the atmosphere.

The later storage period corresponded to period of increasing relative humidity (Table 3). Hence,

samples were gaining moisture from the storage environment, irrespective of the packaging

material. It is well known that food samples stored in an environment of lower relative humidity

would lose moisture to the atmosphere whereas those stored in an environment of higher relative

humidity will gain moisture from the environment. It can be seen from the result that with

prolonged storage, under high relative humidity environment, the products would gain enough

moistures to the point of raising water activity and encouraging spoilage.

47

Table 6: Quality characteristic of freshly prepared Unam inung

Values are means of duplicate determinations±SD

Parameter Value

Moisture content (%) 28.31±0.64

Ash (%) 11.49±0.19

Crude fat (%) 14.08±0.04

Crude protein (%) 29.43±0.01

Soluble protein (%) 39.00±0.05

NaCl (%) 8.77±0.05

Water activity 0.84±0.00

pH 6.15±0.00

Thiobarbituric Acid Reactive Substances

TBARS (MgMA/kg)

0.32±0.01

Free fatty acid( % oleic acid) 0.22±0.01

Vitamin A (as µg/g retinol) 9.18±0.01

Vitamin E (as mg/100g tocopherol) 0.225±0.00

Vitamin C (as mg/100g ascorbic acid) 14.76±0.08

Total viable count TVC (Cfu/g) 5.1 x 104±14.14

Coliform count (Cfu/g) 1.7 x 102±14.14

Mould count (Cfu/g) 6.0 x 10±0.00

48

Key:

Figure 3: Changes in moisture content (%) of unam inung stored with different packaging

materials for six months at ambient temperature.

Protein

The crude protein percent of unam inung after processing was 29.43±0.01 (Table 6).

Results obtained for crude protein content of unam inung fell within the range of processed pork

meat reported by FAO (2007) and NIF (2007).

Crude protein percent of unam inung samples were found to be variable (p<0.05) in all

samples (Figure 4 & Appendix II Table B). During storage, the mean crude protein content of the

samples was 31.11±2.23 at first month of the storage. Nonetheless, protein content of the products

remained high during storage. This agrees with the finding of Garcia et al. (2001) that despite the

conditions of salted meat processing, it keeps its high protein quality. The polypropylene film

sample contained the highest quantity of crude protein (33.82%) while the unpackaged sample

contained the lowest quantity of crude protein (28.39%) which differed significantly (p<0.05)

among the samples. At the end of the storage period, the crude protein decreased to the levels of

28.65±1.06% for all the plastic film packages. It is probable that changes in protein content during

49

storage are related directly to changes in moisture content and inherently to changes in relative

humidity. The crude protein has been shown to be significantly correlated (p<0.05) to moisture

content (r = -0.78) (Table 5). It implies that increase in moisture content, as a result of increase in

relative humidity, caused dilution of the protein content and hence lowers percent protein content

as seen in the later storage period. On the other hand loss of moisture, as a result of lower relative

humidity, caused increase in protein content due to concentration effect, as seen in the first two

months of storage.

Key:

Figure 4: Changes in crude protein content (%) of unam inung stored with different packaging

materials for six months at ambient temperature.

Crude Fat

The crude fat content of unam inung after processing was 14.08±0.04 (Table 6). Results

obtained from crude fat `content of unam inung fell within the range of processed pork meat

reported by FAO (2007). Crude fat decreased with increase in duration of storage (p<0.05) in all

samples (Figure 5 & Appendix II Table C). The mean crude fat percent of the samples was

50

13.91±0.17 at first month of the storage and the clay pot sample contained significantly (p<0.05)

the highest quantity of crude fat (14.08%) while the low density polyethylene film sample

contained significantly the lowest quantity of crude fat (13.63%). At the end of the storage period,

the mean crude fat percentage decreased to the levels of 12.16±0.44% for all the plastic film

packages at the end of the storage. There was significant difference (p<0.05) among the

percentage crude fat content of the plastic films samples at the end of the storage period. The

coextruded Low Density Polyethylene/Polypropylene contained the highest percentage of crude

fat (12.53%) while the low density polyethylene sample contained the lowest percentage of crude

fat (11.68%).

The reduction in crude fat content can be attributed to dilution effect resulting from

increasing moisture content. Also the reason for lower fat content of the plastic films compared to

the clay pot could be attributed to absorption of some of fatty substances in the food by the plastic

films leading to their losses. It is known that fat soluble organic substances such as aromatic oils

and fats are readily dissolved in non-polar polymers such as polyethylene and polypropylene

(Olafsson et al., 1995).

51

Key:

Figure 5: Changes in crude fat content (%) of unam inung stored with different packaging

materials for six months at ambient temperature.

Water activity

The water activity value of unam inung after processing was 0.84±0.01 (Table 6). The

initial water activity of this product was low enough to inhibit microbial growth and spoilage,

except the most osmophilic/xerotolerant moulds/yeasts. This water activity of the product,

however, can be altered during storage abuse such as storage under high relative humidity

environment. This aw value was similar to values reported by FAO, (1985). The mean water

activity values of unam inung samples were found to be variable (Figure 6 & Appendix II Table

D). During storage, the water activity of all samples increased. For example, the mean water

activity of the samples increased to 0.88±0.02 in the first month of storage. The unpackaged

sample contained the highest values of water activity (0.91) which was significantly higher

(p<0.05) than other packaging materials which collectively had 0.87 each. At the end of the

storage period, the water activity values increased to the levels of 0.87±0.01 for only packaged

films. Products in the other packaging materials also increased in aw .The co-extruded low

52

density polyethylene/polypropylene sample had the lowest water activity (0.86) while the low

density polyethylene sample had the highest water activity value (0.88) among the films.

