a review on tomato authenticity quality control methods in conjunction with multivariate analysis...

5/20/2018 A Review on Tomato Authenticity Quality Control Methods in Conjunction With Multivariate Analysis (Chemometrics)

1/36

_______________________________________________________________

_______________________________________________________________

Report Information from ProQuest

May 14 2014 03:05

Created by My Research account: LUCIANCUIBUS (Lucian Cuibus)

_______________________________________________________________

14 May 2014 ProQuest


2/36

able of contents

1. A Review on Tomato Authenticity: Quality Control Methods in Conjunction with Multivariate Analysis

(Chemometrics)............................................................................................................................................... 1

14 May 2014 ii ProQuest


3/36

Document 1 of 1

A Review on Tomato Authenticity: Quality Control Methods in Conjunction with Multivariate Analysis

Chemometrics)

Author:Arvanitoyannis, Ioannis S; Vaitsi, Olga B

ProQuest document link

Abstract:

Authenticity and traceability have been two of the most important issues in the food chain. Authenticity

in particular, is closely related with both food quality and safety issues. Vegetables stand for a category of foods

heavily affected by adulteration either in terms of geographic origin (national or international level) or production

methods (organic or conventional production, fertilizers, pesticides, genetically modified vegetables). This

review aims at addressing most of the currently applied methods for ensuring quality control of vegetables; a)

instrumental: ion chromatography, high pressure liquid chromatography, atomic absorption spectrophotometry,

electronic nose and mass spectroscopy and b) sensory analysis. The results of all the above mentioned

methods were analyzed by means of multivariate analysis (principal component analysis, discriminant analysis,

cluster analysis, canonical analysis, and factor analysis). All ensuing results and conclusions are summarized in

eight comprehensive tables. [PUBLICATION ABSTRACT]

Full text: Headnote

Authenticity and traceability have been two of the most important issues in the food chain. Authenticity in

particular, is closely related with both food quality and safety issues. Vegetables stand for a category of foods

heavily affected by adulteration either in terms of geographic origin (national or international level) or production

methods (organic or conventional production, fertilizers, pesticides, genetically modified vegetables). This

review aims at addressing most of the currently applied methods for ensuring quality control of vegetables; a)

instrumental: ion chromatography, high pressure liquid chromatography, atomic absorption spectrophotometry,

electronic nose and mass spectroscopy and b) sensory analysis. The results of all the above mentioned

methods were analyzed by means of multivariate analysis (principal component analysis, discriminant analysis,

cluster analysis, canonical analysis, and factor analysis). All ensuing results and conclusions are summarized in

eight comprehensive tables.

Keywords tomato, authenticity, adulteration, quality control, chemometrics, multivariate analysis, genetically

modified tomato

INTRODUCTION

The adulteration of foods and beverages has been a problem ever since man stopped producing his own food

and had to rely on commercial supplies. The driving force behind any adulteration is the substitution of an

expensive component with a lower cost ingredient(s), hopefully without the consumer being able to perceive the

extension/substitution, in order to make additional gain (Hammond, 1996).

Fruits and vegetables form an essential component of the daily diet and have been mainly responsible for

contributing a variety of tastes and flavors, for widening the recipe range and attractiveness (Singhal et al.,

1997). In general, authenticity issues fall into at least one of the following categories (Ulberth, 2003):

* Non-compliance with legal requirements (product standards; geographical origin of the product, max/min water

content)

* Erroneous addition of certain ingredients

* Non-compliance regarding the use of certain technological processes

Species identification is effectively carried out with a number of analytical methods; electrophoretic techniques[Polyacrylamide gel electrophoresis, isoelectric focusing (IEF), sodium dodecyl sulphate Polyacrylamide gel

electrophoresis (SDSPAGE)], antibody techniques (immunodiffusion and immunoelectrophoretic methods),

DNA techniques, and chromatographic techniques [hybridization based methods, polymerase chain reaction

14 May 2014 Page 1 of 34 ProQuest
http://search.proquest.com/docview/199134781?accountid=31721http://search.proquest.com/docview/199134781?accountid=31721


4/36

(PCR), PCR-RFLP (restriction fragment length polymorphism)] and sequence analysis (Lees and Popping,

2003).

The EU Commission defines traceability as: "the possibility to find and follow the trace, throughout all the stages

of production, processing and distribution of a foodstuff, feedstuff, an animal destined for food production or a

substance destined to be incorporated in foodstuff or feedstuff or with a probability of being used as such"

(REGULATIONS (EC) No 1830/2003 &882/2004).Over the last decade multivariate data analysis techniques have seen wider acceptance and use in almost all

fields of scientific inquiry. Although many reasons can be advocated, the following two stand for the most

important ones:

* The realization that in many scientific inquiries it is necessary to analyze the simultaneous relationships

among three or more variables

* The advent of the high speed computer with large storage facility and the development of readily available and

easy to use software packages for implementing multivariate analysis (Dillon and Goldstein, 1984).

MVA includes all statistical methods that simultaneously analyze multiple measurements on each individual or

object under investigation. Since MVA is defined as simultaneous analysis of more than two variables, many

multivariate techniques are extensions of univariate analysis and bivariate analysis i.e. simple regression is

extended to the multivariate case to include several predictor variables. A confusion issue for the definition of

MVA resides in its inconsistent use either for examining relationships between or among more than two

variables or only for problems in which all the multiple variables are assumed to have a multivariate normal

distribution (Hair et al., 1998).

Most commonly multivariate statistics are applied for (http://

trochim.human.cornell.edu/tutorial/flynn/multivar.htm):

* Developing taxonomies or systems of classification

* Investigating promising approaches to conceptualize or group items

* To generate hypotheses

* To test hypotheses

Multivariate analytical techniques/chemornetrics are widely applied in industry, government, and university-

related centers (Hair et al., 1998). Multivariate analysis methods are anticipated to predominate in the future

and result in substantial changes in the manner in which researchers think about problems and design their

research (Tatsuoka and Tiedeman, 1963).

The aim of this review is

a) to present some of the most commonly and effectively used analysis methods (physicochemical,

immunoassay, sensory) for tomato authentication (cultivar, geographical origin, genetically modified) and

b) to summarize all research findings in the above mentioned topics in conjunction with the implementation ofmultivariate analysis.

QUALITY CONTROL

Authentication of food products is of primary importance for both consumers and industries. From the legislative

point of view, quality standards were established through the requirement of quality labels that specify the

chemical composition of each product. From the economic point of view, product authentication is essential to

avoid unfair competition that can eventually create a destabilized market and disrupt the regional economy and

even the national economy (Cordella et al., 2002). Product labeling (identity of product) is one of the issues

helping the consumer and the authorities to undertake legal action, because an infringement of the label could

result in a criminal charge in the court of justice. However, a series of analyses have to be carried out (with

specific analytical techniques as prescribed by IDF, AOAC) in order to make sure that this specific product is,

indeed, adulterated or altered (Arvanitoyannis et al., 2005).

Physico-Chemical Methods



5/36

There is increasing consumer demand for fresh-cut fruits and vegetables, as a source of vitamins and

antioxidants. However, controls during fresh-cut processing are essential, because antioxidants such as

phenolics and AA (Ascorbic Acid) are affected when bruising, trimming, and cutting of fruits and vegetables

occurs. Therefore, research should focus on the optimal maintenance of both nutritional and sensorial qualities

of freshcut products (Tudela et al., 2003). Howevers, a simultaneous analysis of different minerals in food or

biological samples is a frequent request not only to prove their quality but also to identify their origin. At thepresent time the most common methods for mineral analyses are atomic absorption spectroscopy (AAS),

inductively coupled plasma mass spectroscopy (ICP-MS), and Ion Chromatography (Fredrikson et al., 2002).

Ion Chromatography

Ion chromatography (IC) is an analytical technique for the separation of ion solutes in water in general,

especially environmental, in industrial processes, the metal industry, and industrial waste water in biological

systems in pharmaceutical samples in food etc. IC can be classified as a liquid chromatography method, in

which a liquid permeates through a porous solid stationary phase and elutes into a flow-through detector. The

stationary phase is usually in the form of a small-diameter (5-10 mm) uniform particles, packed into a cylindrical

column. The column is constructed from a rigid material (such as stainless steel or plastic) and is generally 5-30

cm long and the internal diameter is in the range of 4-9 mm. A high pressure pump is required to force the

mobile phase through the column at typical flow rates of 1-2 ml/min. The sample to be separated is introduced

into the mobile phase with an injection device, manually or automatically, prior to the column. A typical

chromatographic system is shown in Fig. 1 (http://www.forumsci.co.il/HPLC/ion.chrm.html.

