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UNIVERSITI PUTRA MALAYSIA
DEVELOPMENT OF AN IMPROVED PITAYA JUICE PROCESSING SYSTEM
NUR ‘ALIAA BINTI ABD RAHMAN
FK 2009 1
DEVELOPMENT OF AN IMPROVED PITAYA JUICE PROCESSING SYSTEM
By
NUR ‘ALIAA BINTI ABD RAHMAN
Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia, in Fulfilment of the Requirements for the Degree of Master of Science
May 2009
ii
Specially dedicated to….
My loving parents…
My beloved husband…
My wonderful siblings…
My friends…
for their support and encouragements…
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Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfilment of the requirements for the Degree of Master of Science
DEVELOPMENT OF AN IMPROVED PITAYA JUICE PROCESSING
SYSTEM
By
NUR ‘ALIAA BINTI ABD RAHMAN
May 2009
Chairman: Siti Mazlina Mustapa Kamal, PhD
Faculty: Engineering
The processing of tropical fruit juice has improved nowadays. Dragon fruit or pitaya
is one of the tropical fruits that has attracted the attention of consumers, fruit growers
and also food processing industry entrepreneurs in this country. Various pitaya
products have been marketed in Malaysia. Pitaya juice is well known for its health
benefits. Since pitaya processing has just developed, more research should be carried
out to increase the production quality of pitaya product such as fruit juice. In the
current research, pitaya juice production operations were studied from the peeling
process to the production of clear pitaya juice using enzyme. A fruits grater and
peeler was invented to ease the peeling process before the fruit is processed into
juice. The machine was able to reduce the peeling time up to 94% when compared to
manual peeling. This apparatus was proven to ease and speed up the process of
peeling pitaya skin. Studies were carried out to obtain the optimum processing
condition for enzymatic clarification of red and white pitaya juices. Two types of
commercial pectinase enzymes had been used which were Pectinex Ultra SP-L and
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Pectinex CLEAR. Response Surface Methodology (RSM) was used to obtain the
optimum processing condition in terms of enzyme concentration, temperature and
incubation period. The optimum processing condition for enzymatic treatment of red
pitaya juice treated with Pectinex Ultra SP-L was found to be at 0.10% enzyme
concentration at 40oC for 45 min. The optimum processing condition of red pitaya
juice treated using Pectinex CLEAR was reported in other study. For white pitaya
juice, the optimum processing condition for enzymatic treatment using Pectinex
Ultra SP-L was at 0.06% enzyme concentration at 49oC for 40 min. For white pitaya
juice treated with Pectinex CLEAR, the optimum processing condition was at 0.10%
enzyme concentration at 40oC for 82 min. The use of this enzyme was proven to
increase the recovery of pitaya juice after the filtration process. The data for pitaya
composition after processing was also obtained. It was observed that several
components such as protein and phenolic contents (antioxide component) had
increased after the enzymatic treatment. Research was carried out further by
developing a process flow sheet for producing pitaya juice at laboratory-scale (batch
processing). Laboratory-scaled processing was carried out to resemble large-scaled
continuous processing in the industry. Calculation of material balance was also done
based on the process flow sheet that had been developed. Data obtained from this
research can be used as a base for developing large-scale pitaya juice production
process at industrial level.
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Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai memenuhi keperluan untuk Ijazah Master Sains
PEMBANGUNAN SISTEM PEMPROSESAN JUS PITAYA YANG
DIPERTINGKATKAN
Oleh
NUR ‘ALIAA BINTI ABD RAHMAN
Mei 2009
Pengerusi: Siti Mazlina Mustapa Kamal, PhD
Fakulti: Kejuruteraan
Pada masa kini, pemprosesan jus buah-buahan tropikal telah semakin meningkat
maju. Buah naga atau pitaya adalah salah satu daripada buah tropikal yang mula
mendapat perhatian di kalangan pengguna, penanam buah, dan juga pengusaha
industri pemprosesan makanan di negara ini. Pelbagai produk hasil pitaya telah mula
dipasarkan di Malaysia. Jus pitaya juga telah dikenali kerana khasiat kesihatannya.