The water activity values have been shown to be significantly (p<0.01) correlated with

changes in moisture content (r = 0.66) and NaCl (r = - 0.63). Therefore samples that had higher

moisture content (e.g. unpackaged and clay pot packaged samples) had higher water activity

while samples with lower moisture content (e.g. PP, LDPE and PP/LDPE packaged samples) had

lower water activity. The influence of NaCl may be indirect and is related to the extent of its

influence on moisture content. Increase in concentration of sodium chloride as moisture is lost

will definitely reduce water activity whereas dilution/reduction of sodium chloride percentage as

moisture is increased/gained by samples will definitely had to increase in water activity as shown

in this study.

Water activity is an index that reflects the availability of water for biochemical reactions

(e.g. lipid oxidation, enzymatic reactions, maillard reactions) and microbial growth. Therefore,

water activity is a very useful parameter for use as a guide to predict food spoilage (Van Den

Berg and Bruin, 1981). At aw above 0.75, water content equilibrium increased with the increase

in NaCl content and the decrease in temperature and consequently the meat in equilibrium would

be modified (Comaposada et al., 2000). Reduced moisture level causes low water activity level.

This might be why there was no decrease in water activity with increase in storage period. The

knowledge of water activity is a very important factor to guarantee the required stability towards

microbial spoilage of the product and to ensure safety by avoiding any threat to the health of the

consumer (Comaposada et al., 2000).

53

Key:

Figu

re 6: Changes in water activity of unam inung stored with different packaging materials for

six months at ambient temperature.

pH

The pH of the products after processing was about 6.15(Table 6). This is within the low

aw food range. This range is capable of supporting the growth of many microorganisms.

However, the low moisture content, water activity and the high salt content will tend to be

inhibitory. During storage (Fig. 7& Appendix II Table E) the pH values of the unpackaged and

those packaged in clay pot increased significantly (p<0.05) from 6.15 to about 6.8 for the clay pot

packaged samples. On the other hand, samples packaged in PP, PP/LDPE and LDPE reduced

slightly during storage. The pH changes in meat are associated with changes in the protein of

meat. The results suggest that both protein hydrolysis (which increases pH) and crosslinkage

(which reduces pH) were occurring in the samples during storage, the resultant pH being

dependent on the reaction dominating in the sample. It is, therefore, seen that in the unpackaged

and clay pot packaged, the dominating reaction is protein hydrolysis leading to increase in pH. In

plastic film packaged samples protein crosslinkage is the dominating reaction, leading to

54

depressing of pH. These reactions are dependent on moisture content and the associated water

activity. The pH is significantly (p<0.05) correlated with moisture content (r = 0.55) and water

activity (r = 0.636). Therefore, unpackaged samples and those packaged in clay pot, which were

higher in moisture and water activities were hydrolysing faster than the crosslinkage reactions and

the net effect is increase in pH due to release of amino groups into the system. Those packaged in

plastic films had lower moisture and water activities, with crosslinkage dominating and the net

effect is removal of amino groups from the system, leading to depression of pH.

Key:

Figure 7: Changes in pH of unam inung stored with different packaging materials for six months

at ambient temperature.

NaCl

The salt content of the samples after processing was about 8.77±0.05% (Table 6). This

quantity (in addition to other preservative characteristics of the product) will be capable inhibiting

many microorganisms capable of spoiling the product. During storage, the salt contents of the

samples decreased (Fig. 8 & Appendix II Table F). For example, the mean NaCl content

55

(percentage) values of unam inung samples was 8.77±0.05 at the beginning and then decreased to

the levels of 8.36±0.48% for all the plastic film packages at the end of the storage (Fig. 8&

Appendix II Table F). Samples packaged in the clay pot and the unpackaged samples similarly

reduced. However, the unpackaged and clay pot packaged samples reduced more than those

packaged in the plastic films. The changes in salt content appear to be dependent on the changes

in moisture content. The NaCl percentage have been found to be significantly (p<0.01) correlated

(Table 5) with changes in moisture content (r = 0.99). The variation in salt content could be

attributed to concentration and dilution effect by the moisture content of the samples. Therefore,

in the first two months of storage, when the samples in the plastic films were losing moisture, the

salt content was increasing due to concentration effect; and when the samples were gaining

moisture the salt contents were reducing due to dilution effect.

56

Key:

F

igure 8: Changes in NaCl content (%) of unam inung stored with different packaging materials for

six months at ambient temperature.

Protein solubility:

The protein solubility values of unam inung samples after production was in the range of

39.00±0.05%. This appears to be low when compared to the data of Okonkwo et al (1992a&b)

and suggests low nutritive value (Okonkwo et al., 1992a,b). During storage, the changes in

protein solubility were different for different packaging materials (Fig. 9 & Appendix II Table G).

For example, the soluble protein of the samples was 39.00±0.05% at the beginning of storage and

this reduced to the average levels of 38.74±0.20 for the plastic film packages at the end of the

storage. On the other hand, the unpackaged and clay pot packaged samples were increasing in

protein solubility with increase in storage time. Protein solubility percentage have also shown

(Table 5) to be significantly (p<0.01) correlated with changes in pH (r = 0.85), moisture content (r

= 0.679) and water activity (r = 0.68). As explained earlier under pH changes, the influence of

moisture content and water activity on protein solubility is to the extent they allow protein

57

hydrolysis/crosslinkage to take place. As these two reactions hydrolysis and crosslinkage are

taking place in meat samples, higher aw/moisture will favour hydrolysis with consequent increase

in pH and solubility whereas lower moisture/aw will favour crosslinkage with consequent

reduction in pH and solubility. This is why the unpackaged and clay pot packaged samples with

higher moisture/water activity were increasing in protein solubility (Fig. 9) and pH (Fig. 7) due to

protein hydrolysis whereas the samples packaged in plastic films, which had lower moisture/water

activity were reducing in protein solubility (Fig. 9) and pH (Fig.7). It even appears that later

increase in moisture content from 3rd

month of storage (Fig. 3) was not sufficient to cause protein

hydrolysis to dominate in these plastic film packaged samples.