Any chromatographic system of the type shown in Fig. 1 can be divided into instrumentation and chemistry

components. The instrumentation components are the pump, injector, detector, and the data station, whereas

the chemical components are the mobile and the stationary phases. Such instrumentation is typical to high

performance liquid chromatography (HPLC). The chemistry components determine that this mode of HPLC is

dedicated to the analysis of ions. In any chromatographic mode the composition of the mobile phase provides

the chemical environment for the interaction of the solutes with the stationary phase. Separation can be

achieved by controlling and manipulating these interactions, greatly affecting the relative retention times of the

various sample components. The types of solutes determined with IC techniques are the following:

i) Inorganic ions such as Cl-, Br-, SO^sup 2-^^sub 4^ etc.

ii) Inorganic cations, including alkali metal, alkaline earth, transition metal, and rareearth ions, but not neutral

metal complexes,

iii) Organic acids, including carboxylic, sulfonic, phosphonic acids etc.,

iv) Ionic organo-metallic compounds.

The liquid chromatographic techniques applicable to the above-described separations are termed as follows:

i) Ion-exchange chromatography,



6/36

ii) Ion-exclusion chromatography,

iii) Ion-pair (Ion-interaction) chromatography,

iv) Capillary electrophoresis.

Separation Mechanisms in HPLC

A useful classification of the various LC techniques is based on the type of distribution (or equilibrium)

responsible for separation. Common interaction mechanisms encountered in LC are classified as adsorption,partition, ion-exchange, gel permeation or size exclusion, and chiral interaction. In practice, most LC

separations are the result of mixed mechanisms (http://www. labaluance.com/la_info/support/hplc3.htm).

Absorption. When the stationary phase in HPLC is a solid, the type of equilibrium between this phase and the

liquid phase is termed "absorption." All of the pioneering work in chromatography was based upon absorption

methods, in which the stationary phase is a finely divided polar solid that contains surface sites for retention of

analysis. The composition of the mobile phase is the main variable that affects the partitioning of analytes. Silica

and alumina are the only stationary phases used, the former being preferred in most applications. Applications

of absorption chromatography include the separation of relatively non-polar water-insoluble organic compounds

and the separation of isomers in a mixture where subtle variations in the mobile phase occur (Fredrikson et al.,

2002).

Partition. The equilibrium between the mobile phase and the stationary phase comprising of either a liquid

absorbed on a solid or an organic species bonded to a solid is described as a "partition." Bonded stationary

phases are prepared by reaction of organochlorosilane with the reactive hydroxyl groups on silica. When the

stationary phase is polar and the mobile phase relatively less polar (n-hexane, ethyl ether, chloroform), this type

of chromatography is referred to as "normal-phase chromatography." When the mobile phase is more polar thanthe stationary phase, this type of chromatography is called "reversed-phase chromatography." Because of its

versatility and wide range of applicability, reversed-phased chromatography, using a polar aqueous-based

mobile phase mixture containing an organic polar solvent such as methanol or acetonitrile, is the most

frequently used HPLC method (Table 1). Applications include non-ionic compounds, polar compounds, and

certain cases ionic compounds. (http://www.laballiance.com/laJnfo/support/hplc3.htm)

Atomic Absorption Spectrophotometry

Measurements of the amount of light absorbed at resonant wavelength stand for a quantitative determination of

the amount of analyte element present (Fig. 2). The use of special light sources and careful selection of

wavelength allow the specific quantitative determination of individual element in the presence of others. The

atom cloud required atomic adsorption measurements is produced by supplying enough thermal energy to the

sample to dissociate the chemical compounds into free atoms. Under the proper flame conditions, most of the

atoms remain in the ground state form and are capable of absorbing light at the analytical wavelength from a



7/36

source lamp. Precise and accurate determinations can be made with this technique, thereby establishing atomic

adsorption as one of the most popular methods for the determination of metals (Beaty and Kerber, 1993).

Barba et al. (2006), optimized an HPLC method for the determination of lycopene and b-carotene in vegetables

and compared it with a spectrophotometric standard method. Among the different conditions studied the most

suitable ones for the samples were: extraction with hexane/acetone/ethanol (2:1:1 v/v/v), evaporation ofthe

hexane layer, dissolution ofthe dry extract in THF/ACN/ methanol (15:30:55 v/v/v), and injection on a C18

column with methanol/ACN (90:10 v/v)+TEA 9IM as mobile phase (U = 0.9 ml/min) and M^sub detection^ = 475

nm. Samples employed for analysis were tomato, carrot, pepper, watermelon, persimmon, and medlar. The

HPLC method proposed showed adequate reproducibility (RSD


8/36

computer equipment. Sensory data treatment was carried out with computer program CASA (Computer Aided

Sensory Analysis) (Auerswald et al., 1999).

Johanson et al. (1999) used a selected group of seven assessors (n = 7) trained to carry out a descriptive test

and conventional profiling, on tomatoes. The assessors developed a list of profiling attributes and agreed on the

following attributes: for consistency firm and juicy and for taste tomato taste intensity, sweet, bitter, and

acidulous (ISO, 1992) taste. Prior to profiling the tomatoes, these assessors were trained to identify, e.g. tomatotaste intensity at different levels by being presented with tomatoes at different stages of ripeness.

Sensory analysis was performed with a panel of 54 trained panelists. Judges were grouped into four panels

(Causse et al., 2001). Three composed of seed company employees (Clause, Vilmorin, Tezier), with 20, 8, and

8 panelists, respectively. The fourth panel (Dijon) composed of 18 volunteers already trained for sensory

analysis with other products. This panel performed three assays per week, while the other three performed only

one. Panelists were trained during 13 assays before the experiment began. Attributes were selected after two

years of sensory analysis with tomato material. The aim of a work carried out by Le and Ledauphin (2006) was

to provide answers to the questions:

A) Were there segments of consumers differing in their liking of the tomato varieties? and

B) How could the preferences of these segments be explained in terms of the sensory and physico-chemical

attributes of the tomatoes, or the demographic, usage, and attitudinal characteristics of the consumers?

First, a multiple factor analysis (MFA) was performed on the table that describes the tomatoes, considering on

the one hand the sensory attributes, and on the other hand the physicochemical attributes; we then obtained a

map of the tomatoes on the basis of their description, where the contribution from both groups of data is

balanced. Then, we performed a hierarchical cluster analysis (HCA) of the consumers on the basis of the

correlation coefficients between their preferences and the coordinates of the tomatoes provided by MFA. This

analysis led to three segments of consumers that differ in their liking of the tomato varieties. Those segments

represent, respectively, 39.8%, 39.6%, and 20.6% of the population. The first two segments are rather similar

regardless to the firmness of the varieties since they both like sweet and flavourful tomatoes. Consumers of the

third segment do not seem to be very fond of tomatoes according to their cooking uses and habits (Le and

Ledauphin, 2006).

Consumer Preference Test

Another method of sensory analysis of tomato varieties or other vegetables is the consumer preference test.

Every variety has a unique profile which the consumers know and trust in order to buy the specific product.

All consumers participating in the preference test (177) were divided into age groups as follows : 61 % were

between 31 and 60 years of age, 15 % between 20 and 30 years of age, 14% over 60 years of age, 8% under

20 years of age, and 2% did not answer the question. There were 61% females and 39% males of in all 177

consumers and 56% of them had post-graduate education. This was interpreted as standing for a typicalconsumer group for Sweden (Johanson et al., 1999).

Another consumer acceptance test used 100 housewives for product evaluation. They assessed products for

first impression, appearance, smell, flavor, aftertaste, and mouthfeel using unstructured scales with the anchor

points 0-"unpleasant/bad" and 100-"pleasant/good" (values of acceptance) (Auerswald et al., 1999).

Electronic Nose

The performance of electronic noses for the analysis of foods was tested by measuring sensor sensitivities to a

number of odoractive compounds of interest in food quality studies (Natale et al., 1997). These compounds are

representative of numerous classes of chemicals, such as organic acids, alcohols, amines, sulphides, and

carbonyls.

Since 1995, extensive research was carried out at the University of Rome on the exploitation of porphyrins and

related compounds for chemical sensors. Metalloporphyrins are basically assembled by four pyrrole rings linked

by methenyl groups to form a macrocycle. This basic structure can be modified by complexing a metal at the



9/36

center of the structure and/or linking some peripheral groups around the macrocycle. Recently,

metalloporphyrins were introduced as coating materials for quartz microbalances to obtain chemical sensors

(Brunink et al., 1996).The mean feature of such sensors is the dependence of sensing properties (in terms of

selectivity and sensitivity), on the nature of the central metal and on peripheral substituents, so that with only a

little variation in the synthesis process it is possible to get sensors with different sensitivity and selectivity

properties.

Figure 3 displays the measurements set up by means of the electronic nose. Samples were closed in bottles

from where headspaces were continuously transferred into the measurement chamber by means of a peristaltic

pump. The proper speed of the pump was opted for equilibrium in maintenance sample headspace. Dried

ambient air was used as carrier, and measurements were performed at room temperature. Reproducibility of

measurements was tested by measuring each sample from three to five times (Sinecio et al., 2000).