Oleh kerana pemprosesan pitaya baru sahaja berkembang, maka pelbagai kajian
perlu dilakukan untuk meningkatkan kualiti pengeluaran produk pitaya seperti jus
buah. Dalam penyelidikan ini, operasi penghasilan jus pitaya telah dikaji dari proses
pengupasan pitaya kepada penghasilan jus pitaya jernih menggunakan enzim. Sebuah
alat pemarut dan pengupas kulit pitaya telah direka bagi memudahkan proses
pembuangan kulit pitaya sebelum diproses untuk menjadi jus. Alat ini dapat
mengurangkan tempoh pengupasan buah sehingga 94% berbanding dengan
pengupasan secara manual. Penghasilan alat ini terbukti dapat memudahkan dan
mempercepatkan lagi proses pengupasan kulit pitaya. Kajian turut dijalankan untuk
memperoleh keadaan pemprosesan yang optimum bagi proses rawatan berenzim jus
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pitaya merah dan putih. Dua jenis enzim pektinase komersil telah digunakan iaitu
Pectinex Ultra SP-L dan Pectinex CLEAR. Response Surface Methodology (RSM)
telah digunakan bagi memperoleh keadaan pemprosesan optimum dari segi
kepekatan enzim, suhu dan tempoh masa inkubasi. Keadaan pemprosesan optimum
bagi rawatan berenzim jus pitaya merah oleh Pectinex Ultra SP-L adalah pada
kepekatan enzim 0.10%, pada suhu 40oC selama 45 minit. Keadaan pemprosesan
optimum bagi jus pitaya merah yang dirawat menggunakan Pectinex CLEAR telah
dilaporkan di dalam kajian lain. Bagi jus pitaya putih, keadaan pemprosesan
optimum bagi rawatan berenzim menggunakan Pectinex Ultra SP-L adalah pada
kepekatan enzim 0.06%, pada suhu 49oC selama 40 minit. Bagi jus pitaya putih yang
dirawat oleh Pectinex CLEAR, keadaan pemprosesan optimum adalah pada
kepekatan enzim 0.10%, pada suhu 40oC selama 82 minit. Penggunaan enzim ini
telah terbukti dapat meningkatkan lagi pemerolehan semula jus pitaya selepas
melalui proses penapisan. Data-data bagi komposisi pitaya selepas diproses juga
telah diperoleh. Didapati bahawa beberapa komponen seperti protein dan fenolik
(komponen antioksida) telah meningkat selepas dirawat dengan enzim. Kajian
diteruskan lagi dengan pembangunan helaian aliran proses bagi penghasilan jus
pitaya berskala makmal (pemprosesan berkelompok). Pemprosesan berskala makmal
ini dijalankan bagi menyerupai pemprosesan berskala besar di industri yang
menjalankan pemprosesan secara terus-menerus (continuous). Pengiraan terhadap
keseimbangan bahan juga telah dijalankan berdasarkan pada helaian aliran proses
yang telah dibangunkan. Data yang diperoleh dari kajian ini dapat dijadikan asas
kepada pembangunan proses penghasilan jus pitaya berskala besar di peringkat
industri.
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ACKNOWLEDGEMENTS
I would like to express my gratitude to Allah S.W.T. for His entire blessings towards
me and all the strength that He gave me in finishing this study.
My sincere appreciation goes to the members of my supervisory committee, Dr. Siti
Mazlina Mustapa Kamal (Chairman) and Dr. Farah Saleena Taip for their guidance,
constructive comments and assistance during my study. A special thanks to all the
staffs of the Department of Process and Food Engineering and to all of my friends for
their supports.
My deepest gratitude goes to my husband, Mohd Hafizul bin Ismail for his love,
support and encouragement. Million thanks to my loving parents, Abd Rahman bin
Said and Wan Zaharah Megat Hashim, my siblings and family in laws for their
continuous support. May Allah S.W.T. bless all of us.