Key:

F

igure 9: Changes in protein solubility (%) of unam inung stored with different packaging

materials for six months at ambient temperature.

TBARS

58

The TBARS was low (0.32±0.01mgMA/kg sample) after production (Table 6). This is far

below 2.0 mgMA/kg sample recommended as the maximum acceptable limit in relation to off-

odour/flavour and colour. Thus the products were not rancid after production. During storage, the

TBARS significantly increased throughout storage (Fig. 10 & Appendix II Table H). For

example, the mean TBARS values of the samples increased to about 1.02±0.38 on the average in

the first month of the storage. The unpackaged sample significantly (p<0.05) contained the

highest values of TBARS (1.66) while the polypropylene film sample contained the lowest

TBARS values (0.74). At the end of the storage period, the mean TBARS values increased to the

levels of 3.60±1.05 for only packaged films. The unpackaged and clay pot packaged samples

similarly increased significantly. The co-extruded low density polyethylene/polypropylene

sample had the lowest TBARS values (2.57) while the low density polyethylene sample had the

highest TBARS values (4.67).

The TBARS value is generally regarded as a good indicator of the degree of deterioration

of the organoleptic characteristics of meat as a result of oxidation. This increase in TBARS

values throughout the storage period might be due to the lipid oxidation attributed to oxygen

permeability of packaging material (Brewer et al., 1992). This was in agreement with the

findings of Reddy and Rao (1997). The TBARS have been shown (Table 5) to be significantly

(p<0.01) correlated with changes in NaCl (r = - 0.45); Vitamin A (r = - 0.88); Vitamin C (r = -

0.74) and Vitamin E (r = -0.75). Thus, while NaCl would be promoting oxidation of meat

constituents by oxygen, vitamins A, E and C, which are antioxidant vitamins, would be

inhibiting the oxidation of the meat constituents.

The concentration of TBARS in the coextruded Low Density Polyethylene/Polypropylene

sample film samples were significantly lower (p<0.05) than the polypropylene film and

polyethylene films samples at end of the storage period, indicating protection of meat by the

59

coextruded film packaging. It must be emphasized that all the samples of unam inung packaged

with coextruded LDPE/PP film had TBARS values lower than 2.0 mg MA/kg at 5 months of

storage, and, according to Greene and Cumuze (1982), 2.0 mg MA/kg is the maximum

acceptable unit of TBARS formation due to its relation to off-odour appearance. It had been

shown by Vlassov and Kuleznev (1995) that the dispersed polyethylene particles in the

polypropylene matrix reduced the polypropylene spherulite size, so that the polyethylene

particles may be considered as nucleating agents. Increase of the polypropylene matrix modulus

is a consequence of the changes in the polypropylene crystalline structure due to presence of

highly crystalline polyethylene particles which is followed by a sharp increase of the degree of

polypropylene orientation and also film stability to irradiation. Increase of thermostability and

oxidation resistance as a characteristic for drawn polypropylene films with small amounts of

polyethylene (Vlassov and Kuleznev, 1995).

Key:

Figure 10: Changes in TBARS of unam inung stored with different packaging materials for six

months at ambient temperature.

FFA

60

The FFA after processing of the products was low (0.22±0.01). This suggests little or no

fat hydrolysis after production and before storage. Free fatty acids increased with increase in

storage period (p<0.05) in all samples (Figure 11& Appendix II Table I). The mean FFA of the

samples increased from 0.22±0.01 (as oleic acid) at the beginning of storage to the levels of

0.60±0.09 at the end of storage for the plastic film packages. The FFA have been shown (Table

5) to be significantly (p<0.01) correlated with changes in moisture content (r = 0.68); temperature

(r = - 0.58) and relative humidity (r = 0.63). Increased in FFA values with storage have been

reported by Ogunsola and Omojola (2008). Hydrolytic rancidity is caused by hydrolysis of

triglycerides in the presence of moisture, and gives rise to the liberation of free fatty acids (FFA)

(Rossell, 1999). Samples with higher moisture content (such as unpackaged) had higher FFA

compared to samples with lower amounts of moisture (such as the PP/LDPE packaged samples).

High temperatures can accelerate the reactions with most oils; acidity begins to be noticeable to

the palate when FFA calculated as oleic acid at about 0.5-1.5% and beef at about 1.2% (Kirk and

Sawyer, 1991).

61

Key:

Figure11: Changes in FFA of unam inung stored with different packaging materials for six

months at ambient temperature.

Vitamin A

The retinol content of samples soon after production was 9.18±0.01µg/g. During storage,

the mean retinol content of the samples decreased with increase in storage period (p<0.05) in all

samples (Figure 14 & Appendix II Table L). The mean retinol of the samples which was

9.18±0.01µg/g at the beginning decreased to the levels of 2.11±0.17µg/g on the average for the

plastic film packages at the end of the storage. The retinol value have been shown (Table 5) to be

significantly (p<0.01) correlated with changes in FFA (r = 0.79) and TBARS (r = 0.88). This

means that the vitamin is depleted as it plays its antioxidant role. No significant differences could

be found (p>0.05) between packaging materials. Thus, depletion of vitamin A (retinol) is similar

irrespective of the packaging materials.

62

Key:

Fig

ure 14: Changes in vitamin A content of unam inung stored with different packaging materials for

six months at ambient temperature.

Vitamin C

The vitamin C content of the products was 14.76±0.08 mg/100g sample. During storage,

the ascorbic acid decreased with increase in storage period (p<0.05) in all samples (Figure 13&

Appendix II Table K). For example, the vitamin C of the samples decreased to the levels of

9.78±2.53 for the plastic film packages at the end of the storage. It must be emphasized that at 5

months storage, clay pot sample had the highest value of ascorbic acid which are statistically

different (p<0.05) from plastic film samples. The ascorbic value have been shown to be

significantly (p<0.01) correlated with changes in FFA (r = 0.49) and TBARS (r = 0.72). Ascorbic

acid has been also considered for extending the retail display life of meat (Wheeler et al., 1996).