Storage Methods

Consumption of fresh-cut fruits and vegetables has increased as a response to the demand for quality and the

modern way of life of consumers. However, the shelf-life of minimally processed products is usually limited by

enzymatic browning, which causes a decrease in food quality because it implies spoilage. Therefore, the

prevention of this browning has been a challenge for food scientists. Minimal processing involves tissue injury

because of some mechanical processes (such as handling, peeling, and cutting). Such wounding induces many

physiological responses related to wound healing with a common secondary side reaction: browning

development (Cantos et al., 2002). The answer to storage problems is the continuous control of the storage

conditions. Nowadays, many storage conditions surveyed are in use at the market. However, there are some

standards for storage that are important for maintaining the quality of the products.

Freezing

Freezing is most likely the most common food storage technique employed nowadays. Freezing cancels the

natural decomposition process by delaying the chemical breakdown and killing the decomposer micro-

organism, thus preserving the food. Most produce requires blanching (heating vegetables in boiling water or

with steam, then submerging them in iced water for cooling) prior to freezing. Blanching helps color and

nutrients preservation in frozen vegetables and the blanching time is specific per type. Fruit darkening due to

freezing can be effectively prevented by dipping fruit in an antioxidant mixture (ascorbic acid) before freezing.

Frozen produce will generally last at least 12 months and oftentimes much longer. Airtight containers preventing

moisture loss and freezer burn are used in the tomato industry

http://wasatchgardens.org/Library/FoodStorage.PDF).Micra RS tomatoes, frozen in the form of cubes, were stored during 12 months at -20C and -30C, analyses

being conducted after freezing and after 3-, 6-, 9-, and 12-months' storage. Storage did not affect the level of

dry matter, soluble solids, sugars, dietary fiber, total nitrogen, nitrates, nitrites, pH, ash, or its alkalinity.



10/36

However, differences in contents of protopectins, pectins, total acidity, vitamin C, carotenoids, beta-carotene,

and lycopene and also in the activity of peroxidase, catalase, and lipase were statistically significant. In frozen

products at a temperature of -30C in comparison with those at -20C, the contents of the following were:

protopectins 33%, pectins 68%, vitamin C 90%, carotenoids 30%, beta-carotene 39%, and lycopene 43%, while

the activities of catalase and of lipase were 52% and 45% lower, respectively. Organoleptic ecaluation showed

good conservation quality in tomato cubes stored at -20C during 9 months and in the case of -30C, throughoutthe entire investigated period (Lisiewska and Kmiecik, 2000).

Dehydration

Similar to other preservation methods, dehydrating fruit, and vegetables slows down the chemical and micro-

biotic decomposition processes. Perhaps the oldest food preservation technique, dehydration, can be

accomplished using electric or solar powered dehydrators and ovens. Using electric dehydrators is the most

rapid method of drying vegetables and fruits, taking six or more hours before it is ready to be stored. Most

vegetables need to be blanched (above) before being dried and it is better to dip fruit in ascorbic acid syrup to

preserve color. Dehydrated food will store from 6 to 32 months depending on the type

(http://wasatchgardens.org/Library/FoodStorage.PDF.).

The overall material transfer (water and solubles) was measured during osmotic dehydration of onion slices and

tomato fruits in individual and mixed solutions of commercial salt and sugar. The dehydration phenomenon took

20 h in tomato fruits and 15 min in onion slices. The nature of the osmotic solution and the treatment time

affected the transfer process. A mixed solution of sugar and salt showed the highest dehydration capacity with

predominance of water removal and gain of solutes over solute loss. (Passo-Tsamo et al., 2005).

Cherry tomato samples were osmotically dehydrated in different hypertonic NaCl solutions (with or without

sucrose) at two different concentrations. Mass transfer kinetics was modelled according to the Peleg ( 1988),

the Fick ( 1975), and the Page (1949) equations. The Peleg equation resulted in the best fitting for water loss

and the Page model showed the best predictive capacity for salt gain data. The effective diffusivity determined

using Fick's second law applied to a spherical geometry was found to be in the range of 0.43 10^sup -9^-1.77

10^sup -9^ m^sup 2^/s for water loss and 0.04 10^sup -9^-0.54 10^sup -9^ m^sup 2^/s for salt gain.

Increased solution concentration resulted in higher water loss and salt gain. An addition of sucrose to osmotic

solutions decreased the driving force of the process (Azoubel and Xidieh-Murr, 2004).

Canning

Tomatoes, tomato sauces, salsas, peppers, peaches, and pears are the most commonly canned foods. Out of

all the food preservation techniques, canning requires the most equipment and stands for a most particular

process. Canning is carried out according to two main methods: water bath canning for high acidity foods (pH of

4.6 or lower) and pressure canning for low acidity foods. The difference is that for low acidity foods, a

temperature of 110C is required to kill any hazardous microorganisms. Both methods require large pots (or apressure caner for latter), canning jars, rings and lids, and jar lifter tongs. Canned food should be stored at 10-

21C in a dry and dark place (http://wasatchgardens.org/Library/FoodStorage.PDF.).

Modified Atmosphere Packaging (MAP)

Temperature control and modification of atmosphere are two important factors in the prolonging the shelf life of

fresh products. Modified atmosphere packaging (MAP) of fresh produce relies on the modification of the

atmosphere inside the package, achieved by the natural interplay between two processes, the respiration of the

product and the transfer of gases through the packaging, thus leading to an atmosphere richer in CO2 and

poorer in O2. This atmosphere can potentially reduce the respiration rate, the ethylene sensitivity and

production, and the decay and physiological changes, namely, oxidation (Gorris and Tauscher 1999; Saltveit,

1997). MA packages should be carefully designed, because, in the opposite case, the system may prove to be

ineffective or result in an even shorter shelf-life of the product. Design should take into consideration not only

steady-state conditions, but also the dynamic process, because if the product is exposed for a long time to



11/36

unsuitable gas condition before reaching the adequate atmosphere, the package may have no benefit. The

design of an MA package depends on a number of variables such as product properties, its mass,

recommended atmosphere composition, permeability ofthe packaging material to gases and its dependence on

temperature and the respiration rate of the product as affected by different gas composition and temperature.

Thus respiration rate modelling is central to die design of MAP for fresh fruits and vegetables (Fonseca et al.,

2001).Controlled Atmosphere (CA) Storage at Non-Optimum Temperature Conditions

One of the most effective means to maintain the quality of fresh fruits and vegetables is the maintenance of

temperature throughout the post-harvest handling chain. Although the use of CA storage does not replace the

benefits of an optimum storage temperature, it can in some cases alleviate the effects of non-optimum

temperatures. For example, when "Chandler" strawberries were stored in 5% O2 + 15% CO2 or 10% O2 + 20%

CO2 for up to two weeks at 4 or 10C to investigate the effects of CA at temperatures above the optimum for

strawberries, the results were, in fact, still beneficial (Nunes et al., 1995).

Storage of pink "Buffalo" tomatoes in 4% O2 + 2% CO2 at 12C contributed to shelf-life prolongation (Nunes et

al., 1996). However, the storage of these tomatoes under the same CA at 6C caused CO2 injury thus

accentuating the development of chilling injury symptoms such as water soaking, pitting, discoloration, and loss

of brightness. In contrast, Ratanachinakorn and his coworkers (1997) found that pink "Bermouda" tomatoes

were not injured when exposed to 0.5% O2 for one day or 80% CO2 for two days at 22C. It was apparent that

O2 and CO2 levels should be adjusted to maximize their beneficial effects on the quality characteristics of fruits

and vegetables depending on the anticipated temperature during postharvest handling.

Modified Atmosphere Packaging (MAP) at Varying Temperatures

A case of highly perishable products such as fresh-cut fruit or vegetables in MAP, which have a relatively short

shelf-life and are very vulnerable to temperature abuse, the maintenance of an adequate temperature near 0C

is obligatory to keep the product safe for consumption. Increases in temperature during shipping, handling or

retail display result in decreased O2 and increased CO2 levels inside the package due to a rise in the

respiration rate of the product.

Most MAP systems are designed for ensuring proper performance in a specific temperature, and films with

adequate O2 permeability, satisfactory response to temperature variations, or both are rare (Cameron et al.,

1995). Therefore, when the temperature increases, respiration tends to increase more than the package

permeation, thus creating fermentative conditions. Nevertheless, many MAP products are prepared, shipped,

and stored at temperatures between 5 and 10C (Vertinden and Nicolai, 2000) owing to the deficiencies of

environmental control often encountered during transportation. Cameron et al. (1995) reported that in MA-

package pre-cut salad greens purchased at the supermarket, the O2 levels determined inside the packages

were very low and ethanol accumulation was present in the majority of packages. In this case, the packageswere either not well-designed or subjected to higher temperatures than those for which they were initially

designed. Another problem associated with temperature variations during marketing of MAP products is the

development of high humidity inside the package, favoring condensation both on film and on package contents.