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I certify that a Thesis Examination Committee has met on 6th May 2009 to conduct the final examination of Nur ‘Aliaa binti Abd Rahman on her thesis entitled ‘Development of An Improved Pitaya Juice Processing System’ in accordance with the Universities and University Colleges Act 1971 and the Constitution of the Universiti Putra Malaysia [P.U.(A) 106] 15 March 1998. The Committee recommends that the student be awarded the Master of Science. Members of the Thesis Examination Committee were as follows: Mohd Nordin Ibrahim, PhD Associate Professor Faculty of Engineering Universiti Putra Malaysia (Chairman) Ling Tau Chuan, PhD Associate Professor Faculty of Engineering Universiti Putra Malaysia (Internal Examiner) Chin Nyuk Ling, PhD Lecturer Faculty of Engineering Universiti Putra Malaysia (Internal Examiner) Ida Idayu Muhamad, PhD Associate Professor Faculty of Chemical and Natural Resources Engineering Universiti Teknologi Malaysia (External Examiner) ________________________________ BUJANG KIM HUAT, PhD Professor and Deputy Dean School of Graduate Studies Universiti Putra Malaysia Date: 29 May 2009
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This thesis was submitted to the Senate of Universiti Putra Malaysia and has been accepted as fulfilment of the requirement for the degree of Master of Science. The members of the Supervisory Committee were as follows: Siti Mazlina Mustapa Kamal, PhD Senior Lecturer Faculty of Engineering Universiti Putra Malaysia (Chairman) Farah Saleena Taip, PhD Senior Lecturer Faculty of Engineering Universiti Putra Malaysia (Member) ________________________________ HASANAH MOHD GHAZALI, PhD Professor and Dean School of Graduate Studies Universiti Putra Malaysia Date: 8 June 2009
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DECLARATION
I declare that the thesis is my original work except for the quotations and citations which have been duly acknowledge. I also declare that it has not been previously, and is not concurrently, submitted for any other degree at Universiti Putra Malaysia or other institutions. _________________________________ NUR ‘ALIAA BINTI ABD RAHMAN Date: 20 May 2009
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TABLE OF CONTENTS
Page DEDICATION ii ABSTRACT iii ABSTRAK v ACKNOWLEDGEMENTS vii APPROVAL viii DECLARATION x LIST OF TABLES xiv LIST OF FIGURES xvi LIST OF ABBREVIATIONS xx CHAPTER 1 INTRODUCTION 1
1.1 Fruit Juice Consumption 1 1.2 Pitaya 2 1.3 Enzymatic Clarification of Fruit Juice 3 1.4 Fruit Processing Operation 4 1.5 Problem Statements 5 1.6 Scope of the Project 6
1.7 Objectives 8 2 LITERATURE REVIEW 9 2.1 Pitaya 9
2.1.1 Pitaya Cultivation 9 2.1.2 Pitaya Fruits, Flowers and Branches 11 2.1.3 The Benefits 15
2.2 Fruit Juice Production 16 2.3 Fruit Juice Clarification 21
2.4 Fruit Peeling Process 23 2.5 Product Design Procedure 26
2.5.1 Concept Development Process 27 2.5.2 Identifying Customer Needs and Establishing 27
Target Specifications 2.5.3 Concept Generation 27
2.5.4 Concept Selection 28 2.5.4.1 Concept Screening 30 2.5.4.2 Concept Scoring 32
2.5.5 Concept Testing and Setting Final Specifications 33 2.6 Food Process Design 33
2.6.1 Preliminary Study 34 2.6.2 Process Chart 35 2.7 Material Balance 37
2.8 Summary of Literature Review 38
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3 DESIGN OF FRUITS GRATER AND PEELER 39 3.1 Introduction 39
3.2 Methods 40 3.2.1 Structure of Fruits Grater and Peeler 41 3.2.2 Conceptual Design 42 3.2.3 Concept Selection 45
3.3 Description of the Invention 50 3.4 Testing of Several Fruits and Vegetable Peeling Process 53 3.5 Summary and Conclusions 54