Ellioth (1999) reported that ascorbic acid act as singlet oxygen quencher, exerting a synergistic

effect when used in combination with other antioxidants like vitamin E. According to them,

63

ascorbic acid acted both as an antioxidant and prooxidant depending on the concentration used

and appeared to have a synergistic effect with other antioxidants.

Key:

Figure 13: Changes in vitamin C of unam inung stored with different packaging materials for six

months at ambient temperature.

Vitamin E

The vitamin E content of the products was about 0.225 (Table 6) at the beginning of

storage. However, the tocopherol decreased with increase in storage period (p<0.05) in all

samples (Figure 12 & Appendix II Table J). This is not unexpected since vitamin E, an

antioxidant vitamin, is destroyed as it plays its role of protecting food constituents from

oxidation. For example the mean vitamin E content of the samples decreased to the levels of

0.20±0.01, on the average for the plastic film packages at the end of the storage. The unpackaged

also reduced significantly more than those packaged. Earlier result on vitamin E of pork

(Longissimus dorsi muscle) has 2.015 mg/kg vitamin E (Lahucky et al., 2006). The tocopherol

value have been shown to be significantly (p<0.01) correlated with changes in FFA (r = -0.83)

and TBARS (r = - 0.75). This implies that increase in TBARS is associated with reduction in

tocopherol content. Tocopherols are the most important natural antioxidant which has a potent to

64

inhibit lipid oxidation by trapping peroxy radicals (Farag et al., 2003). Many workers have

shown that the rate and extent of lipid oxidation are dependent on the vitamin E concentration in

the tissues (Gheisari et al., 2010).

Key:

Figure 12: Changes in vitamin E of unam inung stored with different packaging materials for six

months at ambient temperature.

4.4 Microbial Analysis Results

Total Viable Count (TVC)

The total viable count of unam inung after processing was 5.1x104±14.14 (Table 6). The

mean TVC values of unam inung samples were found to be variable (Figure 15 & Appendix II

Table M). Total viable count had initial increase in all the samples in the first month of storage.

The mean total viable content of the samples was 5.20 x 105±1.79 in the first month of the

storage, the unpackaged sample significantly (p<0.05) contained the highest total viable count

(8.30 x 105) compared to the co-extruded film packaged sample which contained the lowest total

65

viable count (3.85 x 105). Thereafter, TVC continued to increase with increasing time (p<0.05)

in unpackaged and clay pot packaged samples while it started to decrease with increasing time in

samples packaged with plastic films. As shown in Table 5, the changes in TVC appear to be

influenced by changes in water activity (r = 0.83) and pH (0.72). This implies that increasing

water activity in the first month of storage in all samples and subsequent months of storage in the

unpackaged and clay pot packaged encouraged microbial growth which subsequently caused

increase in pH. On the other hand the reducing water activity in the plastic film packaged

samples inhibited the growth of microorganisms with consequent reduction in pH. The extent of

oxygen availability would not be ruled out in explaining the differences in microbial growth

between the plastic films and the unpackaged/clay pot packaged samples. It is probable that the

samples which were not packaged had unlimited access to air (oxygen) which appeared to favour

the growth of aerobic organisms; hence continued increase in TVC in the unpackaged sample

throughout storage. In clay pot packaged sample, enough air (oxygen) was also available (but in

less quantity compared to the unpackaged sample), causing also continued increase in TVC

throughout storage. In contrast, the plastic films had sufficient barrier to air (oxygen)

transmission. Consequently, once the initial oxygen was used up in the first one month of

storage, there were little or no oxygen available to support the growth of the organisms in the

second and subsequent months of storage, resulting to decline in growth and/or death of

organisms in the plastic film packaged samples. Among the plastic film packages, the co-

extruded low density polyethylene/polypropylene contained the lowest quantity of total viable

count while the low density polyethylene sample contained the highest quantity of total viable

count. The clay pot sample had an unacceptable total viable count of 1.20 x 106 which made the

clay pot sample to be discarded and further analysis discontinued.

66

FAO (1991) stated that the total viable count of bacteria (TVC) expressed as organisms/g

on fresh meat or a meat product sets a limit to its shelf-life and that meat will “spoil” with TVC at

106/cm

2 because off-odours; slime and discoloration appear at 10

8/cm

2.

Studies have found out that microorganism counts reduce during storage of salted meat

such as chaque and jerky (Burfoot et al., 2010; Porto-Fett et al., 2009; Torres et al., 1994).

Mould count

Initial mould count after processing was about 6.0x101 cfu/g (Table 6). This continued to

decrease till the end of storage (Fig. 16& Appendix II Table N) in the packaged samples but

increased in the unpackaged samples. This is not unexpected because most moulds are aerobic in

nature. Thus, they were able to grow in the unpackaged samples because of the abundance of

oxygen. On the other hand, packaging limited the amount of oxygen available for the organisms

in the packaged samples and the consequence was lack of growth. This is why the PP/LDPE co-

extruded plastic film recorded the least growth of mould because it has the least permeability to

moisture and air.

Key:

Fig

ure 15: Changes in total viable count of unam inung stored with different packaging materials for

six months at ambient temperature.

67

Key:

Fig

ure 16: Changes in mould count of unam inung stored with different packaging materials for six

months at ambient temperature.

4.5 Organoleptic Characteristics

Juiciness

A significant (p<0.05) storage effect was observed for juiciness of the packaged samples

which tended to increase as storage time increased (Table 10). This may be due to moisture

absorption resulting from the overburdening of the gas barrier of the plastic films by the increased

water vapour in the atmosphere as the storage period progressed to the peak of rainy season. This

result agrees with those of Odigbo and Ikeme (2009). Plastic films samples and clay pot samples

were significantly (p<0.05) lower than the unpackaged sample throughout the storage period.