The presence of water may promote the development of decay and also block O2 diffusion into the tissue and

through the film, thus initiating fermentation (Cameron et al., 1995).

GMO Detection Methods

The authenticity of food and the methodology for testing are well-known topics in food science since many

years. Generally, all component characteristics for a specific food are suitable. Highly discriminating are

proteins and nucleic acids. For a long time nucleic acids present in food were not considered as an interesting

class of compounds in food chemistry, and indeed to recognize a relation between DNA and food quality is not

obvious. However, plant genetic engineering is rapidly proceeding and has led to numerous genetically modified

cultivars and many products are already on the market. DNA-analytical methods are the most promising way to



12/36

distinguish between genetically modified organisms (GMO) and non-GMO-products (Luthy, 1999).

GM crops are indistinguishable from non-GM crops to the naked eye. Testing methods therefore need to look

for the genes (DNA) "engineered" into the crop (DNA-Based Testing), or the proteins produced in the plant by

introduced DNA (Proteins-Based Testing). Each method is appropriate under certain conditions and it is

important to be aware of these when considering GMO testing (Arvanitoyannis, 2003, http://www.eurofins.

de/food-testing/food-analysis/gmo-test-identificationmethods/ eu#elisa).Genetically Modified Organisms (GMO)

A genetically modified organism (GMO) is a living organism, e.g. a plants whose genetic composition has been

altered by means of gene technology. The genetic modification usually involves insertion of a piece of DNA (the

insert), a synthetic combination of several smaller pieces of DNA, into the genome of the organism to be

modified. This process is called transformation. These smaller pieces of DNA are usually taken from other

naturally occurring organisms. In bacteria and probably in plants in the near future, genetic modifications can

also be introduced by altering existing codes without DNA insertion foreign.

A typical insert (gene construct) in a GMO composed of three elements:

1) Promoter element functions as an on/off switch for reading of the inserted/altered gene;

2) The gene inserted/altered is coded for a specific selected feature;

3) The terminator element functions as a stop signal for reading of the inserted/altered gene.

In addition, several other elements can be present in a gene construct, and their function is usually to control

and stabilize the function of the gene, demonstrate the presence of the construct in the GMO, or facilitate a

combination of the various elements of the construct. A gene construct must be integrated of the organism to

become stably inherited (Hoist-Jensen, 2001).

DNA Based Methods

DNA based methods look for specific genes, or DNA genetically engineered into the crop. Although, there is a

variety of DNA based methodologies, most commercial testing is currently conducted by means of the

Polymerase Chain Reaction (PCR) technology. PCR is used to target and amplify specific genes or sections of

DNA occurring in the GM crop, or a GM derived food product. Amplified DNA is determined with gel

electrophoresis. A positive result is indicated by a "band" on a gel, a negative result by no band. The real power

of PCR lies in its ability to detect trace amounts of GM DNA in complex mixtures of DNA, such as a processed

food sample. In principle, it can detect as low as a single copy of target DNA in a sample, representing a highly

sensitive means to detect GMOs (Hernandez et al., 2001). The main characteristics properties of DNA based

methods are summarized in Table 2.

Toward the development of reliable qualitative and quantitative Polymerase Chain Reaction (PCR) detection

methods of transgenic tomatoes, one tomato (Lycopersicon esculentum) species specific gene, LAT52, was

selected and validated as suitable for using as an endogenous reference gene in transgenic tomato PCR

detection. Both qualitative and quantitative PCR methods were assayed with 16 different tomato varieties, and



13/36

identical amplified products or fluorescent signals were obtained with all of them. No amplified products and

fluorescent signals were observed when DNA samples from 20 different plants such as soybean, maize,

rapeseed, rice, and Arabidopsis thaliana were used as templates. These results demonstrated that the amplified

LAT52DNA sequence was specific for tomato. Furthermore, the results of the Southern blot showed that the

LAT52 gene was a single-copy gene in the different tested tomato cultivars. In qualitative and quantitative PCR

analysis, the detection sensitivities were 0.05 and 0.005 ng for tomato genomic DNA, respectively. All of theseresults indicated that the LAT52 gene could be successfully used as a tomato endogenous reference gene in

practical qualitative and quantitative detection of transgenic tomatoes, even for some processed foods derived

from transgenic and nontransgenic tomatoes (Yang et al., 2005).

Multiplex PCR-Based Detection Methods

With multiplex PCR-based methods several target DNA sequences are screened for and detected in a single

reaction. Although, standard PCR methods may be combined in the same reaction this often results in an

unacceptably high risk of producing incorrect results from analyses of real samples. First, each method may

require different reaction conditions, e.g. different temperature regimes or different reagent concentrations.

second, the combination of primers from different methods may increase the risk of amplifying DNA fragments

other than the target fragments. Third, when more than one target fragment is being amplified in a PCR

reaction, the two fragments (amplicons) will compete for reagents etc. The development of multiplex assays

requires careful testing and validation. After the PCR the resulting pool of amplified DNA fragments needs to be

further analyzed to distinguish among various amplicons. This may be conducted by the use of specific

hybridization probes (possibly also during PCR in real-time assays), by gel electrophoresis and comparison of

fragments sizes. While several research groups are currently developing a number of multiplex assays, hitherto

only one article was published presenting a multiplex assay for detection of five GM-maize (Bt11, Bt176,

Mon810, T25 and GA21; Matsuoka et al., 2001).

Protein Based Methods

Proteins based methods use antibodies to detect or measure the amount of "novel" protein(s) produced by the

GMO. They may be divided into two principal types:

a) ELISA conducted in a laboratory, using antibodies to specifically detect GM proteins in a manner similar to

the way immune system detects foreign bodies. These antibodies are typically color coded to enable them to be

easily detected and quantified.

b) Strip tests; these tests can be carried out by personnel in the actual field. Typically, a sample for testing is

crushed and mixed with water. The strip is dipped into this mixture and the result monitored as the color of the

strip changes indicating whether or note the GMO variety is present (http://www. eurofins. de/food-testing/food-

analysis/gmotest-identification-methods/eu#elisa).

The advantages and disadvantages of protein based methods are summarized in Table 3.Multivariate Analysis/Chemometrics

Analytical chemistry today is a fast-growing and developing science. Strongly connected to analytical chemistry,

receiving impetus from it, and providing impetus back, chemometrics is also developing in a remarkable way.

Many analytical chemists apply chemometric principles and methods in their daily work, partly intentionally and

partly due to the software used in their equipment. The driving forces for the development of chemometrics

were on the one hand the fast development of powerful computers and convenient and easy-to-use software

packages, and on the other hand, analytical chemists that were using more efficient and productive analytical

equipment were (and still are) being faced with increasingly complex and complicated tasks. In particular, the

flood of data "produced" by modern multielement and multicomponent analytical apparatus requires the

application of chemometric methods in order to be able to pick the essential influencing factors from many

possible influences, to quantify their relationships, and to extract the latent information from immense amounts

of data (Einax, 2004).



14/36

Multivariate analytical techniques/chemometrics are widely applied in industry, government, and university-

related centers over the past thirty years (Hair et al., 1995). Multivariate analysis methods are anticipated to

predominate in the future and result in substantial changes in the manner in which researchers think about

problems and design their research. Principal component analysis (PCA) reduces the dimensionality of a data

set in which there is a large number of inter-correlated variables, while retaining as much as possible of the

information present in the original data. The reduction is achieved through a linear transformation to a new set

of uncorrected variables (PC scores) in which the first few ones will express most of the variation of the original

variables. Linear discriminant analysis (LDA) is usually applied to a subset of variables (Arvanitoyannis et al.,

2004). Principal component regression can be carried out on a dummy variable or variables that indicate class

membership. Partial least squares (PLS) models the relationship between the data sets using a series of local

least-squares fits.

Factor analysis transforms a n-dimensional data structure to another with considerably less dimensions, like

PCA, but gives the opportunity to the researcher to select between uncorrected factors. Correspondence factor

analysis has the advantage over the other techniques in that it relates the variables to those objects for which

they are particularly meaningful (Tzouros and Arvanitoyannis, 2001). Multidimensional scaling is a dimension-

reducing method that attempts to retain the distances among data points as well as possible. Clustering

techniques aim at grouping variables or objects in terms of their similarities/properties and are divided into

hierarchical and non-hierarchical groups. Procrustes analysis was first introduced as a method for matching two

configurations when two assessors (in the case of sensory evaluation) scored the same set of samples. The

analysis involves the mathematical operations of transformation to a common origin, rotation of axes, by which

one configuration is made to approach the other as nearly as possible (Arnold and Williams, 1998).