4 OPTIMIZATION OF ENZYMATIC CLARIFICATION OF 55 PITAYA JUICE 4.1 Introduction 55 4.2 Materials 56 4.3 Methods 57 4.3.1 Juice Extraction Process 57 4.3.2 Enzymatic Treatment 57 4.3.3 Physical Analysis 58 4.3.4 Experimental Design 60 4.3.5 Comparison on the Quality of Pitaya Juice 62
Produced using Two Commercial Enzymes 4.4 Results and Discussion 62 4.4.1 Enzymatic Clarification of Red Pitaya Juice 62
(Pectinex Ultra SP-L) 4.4.2 Comparison on the Quality of Red Pitaya Juice 70
Produced using Two Commercial Enzymes 4.4.3 Enzymatic Clarification of White Pitaya Juice 71 4.4.4 Comparison on the Quality of White Pitaya Juice 83
Produced using Two Commercial Enzymes 4.5 Selection of Filtration Apparatus 84
4.6 Determination of Several Properties of Pitaya Juice 85 4.6.1 Materials 85 4.6.2 Production of Pitaya Juice at Laboratory-Scale 86 4.6.3 Determination of Chemical Composition and Some 88 Physicochemical Properties of the Juice 4.6.4 Determination of Vitamin C and Total Polyphenols 88 4.6.5 Results and Discussion 89
4.7 Summary and Conclusions 99 5 DEVELOPMENT OF A PROCESS FLOW SHEET OF PITAYA 102 JUICE PROCESSING 5.1 Introduction 102 5.2 Methods 102
5.2.1 Operation Process Chart for Pitaya Juice Production 103 5.2.2 Flow Process Chart for Pitaya Juice Production 107
5.3 Results and Discussion 109 5.3.1 Process Flow Sheet of Pitaya Juice Processing 109
5.3.2 Material Balance of Pitaya Juice Production 114 5.4 Summary and Conclusions 118
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6.0 SUMMARY, CONCLUSIONS AND RECOMMENDATIONS FOR 120 FUTURE RESEARCH
6.1 Summary and Conclusions of Research 120 6.2 Recommendations for Future Research 122 BIBLIOGRAPHY 123 APPENDICES 129 BIODATA OF STUDENT 131 LIST OF PUBLICATIONS, PROCEEDINGS, PATENT AND AWARDS 132
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LIST OF TABLES
Table Page
2.1 Grading of dragon fruit 14
2.2 Pitaya nutrition 16
3.1 Structure of fruits grater and peeler 41
3.2 Features of concepts A, B, C, D and E 42
3.3 Specifications of the apparatus 52
3.4 Average size and peeling time of several fruits and vegetable 53
4.1 The Box-Behnken experimental design (in coded level of 61 three variables) for enzymatic clarification of pitaya juice 4.2 Regression coefficient, R2 and coefficient values for FOUR 64 dependent variables for clarified red pitaya juice (Pectinex Ultra SP-L) 4.3 Changes in main physicochemical characteristics of red 70
pitaya juice produced using different enzymes
4.4 Regression coefficient, R2 and coefficient values for FOUR 72 dependent variables for clarified white pitaya juice
(Pectinex Ultra SP-L)
4.5 Regression coefficient, R2 and coefficient values for FOUR 73 dependent variables for clarified white pitaya juice
(Pectinex CLEAR)
4.6 Changes in main physicochemical characteristics of white 83 pitaya juice produced using different enzymes 4.7 Optimum processing conditions for enzymatic clarification of 87 red pitaya pulp 4.8 Optimum processing conditions for enzymatic clarification of 87 white pitaya pulp 4.9 Yield, physical and physicochemical properties of red pitaya 91 juice 4.10 Yield, physical and physicochemical properties of white pitaya 92 juice
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4.11 Chemical composition of red pitaya juice 94
4.12 Chemical composition of white pitaya juice 94
4.13 Vitamin C and total polyphenols contents of red pitaya juice 97
4.14 Vitamin C and total polyphenols contents of white pitaya juice 97
5.1 Difference in peeling time for two methods 112
5.2 Optimum process condition for enzymatic clarification of red 112 pitaya pulp 5.3 Optimum process condition for enzymatic clarification of 113 white pitaya pulp
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LIST OF FIGURES