There was no significant difference (p>0.05) between clay pot and plastic films samples.

Tenderness

Test panel rating for tenderness (Table 10) shows that increase in storage period had no

significant difference (p>0.05) on the unam inung samples. Plastic films and clay pot samples

68

were significantly (p<0.05) lower than the unpackaged samples throughout the storage period.

There was no significant difference (p>0.05) between clay pot samples and plastic film samples.

Flavour intensity

The flavour intensity of the product did not exhibit significant (p>0.05) change in all the

clay pot and plastic films samples with increase in storage time; while the unpackaged samples

flavour intensity decreases significantly (p<0.05) with increase in storage period. This indicates

that the level of rancidity and microbial growth were not high enough to seriously effect the

flavour intensity of the packaged unam inung. Odigbo and Ikeme (2009) also reported that taste

of kilishi product packaged in plastic films did not exhibit significant (p>0.05) changes with

storage period. Fat oxidation as indicated by increased TBARS values in unpackaged stored

unam inung might be the reason for getting lower flavour and colour scores (Tarladgis et al.,

1960).

Colour

There was no significant changes (p>0.05) in colour among all the samples with

exception of the unpackaged samples during storage period (Table 10). But there was significant

decrease (p<0.05) in colour with increase in storage time of clay pot, LDPE and LDPE/PP plastic

films. A decrease in colour score of meat products with increase in storage period had been

reported by Bhat et al. (2011). The decline in colour scores during ambient storage was due to

lipid oxidation and subsequent oxidized compounds reacting with amino acids during non-

enzymatic browning of the product (CheMan et al., 1995).

69

Table 10: Sensory characteristics of unam inung over a 6 months storage period with

different packaging materials

Storage

(months)

Unpackaged Clay Pot LDPE

film

PP film LDPE/PP

film

JUICINESS

1 6.0±0.47az

5.1±0.74cy

5.3±0.67by

5.0±0.47by

4.9±1.20by

2 6.0±0.67az

5.2±1.03bcy

5.2±0.42by

5.0±0.67by

4.9±0.32by

3 6.7±1.06 az

5.8±0.42abcy

5.7±0.48by

5.6±1.07aby

5.5±0.97aby

4 - 5.9±0.74abz

5.8±0.92bz

5.7±0.95abz

5.7±0.67az

5 - 6.3±0.67az

6.5±0.97az

6.1±0.74az

6.0±0.82az

6 - - 6.8±0.63az

6.4±1.96az

6.2±0.63az

TENDERNESS

1 7.0±0.47az

6.3±0.95ay

6.3±0.48ay

6.2±0.63ay

6.1±0.32ay

2 7.0±0.67az

6.2±1.23ay

6.2±0.63ay

6.1±0.57ay

5.9±0.57ay

3 7.3±0.48az

6.3±0.48ay

6.3±1.16ay

6.2±0.79ay

6.1±0.57ay

4 - 6.6±0.52az

6.6±0.70az

6.4±0.70az

6.3±0.95az

5 - 6.9±0.74az

6.8±0.79az

6.6±0.52az

6.5±0.53az

6 - - 6.7±0.48az

6.5±0.53az

6.3±0.67az

FLAVOUR

1 5.9±0.74az

6.2±1.69az

6.2±0.92az

6.3±0.67az

6.4±0.70az

2 5.0±0.67by

6.0±0.67az

6.1±0.88az

6.2±0.79az

6.3±0.67az

3 4.9±0.57by

5.9±0.88az

6.0±0.94az

6.1±0.57az

6.3±0.82az

4 - 5.9±0.57az

6.0±1.15az

6.2±0.63az

6.2±0.63az

5 - 5.5±0.71az

5.6±0.84az

5.8±0.92az

5.8±0.92az

6 - - 5.4±0.52az

5.7±1.06az

5.7±0.67az

COLOUR

1 5.9±0.74ay

6.9±0.32az

6.9±0.32az

6.7±0.82az

6.8±0.92az

2 5.3±0.82ay

6.8±0.42abz

6.5±0.53abz

6.3±0.48az

6.4±0.70abz

3 5.2±0.63ay

6.7±0.48abz

6.5±0.71abz

6.2±1.23az

6.3±0.82abz

4 - 6.2±0.92bz

6.0±0.82bz

5.7±0.82az

5.8±0.92abz

5 - 5.4±0.84cz

5.8±1.23bz

5.6±1.43az

5.6±1.58bz

6 - - 5.7±0.94bz

5.6±1.42az

5.6±1.58bz

a,b,cValues in the same column with the same letter are not significantly different (p>0.05); y,zValues in

the same row with the same letter are not significantly different (p>0.05). – discarded samples. LDPE:

Low Density Polyethylene, PP: Polypropylene, LDPE/PP: Coextruded Low Density

Polyethylene/Polypropylene. Juiciness, tenderness, flavours intensity. Sensory measurements using 8

point scale: 8 = Extremely juicy, tender, intense, bright; 1= Extremely dry, tough, bland, dark

70

CHAPTER FIVE

CONCLUSION AND RECOMMENDATIONS

5.1CONCLUSION

Based on the studies it was observed that unam inung packaged with coextruded LDPE/PP

was highly acceptable to the panelists and had a good physico-chemical properties showing

acceptable total viable counts, thiobarbituric acid reactive substances and free fatty acids at 6

months of storage. Being a popular meat product indigenous to the South-South geographical

zone of Nigeria, the product has a great market potential. However, the study has revealed that

unam inung cannot be stored in clay pot (as practiced traditionally) for a prolonged period,

beyond 5 months, since incipient spoilage is inevitable from the 5th

month of storage at ambient

conditions. Nevertheless, since clay pot packaging can only serve to hold the products

temporarily. The above notwithstanding, with increasing urbanization, there is no guarantee that

this product would not be held by distributors beyond 4 months in marketing channel or even at

homes. On this realization/possibility, it is best to use the PP/LDPE co-extruded plastic film for

its packaging.