15/36

Current chemometrics research is directed toward tackling more difficult data problems. Feature selection, use

of neural networks, and pattern recognition methods and validating predictions conducted with soft modeling

methods are topics continuously gaining interest (Lavine, 1998). Chemometrics can be visualized as the

implementation of mathematical and statistical tools to the interpretation of patterns in multivariate data. They

are rapid and precise in analytical instrumental data. Table 4 summarizes all the abbreviations used and

provides their full names.

DISCUSSION

Instruments and methods that measure the performance of both quality traits and tomato characterization were

identified and evaluated on the basis of the defined criteria. The criteria for the performance tomato

characterization were four quality dimensions, i.e., physicochemical properties, sensory properties, storage

properties, and identification of genetic modified tomato.

Physicochemical Properties

Mohamed and his coworkers (2003) used certified absorption spectroscopic standard solutions (1mg/mL) of Ca,

Cd, Co, Cu, Fe, Mn, Ni, Pb, and Zn which were from BDH (UK). Standard solutions were prepared byappropriate dilutions of the stock solutions. Biological standards (Backer et al., 1974) (Bown's kale, orchard

leaves, and tomato leaves) and geological standards (Taskaev and Apostolov, 1982) (cool fly ash and granite II)

were used for cross-checking the results. A Perkin-Elmer HGA-3110 atomic absorption spectrophotometer

equipped with a Perkin-Elmer HGA-600 carbon furnace and autosampler As-60 was employed. Elements

hollow cathode lamps were used at recommended conditions; K and Na were measured with a JENWAY-PFP-7

flame photometer. A comparison of the minor element concentrations by a vegetable family, a new picture was

obtained. In the family Curcubitaceae, vegetable marrow exhibited higher concentrations of Ca, Cd, Co, Cu, Fe,

Mg, Mn, and Pd than did cucumber. In the family Salauaceae eggplant showed higher concentrations of Fe, K,

M, Pb, Mg, and Zn than potatoes, tomato, and green pepper (Mohamed et al., 2003).Betruzzi FT oil penetrometer (Facchina, Alfonsine, Italy) equipped with an 8 mm diameter punch was used by

Gmez and his coworkers (2001) to determine fruit firmness, expressed in kPa. Soluble solids were determined

by an Atago PR-100 digital reflactometer (Atago Co Ltd, Tokyo, Japan) the results being expressed in Brix.



16/36

The pH was measured directly in the filtered juice, after washing and triturating the fruit in a liquidizer, using a

micro-pH 2001 pH-meter (Crison Instruments SA, Alella, Barcelona, Spain). Citric and malic acids were

quantified using the filtered juice. Lycopene concentration was calculated by extraction in a hexane/acetone

mixture, the extracts being measured in a spectrophotometer at 501 nm. Fruit color was measured by means of

a Minolta CR-200 colorimeter (Minolta Camera Co Ltd, Osaka, Japan) at six points on each fruit in order to

obtain the CIELAB L*, a*, and b* parameters referring to the D65 illuminant and 2 angle vision. The smallestrange of variation in the chemical parameters studied was in the pH, and all varieties showed values equal to or

below 4.5 considered necessary for a satisfactory taste. The highest citric acid concentration (the predominant

acid in mature fruit) was determined in ESTIA2.

Voldich and his coworkers (2000) used various analytical markers including lycopene, b-carotene, 5-pyrrolidon-

2-carboxylic acid (pyroglutamic acid, PCA), glucose, fructose, sucrose, citric, and malic acid in an attempt to

determine the tomato content in ketchup. For PCA column used was: TESSEK, Separan SGX C-18, 10 m, 250

4 mm, with mobile phase: acetonitrile: chlorolform 85:15(v/v), flow rate 1 ml/min, pressure 3.5 MPa and

detection: 470 nm, calibration: external standard (Pcarotene) sample preparation: multiple extraction with

acetone: chloroform (v/v).

The dry matter and total soluble solids were determined on the ripe fruits collected on the second truss

(harvesting). Titratable acidity, Na+, K+, Mg^sup 2+^ and Ca^sup 2+^ were determined on fruits homogenized

at 1000 ? g. Fruits were dried to a constant weight in a forced-draft oven at 65C for determination of the dry

weight. Total soluble solids were determined using a portable reflectometer (Brixstix BX 100 Hs). Acidity was

determined with Potentiometrie titration with 0.1M NaOH to pH 8.1, using 10 ml of juice. Results were

expressed as the percentage of citric acid in the juice. Inorganic cations were determined with ion

chomatography (Dionex Corporation.USA), with CS 12 column (Serio et al., 2003). A higher EC led to the

reduction of the mean weight of fruits by 18%, while the percentage of fruit with a diameter between 25 and 35

was higher on posidonia than rockwool.

After thawing the samples, the juice was prepared for analyses of soluble solids and titrable acidity. Soluble

solids concentration was determined with a digital refractometer (Atago Co, Ltd, Tokyo, Japan), the tritrable

acidity was detected with a radiometer end-point titrator (Radiometer End Point Titration System, ETS 822,

Copenhagen, Denmark), and calculated as citric acid. Dry matter was determined by drying c. 5 g of

homogenized material for 24 h at 104C and weighing after stabilizing at room temperature in an exsiccator

(Wold et al., 2004). The average dry matter for all cultivars was 5.93%. Significant differences were detected

between the cherry tomato and the other the cultivars: post-harvest ripened tomatoes had lower values

compared with the other ripening degrees. For cultivar Liberto dry matter was 5.45% and significantly differed

from the cultivar Favorita with 7.15% dry matter. Soluble solids was 4.39% in Liberto and 3.96% in Durita, both

significantly differed from 5.66% soluble solids of Favorita.Lycopene from tomato products was extracted with hexane, methanol, acetone, 2:1:1, containing 2.5% BHT.

The optical density of the hexane extract was measured spectrophotometrically at 502 nm against a hexane

blank. The concentration of lycopene was calculated using the extinction coefficient (E%) of 3150 (Anon., 1983).

To validate the spectrophotometric method of lycopene estimates, the extract was analyzed with HPLC using

reversed phase C18 column (Vydac 201HS54 Column, Separation Group) and an absorbance detector (Rao et

al., 1998). Lycopene was quantified from HPLC profile by using purified lycopene standard (Sigma Chemical

Co). By applying the abovementioned methods, Rao (1998) showed that lycopene is the main carotenoid in

tomatoes and tomato products. Moreover, a spectrophotometric method was developed for lycopene analysis

which was a much more convenient, fast, and less expensive than HPLC method. Spectrophotometer

measurements were 101.6 ppm of lycopene in tomato juice, 130.6 ppm of lycopene in tomato sauce, and 123.9

ppm of lycopene in ketchup. In contrast, lycopene estimation with HPLC was 116.9 ppm in tomato juice, 156.7

ppm in tomato sauce, 114.9 ppm in ketchup. Frozen diced tomato sample was quickly thawed by placing under



17/36

tap water. The sample was pureed in an Osterizer (Sunbeam-Oster Household Products, Milwaukee, Wise.) for

30 sec and filtered through a cheese cloth and Whatman filter paper (Whatman International Ltd., Maidstone).

The residue was discarded while the filtrate was used for chemical analyses. TA, expressed as percent citric

acid, was determined by diluting 5 ml of the tomato serum to 30 ml and titrating to pH 8.1 with 0.1N NaOH using

a pH meter (Model Accumet, Fisher Scientific, Pittsburgh, Pa.). SS content was determined as Brix with a

table-top reflactometer (Model ABBE-3L, Bausch and Lomb Optical Co, Rochester, N.Y.) (Malundo et al., 1994).The correlation analysis revealed that there was a strong positive correlation between SS and sugar levels, acid

concentration negatively correlated with pH while positively correlating with TA. A positive correlation of sugar

levels with sweet taste was shown, while acid concentration positively correlated with sour taste. However, none

of the component variables could be correlated with fresh tomato impact. Models that predicted the responses

to the descriptive and consumer variables evaluated to sugar and acids levels were for sweet y = 20.19 +

9.23x^sub 1^, for sour y = 21.44 + 73.52x^sub 2^ and for consumer acceptability y = 5.43 + 0.51x^sub 1^ +

2.64x^sub 2^ + 9x^sub 2^ (where y, is a response ofthe dependent sensory variable; x1 = sugar level; and

x^sub 2^ = acid level).

The analysis, separation, and quantification of lycopene were accomplished with HPLC (Arias et al., 2000).

Polymeric carotenoid C80 column (Emenhiser et al., 1995) (YMC. Inc., Wilmington, NC) was used as an

isocratic mobile phase of methyl alcohol (Fisher Scientific) and methyl tert-butyl ether (Sigma Chemical Co., St.