Figure Page 1.1 Scope of study 7
2.1 Pitaya tree 10
2.2 Pitaya flower 11
2.3 Pitaya fruit 11
2.4 Hylocereus polyrhizus 12
2.5 Hylocereus undatus 12
2.6 Seleicereus megalanthus 13
2.7 Flow chart of fruit juice production 17
2.8 Peeler for small and medium-sized fruits (Anonymous (e), 2007) 25
2.9 Peeler for large-sized fruits (Anonymous (f), 2007) 25
2.10 Process flow diagrams for three product development 26 Processes (after Ulrich and Eppinger, 2004)
2.11 Concept development phase 28
2.12 The five-step concept generation method 29 (after Ulrich and Eppinger, 2004)
2.13 Six-step process in concept selection process 30
2.14 Example of concept screening matrix 31
2.15 Example of concept scoring matrix 32
2.16 Standard process chart symbols 36
2.17 Flow chart of fruit juice production 37
3.1 Concept A 43
3.2 Concept B 43
3.3 Concept C 44
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3.4 Concept D 44
3.5 Concept E 45
3.6 Concept screening matrix 46
3.7 Concept scoring matrix 48
3.8 Final concept 49
3.8 Fruits grater and peeler 50
4.1 Steps for extraction and subsequent clarification 59 by enzymatic treatment of pitaya juice
4.2 Response surface for juice yield of red pitaya juice 65 (Pectinex Ultra SP-L) as a function of time and enzyme concentration at 40oC
4.3 Response surface for viscosity of red pitaya juice (Pectinex 66 Ultra SP-L) as a function of time and enzyme concentration at 40oC
4.4 Response surface for clarity of red pitaya juice 67 (Pectinex Ultra SP-L) as a function of time and enzyme concentration at 40oC
4.5 Response surface for L* value of red pitaya juice 68 (Pectinex Ultra SP-L) as a function of time and enzyme concentration at 40oC
4.6 Combined contour plot of red pitaya juice after enzymatic 69 treatment (Pectinex Ultra SP-L) as a function of enzyme concentration and incubation time at 40oC
4.7 Response surface for juice yield of white pitaya juice 74 (Pectinex Ultra SP-L) as a function of time and enzyme concentration at 40oC
4.8 Response surface for juice yield of white pitaya juice 75 (Pectinex CLEAR) as a function of time and enzyme concentration at 40oC
4.9 Response surface for viscosity of white pitaya juice 76 (Pectinex Ultra SP-L) as a function of time and enzyme concentration at 40oC 4.10 Response surface for viscosity of white pitaya juice (Pectinex 77 CLEAR) as a function of time and enzyme concentration
at 40oC
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4.11 Response surface for clarity of white pitaya juice (Pectinex 78 Ultra SP-L) as a function of time and enzyme concentration at 40oC 4.12 Response surface for clarity of white pitaya juice (Pectinex 79 CLEAR) as a function of time and enzyme concentration at 40oC 4.13 Response surface for L* value of white pitaya juice (Pectinex 80 Ultra SP-L) as a function of time and enzyme concentration at 40oC 4.14 Response surface for L* value of white pitaya juice (Pectinex 81 CLEAR) as a function of time and enzyme concentration at 40oC 4.15 Combined contour plot of white pitaya juice (Pectinex Ultra 82
SP-L) after enzymatic treatment as a function of enzyme concentration and incubation time at 49oC
4.16 Combined contour plot of white pitaya juice after enzymatic 82 treatment (Pectinex CLEAR) as a function of enzyme concentration and incubation time at 40oC
4.17 Difference in juice recovery using different instruments 85
4.18 Yield of red pitaya juice 92
4.19 Yield of white pitaya juice 93
4.20 Protein content of red pitaya juice 95
4.21 Protein content of white pitaya juice 95
4.22 Carbohydrate content of white pitaya juice 96
4.23 Phenolic content of red pitaya juice 99
4.24 Phenolic content of white pitaya juice 99
5.1 Operation process chart for pitaya juice production 104