5.2 RECOMMENDATIONS

Research on the synergy of using local clay in form of nonaclay in the co-extrusion of the

films should be investigated.

Effect of different co-extruded films thickness should be verified on the unam inung

packaging.

71

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78

APPENDICES

APPENDIX I

QUESTIONNAIRE

Department of Food Science and Technology,

University of Nigeria, Nsukka.

Score Card for Sensory Evaluation of Unam Inung

Directions

Please take these samples one by one and evaluate them for the following parameters on

hedonic scale as given at the end of form. Each characteristic has an 8 point rating scale for

judgement according to the degree of magnitude. It is very important to rinse mouth thoroughly

with clean water after evaluation of each sample. Note: tick () in the appropriate cell in the

table below.

Name of the Judge -----------------------------------

Sex -----------------------------------

Date ---------------------------

CHARACTERISTIC ONE: JUICINESS

Quality Treatment Samples

Description score 101 111 121 131 141

Extremely Juicy 8

Very Juicy 7

Moderately Juicy 6

Slightly Juicy 5

Slightly Dry 4

Moderately Dry 3

Very Dry 2

Extremely Dry 1

79

CHARACTERISTIC TWO: TENDERNESS

Quality Treatment Samples

Description score 101 111 121 131 141

Extremely Tender 8

Very Tender 7

Moderately Tender 6

Slightly Tender 5

Slightly Tough 4

Moderately Tough 3

Very Tough 2

Extremely Tough 1

CHARACTERISTIC THREE: FLAVOUR INTENSITY

Quality Treatment Samples

Description score 101 111 121 131 141

Extremely Intense 8

Very Intense 7

Moderately Intense 6

Slightly Intense 5

Slightly Bland 4

Moderately Bland 3

Very Bland 2

Extremely Bland 1

80

CHARACTERISTIC FOUR: COLOUR

Quality Treatment Samples

Description score 101 111 121 131 141

Extremely Bright 8

Very Bright 7

Moderately Bright 6

Slightly Bright 5

Slightly Dark 4

Moderately Dark 3

Very Dark 2

Extremely Dark 1

81

APPENDIX II

Table A: Average of moisture content (%) for unam inung stored with different packaging

materials at room temperature for six months

a,b,c, Values in the same column with the same letter are not significantly different (p>0.05); w,x,y,z Values in the same

row with the same letter are not significantly different (p>0.05).

Table B: Average of crude protein content (%) for unam inung stored with different packaging

materials at room temperature for six months

Time Samples

(month) unpackaged Clay pot LDPE PP LDPE/PP

1 28.39±0.43ez

29.42±0.43dyz

31.31±0.21cw

33.82±0.09ay

32.59±0.06bw

2 28.83±0.24ez

29.94±0.06dz

33.87±0.13cz

35.43±0.03az

34.73±0.07bz

3 23.05±1.05cy

29.24±0.07by

32.77±0.13ax

33.82±0.09ay

33.91±0.12ay

4 23.26±0.12cx

33.33±0.01ay

32.43±0.18bx

33.34±0.20ax

5 23.14±0.01cx

26.59±0.24bu

26.22±0.06bv

29.10±0.13au

6 28.72±0.07bv

27.56±0.18cw

29.68±0.06av

a,b,c,d,e Values in the same column with the same letter are not significantly different (p>0.05); u,v,w,x,y,z Values in the

same row with the same letter are not significantly different (p>0.05).

Time Samples

(month) unpackaged Clay pot LDPE PP LDPE/PP

1 29.54±0.31ay

28.39±0.55ay

26.73±0.39bx

24.78±0.31cy

25.94±0.62bcxy

2 29.21±0.70ay

27.87±0.16ay

25.01±0.71bw

23.95±0.64by

24.40±0.42bx

3 36.14±1.65az

28.63±0.32by

25.91±0.83bcxw

25.57±1.51cy

24.90±0.42cx

4 36.14±0.70az

25.23±0.38bw

26.07±0.72by

25.36±0.68bx

5 35.96±0.00az

31.76±0.11bz

32.84±1.63abz

30.18±2.38bz

6 29.21±0.20ay

31.83±2.37az

28.39±0.55ayz

82

Table C: Average of crude fat content (%) for unam inung stored with different packaging

materials at room temperature for six months

Time Samples

(month) unpackaged Clay pot LDPE PP LDPE/PP

1 13.93±0.11abz 14.08±0.04

az 13.63±0.25bz 13.98±0.04

abz 13.93±0.11abz

2 12.73±0.11cy 13.98±0.04

ayz 12.95±0.07cy 13.38±0.11

by 13.48±0.11by

3 12.03±0.04dx

13.83±0.11axyz 12.38±0.11

cx 12.98±0.04bx 13.03±0.04

bx

4 13.75±0.14axy 12.03±0.04

cw 12.90±0.07bx 12.98±0.04

bx

5 13.68±0.11ax 11.88±0.04

cvw 12.67±0.02bw 12.78±0.04

bw

6 11.68±0.04cv 12.28±0.04

bv 12.53±0.11av

a,b,c,d, Values in the same column with the same letter are not significantly different (p>0.05); v,w,x,y,z Values in the

same row with the same letter are not significantly different (p>0.05).

Table D: Average of aw values for unam inung stored with different packaging materials at room

temperature for six months

a,b,c,d Values in the same column with the same letter are not significantly different (p>0.05); v,w,x,y,z Values in the

same row with the same letter are not significantly different (p>0.05).