Louis, MO) in a ratio of 3:7. The lycopene standard used was 95% pure (Sigma Chemical Co.) and showed a

retention time of nine min. HPLC grade solvents were filtered using 0.45 m nylon filter membranes and

degassed with helium gas. The HPLC system consisted of a Waters 600 E system controller, a Waters 991

photodiode array detector, a Waters U6 K injector system, and a Waters 600 multisolvent delivery system

(Millipore, Milford, MA). The wavelength range used was 420-530 nm and the lycopene peak was determined at

471 nm. The results showed that the lycopene content and the sensory classification of the ripening stages

produced a good linear regression and an even better fit when an exponential regression was used (Arias et al.,

2000).

A quartz microbalance based electronic nose (E-nose) and a mass spectrometry based electronic nose (MSE-

nose) for tomato aroma profiling were evaluated. The loading plots of PCA revealed that mainly three

discriminant mass to charge ratios (m/z = 93, 43, and 57) were responsible for the observed shelflife effect in

both cultivars. These fragments indicated that-phellandrene, 6-methyl-5-hepten-2-one, 1-nitropentane, and 2-

methylbutanol underwent important concentration changes during the shelf-life of tomatoes. The aroma

differences between cultivars were analyzed by means of the electronic nose systems resulting in a clear



18/36

distinction between the tomato cultivars based on MSE-nose measurements (Berna et al., 2004). The

characteristics of physicochemical analysis employed and respective finding for tomato cultivars are

summarized in Table 5.

Sensory Analysis/Properties

Sensory analysis usually faces the problem of relating data acquired from a number of sources describing a

product. The identification of relationships between sources such as product information, sensory evaluation,and consumer preference and attitude is a key to successful analysis. Partial Least Squares Regression (PLS-

R) is a well-known and useful tool in consumer preference analysis. Three-way PLS regression and 3-block

PLS regression often lead to confusion because of their nearly identical names. Through this study, the

structural differences in the three-dimensional shape of 3-way data compared to the L-shape of 3-block data

were exposed and illustrated. A 3-way PLS regression model was utilized to relate a 3-way sensory data array

of two variable modes: assessors and attributes, to preference ratings of three pre-defined consumer segments.

This analysis enabled the researchers to identify both positive and negative sensory drivers of liking as well as

study the individual assessors performances (Lengard and Kermit, 2006).

Sensory analysis was performed with a panel of 54 trained panelists. Judges were grouped into four panels

(Causse et al., 2001). Three were composed of seed company employees (Clause, Vilmorin, Tezier), with 20, 8,

and 8 panelists, respectively. The fourth panel (DUON) composed of 18 volunteers was already trained in

sensory analysis with other products. This panel conducted three assays per week, while the other three

performed only one. Panelists were trained over 13 assays before the experiment began. Attributes were

selected after 2 years of sensory analysis experimentation with related tomato material. Fruits from Cervil were

considerably more sour, exhibited a stronger overall aroma intensity, a higher lemon and candy aroma, and

were firmer and less-melting than Levovil fruits. F1 showed intermediate values between its two parents lines

for eight attributes (sweetness, sourness, candy aroma, lemon aroma, citrus-fruit aroma, pharmaceutical aroma,

meltiness, juiciness), although often closer to Cervil than to Levovil.

The performance of a quartz microbalance based electronic nose (E-nose) and a mass spectrometry based

electronic nose (MSE-nose) for tomato aroma profiling was evaluated (Berna et al., 2004). Solid phase micro-

extraction (SPME) headspace sampling combined with gas chromatography (GC) was effectively used as a

reference method. The changes in tomato aroma profiles of two different cultivars were monitored versus their

shelf-life (Days 1, 8, 12, and 19). The tomato aroma profiles measured on Days 1 and 8 could not be

discriminated with E-nose. In contrast, MSE-nose score plots indicated an evident change in aroma profile with

shelf-life. It was also found that P-phellandrene, 6-methyl-5-hepten-2-one and 1- nitropentane underwent

important concentration changes versus tomato shelf-life.

A selected group of seven assessors (n = 7) were trained to carry out a descriptive test, conventional profiling,

on the tomatoes (Stone and Sidel, 1993). The assessors developed a list of profiling attributes and agreed onthe following attributes; consistency, firmness, and juiciness and for tomato taste intensity, sweetness,

bitterness, and acidulous (ISO, 1992) taste. Before profiling the tomatoes, the assessors were trained to

recognize tomato taste intensity at different levels by being presented with tomatoes at various ripeness stage.

No significant effects of variety were found regarding juiciness, acidulous, and bitter taste, while significant

differences were detected for firmness. The correlation between the growing system and the variety for the

attribute sweet taste indicated that the ecologically grown tomato varieties were significantly different in sweet

taste, while no difference was found between the same varieties when grown conventionally (Johanson et al.,

1999).

Employment of gas chromatography-olfactometry (GC-O) and aroma extract dilution analysis resulted in the

detection of 34 aroma compounds found with flavor dilution factors_4. (Z)-3-hexenal, hexanal, l-octen-3-one,

methional, 1-penten-3-oneand 3-methylbutanal belong to the most odor-active aroma volatiles in fresh tomatoes

(Krumbein and Auerswald, 1998). Smell, taste, and aftertaste of different tomato cultivars were evaluated by



19/36

quantitative descriptive analysis (QDA)). By applying principal component analysis to both sensory attributes

and chemical compounds (odor-active aroma volatiles, titratable acid, and reducing sugars) the first three

components explained 70% of the total variance. On the basis of aroma volatiles (normalized GC-MS peak

area) tomato cultivars could be separated into four clusters: "Pronto," "Gourmet," "Selfesta," "Vanessa,"

Stamm157/93 (cluster 1), "Super-sweet 100" and "Mickey" (cluster 2), DRW3 126F1 (cluster 3), LYC1045/90

(cluster 4). Significant differences among cultivars were found in the attributes: sourness, sweetness, spoiled-sweetish, raw potato, bitterness, fruitiness, mustiness, and tomato leaf.

An electronic nose based on metalloporphyrin-coated quartz microbalance sensors and a trained panel of

seven human assessors in the evaluation of gases derived from degradation reactions in tomatoes have been

evaluated (Sinecio et al., 2000). Performances are measured in terms of capability of both systems to

distinguish samples of different quality coming from conventional and organic production systems. It was found

that both sensory and instrumental measures were qualitatively valid for detection of odor defects, but the

panel's ability to discriminate between classes close in quality was worse than the electromc nose results;

although the variation in sensory data was higher than usual, their normalization improved the situation (Sinecio

et al., 2000). The effect of three concentrations of nutrient solution (electrical conductivity, EC: 1.0, 3.5, and 6.0

dS/m) on the sensory properties of tomato was investigated by Auerswald and his coworkers (1999).

Comprehensive analysis of sensory attributes of tomato fruits with quantitative descriptive analysis by trained

panel (Stone and Sidel, 1993) and the acceptance test by consumers were both part of the sensory

investigations. For the "Vanessa" variety, higher EC led to a much stronger intensity of flavor attributes like

mouldy, spoiled sweetish, bitter, and for the aftertaste attributes like mouldy and burning, thus leading to off-

flavor. In contrast, for "Counter" higher EC led to a more intense fruity flavor, enhanced firmness of the whole

fruit, and fruit flesh, and increasing juiciness were assessed to improve fruit quality by consumers.

The effect of short-term storage of tomatoes (air temperature 20C, relative air humidity 55%, air velocity


20/36

growing systems when harvested at comparable maturity. This means that different cropping systems such as

the confined or the combined system can be employed without changing the eating quality of tomatoes

significantly. This improves the possibilities for organic growers of tomatoes to switch to a compost bed system

in order to control soil borne pests and diseases and to improve the nutrient balance in an intensive greenhouse

production system (Thybo et al., 2006).

All the information regarding the sensory analysis of tomato such as number of panelists (trained or untrained),scale employed, and attributes selected are given in Table 6.

Storage Properties

The growth/survival results of Salmonella Enteritidis at spotinoculated or stem-injected cherry tomatoes during

passive modified atmosphere packaging (MAP), and a controlled atmosphere (CA), were analyzed and

compared with those of air storage at 7 and 22C. During MAP, the gas composition equilibrated to 6% O2/4%

CO2. CO2 level was maintained as 5% through the term of CA storage at 7 and 22C. The results

demonstrated that S. Enteritidis can survive and/or grow during the storage of tomatoes depending on the

location site of the pathogen on fruit, suspension cell density, and storage temperature. During MAP, CA, and

air storage, S. Enteritidis with an initial population of 7.0 log10 cfu/tomato survived on tomato surfaces with an

approximate decrease of 4.0-5.0 log 10 cfu/tomato in population within the storage period; however, in the case

of the initial population of 3.0 log10 cfu/tomato, cells died completely on day 4 during MAP storage and on day 6

during both CA and air storage. The death rate of S. Enteritidis on the surfaces of tomatoes that were stored in

MAP was faster than that stored in air and in CA. Storage temperature was effective on the survival of S.

Enteritidis for the samples stored at ambient atmosphere; cells died completely on day 6 at 7C and on day 8 at

22C. Stem scars provided protective environments for Salmonella; an approximate increase of 1.0 log 10

cfu/tomato in stem-scar population was observed during MAP, CA, and air storage at 22C within the period of

20 days. Cells survived with no significant change in number at 7C. The effect of ozone treatment (5-30 mg/l

ozone gas for 0-20 min) was also considered for surface sanitation before storage. Ten mg/l ozone gas

treatment with different time intervals of 5 and 15 min was found to be effective respectively on low and high

dose inoculum levels of S. Enteritidis attached for 1 h (Das et al., 2006).

Dermesonlouoglou and his coworkers (2006) showed that the quality of frozen tomato (osmotically pretreated

with alternative osmotic solutes; glucose, maltodextrin, can significantly be improved by means of osmotic

dehydration as a prefreezing treatment. The objective of this work was to study the effect of osmotic

pretreatment with alternative osmotic solutes-glucose, a high DE maltodextrin (HDEM), oligofructose, and

trehaloseon the quality and functional properties of frozen tomato tissue. Color, the vitamin C content, and

texture characteristics of pretreated and conventionally frozen samples were comparatively measured at 3, 6,

and 12 months, during storage at two temperatures, -12 and -20C. Sensory evaluation of samples was also

conducted. The results indicate that osmodehydrofrozen compared to conventionally frozen sliced tomatoesshow improved quality and functional characteristics for a prolonged storage period. For tomato samples pre-

treated with glucose, HDEM, oligofructose, and oligofructose/trehalose and stored at -20C during 12 months,

the retention of initial vitamin C content was 81%, 66%, 77%, and 88%, while for frozen, untreated, and

blanched, products it was lower (44% and 58%), respectively. Sensory evaluation showed good organoleptic

quality in osmodehydrofrozen tomato slices.

The maturity stages of commercially grown tomatoes (breaker and mature green) were exposed to ethanol

vapor (2 ml ethanol/kg fruit) for 6 h at 20C. During storage the color, firmness, and composition changes were

determined every 3 and 7 days (Yanuriati et al., 1998). The results revealed that ethanol vapor treatment

slowed down the color changes and softened both mature green and breaker tomatoes with greater effects

when stored at 5C. No difference was observed between the two maturity stages in the retardation of softening

during storage. In contrast, the maturity stage had a highly significant effect on the color development of stored

tomatoes. When the fruit stored at 5C was then held at 20C for 7 days the ripening process was accelerated



21/36

but the fruit did not reach the same level of color development compared to the fruit stored continuously at

20C. The results suggested that ethanol vapor pre-treatment could be used as a low cost and easy to apply

method towards extending the storage life of tomatoes.

Suparlan and Itoh (2003) reported that the application of HWT (hot Water Treatment) before storage in MAP

(Modified Atmosphere Packaging) prevented both the decaying and the cracking of tomatoes. A significant

difference was recorded between decay of hot water-treated tomatoes and that of untreated tomatoes packaged

with plastic film. Moreover, HWT prior to storage in MAP slightly reduced mould growth. However, both treated

and untreated tomatoes packaged with plastic film resulted in higher microbial count than unpackaged

tomatoes. A significant difference was reported between the microbial counts of packaged and unpackaged

tomatoes. Furthermore, there was no statistically significant difference between the microbial counts of treated

and untreated tomatoes packaged with polyethylene film. The microbial count of heat treated tomatoes

packaged in polyethylene film was 2.57 logcfu/g, that of untreated tomatoes packaged in polyethylene film was

3.44 logcfu/g, and that of unpackaged tomatoes amounted to 0.81 logcfu/g. The lower microbial count of the hot

water treated tomatoes showed that treatment with hot water prior to packaging in plastic film and storage had a

disinfecting effect, thus resulting in reduction of microbial growth and decay.

Auerswalt and his coworkers (1998) studied the quality changes of tomatoes harvested red during short-term

storage of 4 and 7 days (storage conditions: air temperature 20C, relative air humidity 55%, air velocity


22/36

"mouldy" and "spoiled sweetish" increased too.

Efiuvwevwere and Uwanogho (1990) found that the incidence of spoilage was higher in control tomatoes

followed by basket-packaged fruits and lowest in LDPE packaging fruits. Fruits spoilage increased with storage

time, being higher in ethanol treated tomato fruits than benomyl-treated ones. The consistently low occurrence

of spoilage in LDPE-packaged fruits suggests that this material is more suitable for tomato packaging during

retail marketing under tropical conditions, and this could be related to its water vapor transmission rate (WVTR)and gas permeability properties. The high incidence of spoilage (>50%) in ethanol-treated fruits disclosed the

ineffectiveness of this treatment, thereby suggesting that benomyl is more effective.

A slight decrease in acid content (~3.5%) was detected in tomato juice packed in plain tinplate cans, whereas

no change was observed in the same tomato juices packed in lacquered cans after 27 months of storage at

36C (Yaron and Feigin, 1992). Also, the chloride content in either type of can was unchanged by processing

and storage as compared with the initial values of the tomato raw material, indicating that the only effect on the

chloride content and retention in canned tomato juice is via the combined interaction of the NO^sub 3^ (1-110

mmol/liter) and Cl (5-110 mmol/liter) levels of nutrient solutions.

Mutations drastically slowing down tomato fruit ripening known as "ripening inhibitor" (rin) and "non-ripening"

(nor) have been incorporated by backcrossing into isogenic lines of the tomato cultivar Alisa Craig (Richardson

and Hobson, 1987). Fl hybrics (rin/+ and nor/+) were then produced by crossing with the recurrent parent.The

rates of deterioration or the fruit from the hybrid plants were compared with those from the recurrent parent and

a typical glass-house cultivar, Sonatine. Levels of acids and sugars, and also the color, the firmness, and the

dry matter content of the fruit, were determined at two selected stages of ripeness and after storage of the ripe

fruit for 10 and 20 days at 20C. The shelf-life of ripe fruit was also determined. Although the acidity fell

continuously from a high value early in ripening for all four lines, during storage that in the rin/+ was better and

Sonatine was worse than average. Sugar levels generally peaked close to the red stage and fell thereafter, but

much variabitity in this component was reported. Both cv. Sonatine and Alisa Craig overcolored and lost

firmness during storage, but the mutant lines survived well. The results suggested that the disadvantage of a

high-quality line such as Alisa Craig in terms of fast deterioration once the fruits are fully ripe could be at least

partially overcome through the introduction of one of the "non-ripening" alleles.

The effects of calcium chloride washings and passive or active modified atmosphere packaging (MAP) on

quality preservation of fresh-cut tomato were investigated by Artes and his coworkers (1999). When slices were

stored at 10C, both passive and active MAP delayed considerably the rate of ripening. The best results were

found during storage at 20C under active and passive MAP. Calcium chloride dips proved useful only at 2C in

maintaining quality of tomato slices held in the perforated film. Active MAP should be used for maintaining fresh-

cut tomato when stored at 10C.

Tomatoes (cv. Tradiro), harvested at two maturity stages, were stored at four different temperatures during upto four weeks. Apart from the lowest storage temperature that caused chilling injury, the rest of the three applied

temperatures did not cause similar problems. During storage Near Infrared spectra of intact tomatoes were

recorded and samples were taken at regular time intervals, to determine the activities of the pectolytic enzymes

polygalacturonase, pectin methyl esterase and b-galactosidase. The maturity stage of the tomatoes at harvest,

followed by storage at the four different temperatures affects the activities of these enzymes. To describe the

change in activity of these enzymes, kinetic models were built based on fundamental laws of chemical kinetics

using assumed, but plausible reaction mechanisms. For the models developed, a fixed and a variable enzyme

activity were observed for these three enzymes. For polygalacturonase, this fixed amount of enzyme activity

was dependent on the maturity stage at harvest. For pectin methyl esterase and P-galactosidase the maturity at

harvest had almost no effect on this fixed amount of enzyme activity. The variable part of the enzyme activity

could either increase in time (polygalacturonase), followed by denaturation (P -galactosidase), or only decay in

time (pectin methyl esterase). For the activity of polygalacturonase, a self-initiated, autocatalytic production of



23/36

this enzyme was assumed. P-Galactosidase was formed, but inactivated in time. Pectin methyl esterase activity

decayed exponentially in time. The models for polygalacturonase and P-galactosidase were integrated into the

previously developed model for the firmness loss of tomatoes during storage (Van Dijk et al., 2006a). It was

concluded that any cell wall degrading enzyme, whose activity remains within a certain bandwidth, can be

integrated into the firmness model to explain the observed firmness decay. Based on Near Infrared

spectroscopy, a statistically significant relation was only observed between the polygalacturonase activity andthe Near Infrared spectra of intact tomatoes. It is argued that the consequences of the performed

polygalacturonase activity are reflected in this relation rather than the amount of this enzyme. Since mutual

statistically significant relations exist between Near Infrared spectra, polygalacturonase activity, and the tomato

firmness, it seems reasonable to ascribe a significant role of this enzyme to the firmness decay (Van Dijk et al.,

2006b). Table 7 gives a synoptical presentation of tomato storage methodology (method description and

thereby ensuing results).