Time Samples

(month) unpackaged Clay pot LDPE PP LDPE/PP

1 0.91±0.01ay 0.87±0.00

bv 0.87±0.00by 0.87±0.00

byz 0.87±0.00bz

2 0.88±0.00bx 0.89±0.00

aw 0.88±0.01by 0.85±0.00

dx 0.86±0.00cz

3 0.93±0.01az 0.91±0.00

by 0.86±0.00cx 0.86±0.00

cxy 0.86±0.00cz

4 0.90±0.00ax 0.85±0.00

bw 0.83±0.00cw 0.84±0.01

cy

5 0.94±0.01az 0.91±0.01

bz 0.88±0.01cz 0.87±0.00

cz

6 0.88±0.00ay 0.87±0.01

byz 0.86±0.01bz

83

Table E: Average of pH values for unam inung stored with different packaging materials at room

temperature for six months

a,b,c,d,e Values in the same column with the same letter are not significantly different (p>0.05); x,y,z Values in the same

row with the same letter are not significantly different (p>0.05).

Table F: Average of NaCl values for unam inung stored with different packaging materials at

room temperature for six months

a,b,c, Values in the same column with the same letter are not significantly different (p>0.05); w,x,y,z Values in the same

row with the same letter are not significantly different (p>0.05).

Time Samples

(month) unpackaged Clay pot LDPE PP LDPE/PP

1 6.35±0.07az 6.30±0.00

ax 6.10±0.00bx 6.10±0.00

bz 6.10±0.00byz

2 6.45±0.07az

6.30±0.00bx 6.20±0.00

cy 6.10±0.00dz 6.00±0.00

ey

3 6.50±0.00az 6.35±0.07

bxy 6.25±0.07bcyz 6.20±0.00

cz 6.15±0.07cz

4 6.45±0.07ay 6.10±0.00

bx 6.15±0.07bz 6.20±0.00

bz

5 6.80±0.00az 6.30±0.00

bz 6.15±0.07cz 6.15±0.07

cz

6 6.10±0.00ax 5.95±0.07

by 6.10±0.00ayz

Time Samples

(month) unpackaged Clay pot LDPE PP LDPE/PP

1 8.41±0.09cz 8.75±0.16

cz 9.29±0.13by 10.02±0.12

az 9.57±0.23bz

2 8.50±0.20bz

8.91±0.06bz 9.93±0.28

az 10.37±0.28az 10.18±0.18

az

3 6.88±0.04cy 8.68±0.09

bz 9.59±0.01ayz 9.73±0.30

az 9.97±0.17az

4 6.91 ±0.13by 9.84±0.15

az 9.53±0.15az 9.80±0.26

az

5 6.92±0.08by 7.87±0.03

abw 7.58±0.04aby 8.25±0.27

ay

6 8.50±0.06ax 7.82±0.06

ay 8.75±0.16ay

84

Table G: Average of soluble protein values for unam inung stored with different packaging

materials at room temperature for six months

a,b,c,d,e, Values in the same column with the same letter are not significantly different (p>0.05); w,x,y,z Values in the

same row with the same letter are not significantly different (p>0.05).

Table H: Average of TBARS values for unam inung stored with different packaging materials at

room temperature for six months

a,b,c,Values in the same column with the same letter are not significantly different (p>0.05); v,w,x,y,z Values in the same

row with the same letter are not significantly different (p>0.05).

Time Samples

(month) unpackaged Clay pot LDPE PP LDPE/PP

1 39.72±0.10ay

39.49±0.06aw

38.55±0.19cw

38.81±0.04by

38.52±0.08cy

2 39.87±0.01ay

39.53±0.01bw

39.11±0.04cy

38.89±0.07dy

38.36±0.07ey

3 41.91±0.12az

39.90±0.04bx

39.30±0.06cyz

39.20±0.04cdz

39.10±0.03dz

4 40.81±0.07ay

39.47±0.06bz

39.34±0.01bz

39.24±0.13bz

5 41.09±0.13az

39.16±0.10by

39.28±0.08bz

39.12±0.02bz

6 38.85±0.10ax

38.51±0.07bx

38.42±0.01by

Time Samples

(month) unpackaged Clay pot LDPE PP LDPE/PP

1 1.66±0.03ax 1.11±0.15

bw 0.84±0.06cv

0.74±0.07cv

0.77±0.02cw

2 1.92±0.08ay 1.80±0.11

ax 1.20±0.24bw 1.07±0.11

bw 1.23±0.05bwx

3 2.25±0.11az 1.99±0.01

ax 2.07±0.16ax 1.37±0.05

bx 1.50±0.26bxy

4 2.56±0.15ay 2.34±0.11

ax 1.94±0.06by 1.79±0.01

by

5 3.10±0.12az 3.26±0.07

ay 2.12±0.18by 1.85±0.02

by

6 4.67±0.13az 3.55±0.06

bz 2.57±0.44cz

85

Table I: Average of FFA values for unam inung stored with different packaging materials at room

temperature for six months

a,b,c,Values in the same column with the same letter are not significantly different (p>0.05); v,w,x,y,z Values in the same

row with the same letter are not significantly different (p>0.05).

Table J: Average of vitamin E values for unam inung stored with different packaging materials at

room temperature for six months

a,b,Values in the same column with the same letter are not significantly different (p>0.05); x,y,z Values in the same

row with the same letter are not significantly different (p>0.05).