GENETICALLY MODIFIED TOMATO

The Flavr savr(TM) tomato was the first genetically modified product entering the commerce being itself a

genetically modified organism (GMO). Since then, at least 40 other genetically engineered agricultural crops

have been approved by US authorities and in other countries (Arvanitoyannis, 2003). These genetically

engineered plants can be categorized as follows:

i) Improved product quality (durability, firmness, fruit ripening delayed),

ii) Pest resistance (insects, nematodes, and viruses),

iii) Agronomic benefits (herdicide tolerance, hybrid system).

The Flavr savr(TM) tomato belongs to the first category (Hemmer, 1997). This tomato contained an artificially

introduced gene that was transcribed into a messenger RNA (mRNA) anti-sense to mRNA from the

polygalacturonase (PG)-gene. The complementary in vivo base pairing of these two molecular species resulted

in inhibition of the expression of the gene, with a dramatically decreased PG-activity in the transgenic tomatoes.

The enzyme PG degraded pectin, a major constituent of the cell wall of the fruit. Its inhibition increased the self-

life of the tomatoes and prevented them from becoming soft (Lthy, 1999).

The maize transcription factors LC and Cl were simultaneously overexpressed in tomato with the aim to

producing lines with enhanced concentration of flavonols. The metabolite composition of these genetically



24/36

modified tomatoes has been compared with that of azygous (non-modified) controls grown side-by-side under

the same conditions (Gall et al., 2003). It has been possible to observe metabolic changes in both types at differ

stages of maturity. NMR spectra showed that the levels of glutamic acid, fructose, and some specific amino

acids such as valine and i- aminobutyric acid were present in higher amounts in unripe tomatoes. Apart from the

significantly increased content of six main flavonoid glycosides, the levels of at least 15 other metabolites were

found to differ considerably between the two types of red tomato. Among the varying metabolites were citricacid, sucrose, phenylalanine, and trigonelline.

Fruit taste is an important component of fruit quality, but its genetic basis is complex, making difficult its

alteration by plant breeding. Thaumatin is a sweet tasting flavor-enhancing protein produced by fruits of the

African plant Thaumatococcus dantellii Benth. Agrobacterium-mediated transformation was used to produce two

transgenic tomato lines expressing biologically active thaumatin in fruits (Bartoszewski et al., 2003). Transgenic

tomato fruits from the T^sub 2^ plant generation were sweeter than the controls and possessed a specific

aftertaste as determined with sensory evaluation. These results demonstrated that transgenic expression of

thaumatin could be eventually useful for modifying tomato fruit taste, especially in breeding lines of poor fruit

taste, such as those carrying a non-ripening (nor) mutation.

Tomato plants, which normally do not accumulate glycine betaine (GB), are susceptible to chilling stress.

Exposure to temperatures below 10C causes various injuries and greatly decreases fruit set in most cultivars.

Tomato (cv. Moneymaker) had been transformed with a chloroplast-targeted coodA of Arthobacter globiformis,

which encodes choline oxidase to catalyze the conversion of choline to GB (Park et al., 2004). These transgenic

plants express coodA and synthesize cloline oxidase, while accumulating GB in their leaves and reproductive

organs up to 0.3 and 1.2 mol/g fresh weight (FW), respectively. Their chloroplasts contain up to 86% of total

leaf GB. Over various development phases, from seed germination to fruit production, these GB-accumulating

plants are more tolerant of chilling stress than their wild-type counterparts. During reproduction, their yield,

amounts to 10-30% more fruit following chilling stress. Endogenous GB contents as low as 0.1 mol/g FW were

apparently sufficient to confer high levels of tolerance in tomato plants, as achieved with the coodA gene.

Exogenous application of either GB or H^sub 2Ô^sub 2^ improved both chilling and oxidative tolerance

concomitant with enhanced catalase activity. These moderately enhanced levels of H^sub 2Ô^sub 2^ in coodA

transgenic plants, as byproducts of choline oxidase-catalyzed GB synthesis, might activate the H^sub 2Ô^sub

2^ inductively protective mechanism, resulting in improved chilling and oxidative tolerances in GB-accumulating

coodA transgenic plants. Therefore, the introduction of the biosynthesis pathway of GB into tomato through

metabolic engineering is an effective strategy towards improving chilling tolerance.

The genetic manipulation of both mevalonic acid (MVA) and methylerythritol - 4-phosphate (MEP) pathways,

leading to the formation of isopentenyl diphosphate (IPP), were achieved in tomato using 3-

hydroxymethylglutaryl CoA (hmgr-1) and 1-deoxy-D-xylulose-5-phosphate synthase (dxs) genes, respectively(Enfissi et al., 2005). Transgenic plants containing additional hmgr-1 from Arabidopsis thaliana, under the

control of the cauliflower mosaic virus (CaMV) 35S constitutive promoter, contained elevated phytosterols (up to

2.4-fold), but IPP-derived isoprenoids in the plastid were unaltered. Transgenic lines containing a bacterial dxs

targeted to the plastid with the tomato dxs transit sequence resulting in an enhanced carotenoid content (1.6-

fold), inherited in the next generation. It is noteworthy that phytoene and P-carotene exhibited the greatest

increases (2.4and 2.2-fold, respectively). Extraplastidic isoprenoids were unaffected in these lines. Many

isoprenoids are of biotechnological and health-related importance. Carotenoids and tocopherols are associated

with benefits to human health reducing the onset of chronic disease states such as cancer, macular

degeneration, and cardiovascular disease (Sies and Krinsky, 1995).

Survey researchers indicated that gene technology applied to the food sector is considered less useful than

other applications. Recently theoretical approaches, such as the Theory of Reasoned Action (TRA) and the

Theory of Planned Behavior (TPB), have been applied to assess attitudes towards using gene technology in



25/36

food production. A recent study (n = 1000 subjects) aimed at assessing beliefs and attitudes towards eating

tomatoes produced by gene technology in the nearest future, was carried out in Italy (Saba and Vassallo, 2002).

The basic frame of reference for design and analysis was the TRA. Patterns of perceived behavioral control and

moral obligation components were included into the model. Most subjects of samples tended to express

negative attitudes toward consuming tomatoes produced by gene technology. Furthermore, a strong predictive

link was found between beliefs and attitudes and between perceived behavioral control and intention ofconsuming tomatoes produced by gene technology. The parameter of moral obligation proved to be a no-

significant predictor of intention.

Repetitive extragenic palindromic (REPs) sequences were first described in enterobacteriacea and later in

Pseudomonas putida. A new variant (51 base pairs) of REP sequences that appears to be disseminated in

more than 300 copies in the Pseudomonas syringae DC3000 genome was detected. The findings of REP

sequences in P. syringae confirm the broad presence of this type of repetitive sequence in bacteria. The

distribution of REP sequences and the structure of the clusters were analysed thus showing that palindromy is

conserved. REP sequences appear to be allocated to the extragenic space, with a special preference for the

intergenic spaces limited by convergent genes, while their presence is scarce between divergent genes. Using

REP sequences as markers of extragenicity we re-annotated a set of genes of the P. syringae DC3000 genome

demonstrating that REP sequences can be used for refinement of annotation of a genome. The similarity

detected between virulence genes from evolutionarily distant pathogenic bacteria suggests the acquisition of

clusters of virulence genes by horizontal gene transfer. No presence of P. syringae REP elements in the

principal pathogenicity gene clusters was detected. This absence suggested that genome fragments lacking

REP sequences could point to regions recently acquired from other organisms, and REP sequences might be

new tracers for gaining insight into key aspects of bacterial genome evolution, especially when studying

pathogenicity acquisition. Furthermore, as the P. syringae REP sequence is species-specific with respect to the

sequenced genomes, it is an exceptional candidate for use as a fingerprint in precise genotyping and

epidemiological studies (Tobes and Pareja, 2005).

In a recent review article published within the frame of a

a review on tomato authenticity quality control methods in conjunction with multivariate analysis...

Documents

discriminant analysis

canonical analysis

cluster analysis

factor analysis

b sensory analysis

food quality

applied methods

authenticity inparticular