Time Samples

(month) unpackaged Clay pot LDPE PP LDPE/PP

1 0.29±0.01ay 0.27±0.00

bv 0.27±0.01bw

0.26±0.00bv

0.25±0.01cv

2 0.38±0.03ay 0.35±0.01

abw 0.32±0.02bcwx 0.29±0.01

cv 0.31±0.01bcw

3 0.75±0.11az 0.40±0.01

bx 0.35±0.03bxy 0.34±0.01

bw 0.33±0.00bwx

4 0.52±0.02ay 0.39±0.02

by 0.40±0.00bx 0.37±0.01

bx

5 0.70±0.03az 0.45±0.03

cz 0.55±0.04by 0.54±0.01

by

6 0.50±0.00bz 0.67±0.04

az 0.64±0.05az

Time Samples

(month) unpackaged Clay pot LDPE PP LDPE/PP

1 0.217±0.00bz 0.226±0.00az

0.223±0.00abz

0.223±0.00abz

0.223±0.00abz

2 0.203±0.00by 0.225±0.01az 0.221±0.00ayz 0.222±0.00az 0.221±0.00az

3 0.187±0.00bx 0.218±0.00ayz 0.217±0.00ayz 0.217±0.00ayz 0.216±0.00ayz

4 0.214±0.01axy 0.210±0.01bxy 0.214±0.01axyz 0.213±0.00abxyz

5 0.206±0.01ax 0.204±0.01ax 0.207±0.01axy 0.207±0.01axy

6 0.199±0.01ax 0.205±0.01ax 0.204±0.01ax

86

Table K: Average vitamin C values for unam inung stored with different packaging materials at

room temperature for six months

a,b,c,Values in the same column with the same letter are not significantly different (p>0.05); v,w,x,y,z Values in the same

row with the same letter are not significantly different (p>0.05).

Table L: Average vitamin A values for unam inung stored with different packaging materials at

room temperature for six months

a,b,c,d,Values in the same column with the same letter are not significantly different (p>0.05); u,v,w,x,y,z Values in the

same row with the same letter are not significantly different (p>0.05).

Time Samples

(month) unpackaged Clay pot LDPE PP LDPE/PP

1 13.50±0.05cz

14.55±0.13az

13.46±0.33cz

14.30±0.13abz

13.89±0.16bcz

2 12.29±0.10cy

14.45±0.33az

12.21±0.66cyz

13.90±0.26abyz

13.07±0.33bcyz

3 11.09±0.15cx

14.25±0.39az

10.97±0.10cxyz

13.50±0.39abxyz

12.25±0.48bcxy

4 14.09±0.52az

9.72±1.33cwxy

13.09±0.52abxyz

11.44±0.64bcwx

5 13.94±0.64az

8.48±1.66cwx

12.69±0.65abxy

10.62±0.81bcvw

6 7.23±1.99bw

12.29±0.78ax

9.81±0.97abv

Time Samples

(month) unpackaged Clay pot LDPE PP LDPE/PP

1 7.01±0.01bz

7.13±0.03az

7.02±0.03bz

7.04±0.11bz

7.04±0.03bz

2 5.40±0.01cy

5.60±0.03ay

5.40±0.03cy

5.50±0.01by

5.47±0.03by

3 4.79±0.01cx

5.05±0.03ax

4.78±0.03cx

4.96±0.01bx

4.91±0.03bx

4 4.11±0.03aw

3.76±0.03cw

4.02±0.01bw

3.95±0.03bw

5 2.97±0.03av

2.54±0.03dv

2.88±0.01bv

2.78±0.03cv

6 1.92±0.03cu

2.26±0.01au

2.16±0.03bu

87

Table M: Average TVC counts for unam inung stored with different packaging materials at room

temperature for six months

a,b,c,d,e,Values in the same column with the same letter are not significantly different (p>0.05); v,w,x,y,z Values in the

same row with the same letter are not significantly different (p>0.05).

Table N: Average mould counts for unam inung stored with different packaging materials at

room temperature for six months

a,b,c,d,Values in the same column with the same letter are not significantly different (p>0.05); w,x,y,z Values in the same

row with the same letter are not significantly different (p>0.05).

Time Samples

(Month) Unpackaged Clay Pot LDPE PP LDPE/PP

1 8.3x105±0.07

ax 4.2x10

5±0.14

dw

5.05x10

5±0.0

bz

4.6x10

5±0.0

cz

3.85x10

5±0.0

ez

2 9.0x105±0.07

axy 6.5x10

5±0.14

bx 4.35x10

5±0.0

cy 3.98x10

5±0.0

cy 3.0x10

5±0.0

dy

3 9.55x105±0.00

ay 6.78x10

5±0.11

bx 4.30x10

5±0.0

cy 2.94x10

5±0.00

dx 2.03x10

5±0.0

ex

4 1.35x106±0.07

az 8.28x10

5±0.80

by 4.25x10

5±0.6

cy 1.98x10

5±0.70

dw 1.48x10

5±0.7

dw

5 9.2x105±0.00

ay 4.2x10

5±0.0

by 1.87x10

5±0.00

cw 1.08x10

5±0.0

dv

6 1.20x106±0.14

az 4.2x10

5±0.0

by 1.53x10

5±0.00

cw 1.0x10

5±0.0

cv

Time Samples

(month) unpackaged Clay pot LDPE PP LDPE/PP

1 4.0x10±0.07bw 3.0x10±0.0cz 5.5x10±0.0az 1.0x10±0.0ez 2.0x10±0.0dz

2 1.61x102±0.07ax 2.45x10±0.0bcy

3.5x10±0.0by

5.0x10-0±0.7cz

1.5x10±0.0bcy

3 2.75x102±0.00 ay 1.5x10±0.0bx 2.0x10±0.00bx 0.0x10-0±0.0bz 0.0x10-0±0.0by

4 4.25x102±0.07az 1.0x10±0.7bw 1.0x10±0.7bwx 0.0x10-0±0.0bz 0.0x10-0±0.0by

5 1.0x10±0.7aw 5.0x10-0±0.7aw 0.0x10-0±0.0az 0.0x10-0±0.0ay

6 1.0x10±0.7aw 5.0x10-0±0.7aw 0.0x10-0±0.0az 0.0x10-0±0.0ay