5.2 Flow process chart for pitaya juice production 108
5.3 Process flow sheet of pitaya juice processing 110
5.4 Production scheme of pitaya juice 111
5.5 Material balance of red pitaya juice production 115
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5.6 Material balance of white pitaya juice production 117
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LIST OF ABBREVIATIONS
3D Three-dimensional
abs Absorbance value
b0 constant
b1 Linear coefficient of temperature
b2 Linear coefficient of enzyme concentration
b3 Linear coefficient of time
b12 Interaction coefficient of temperature and enzyme concentration
b13 Interaction coefficient of temperature and time
b23 Interaction coefficient of enzyme concentration and time
b11 Quadratic coefficient of temperature
b22 Quadratic coefficient of enzyme concentration
b33 Quadratic coefficient of time
cps Centipoise
HTST High-temperature-short-time
L* Lightness value
p Probability
RSM Response surface methodology
rpm Rotation per minute
R2 Regression coefficient
TSS Total soluble solids
X1 Coded level of maceration temperature
X2 Coded level of enzyme concentration
X3 Coded level of maceration time
y Response function
CHAPTER 1
INTRODUCTION
1.1 Fruit Juice Consumption
Juice is defined as the extractable fluid contents of cells or tissues (Merriam-
Webster, 2007). The manufacture of juices from fruits is as old as agriculture (Bates
et al., 2001). The demand for fruit beverages is largely based on their nutritive value,
flavour, aroma and colour. These quality factors are dependent directly on the
structure and chemical composition of the fresh fruit. The process starts with sound
fruit, freshly harvested from the field or taken from refrigerated or frozen storage
(McLellan and Padilla-Zakour, 2004). Fruits have always played an important role in
human nutrition (Horvath-Kerkai, 2006). Fruit juice is a source of vitamins, minerals,
carbohydrates, amino acids, flavanoids compounds and other unidentified
constituents. Due to the revolutionary development of technical equipment, the
appearance of chemicals, and biological substances (enzymes, clarifying and
flavouring agents), and the application of new technological procedures, especially
the aseptic technique – which enabled the production of fruit juices without
preservatives – of fruit juice production became widespread (Horvath-Kerkai, 2006).
Since fruit juices are caffeine-free, they are healthier for consumption than any other
caffeine-containing beverages. The global market for juice and juice products was
estimated to be about 50 billion litres in the late 1990s.
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1.2 Pitaya
The pitaya or dragon fruit is also known as pitahaya, strawberry pear, nanettikafruit,
thanh long or ‘kaktus madu’. It is a cactus species of the genus Hylocereus and
Stenocereus. Generally, pitaya comes in three types, which are Hylocereus undatus
(white flesh with pink skin), Hylocereus polyrhizus (red flesh with pink skin) and
Seleicereus megalanthus (white flesh with yellow skin) (Anonymous (d), 2007).
Pitaya originated in Mexico and Central America and subsequently, the plant has
been cultivated widely in countries such as Vietnam, Taiwan and Malaysia.
Pitaya is mildly sweet and low in calories, has attractive flesh and juicy with subtle
fruity flavour (melon-like flavour). Pitaya is round or oval; the skin is fuchsia-pink or
yellow depending on the species, leathery and slightly leafy; and the fruit usually
weighs about 200–1000g. It is rich in potassium, ferum, protein, fibre, sodium and
calcium which are good for human health. It also contains zinc, vitamin B1, vitamin
B2, vitamin B3, vitamin C, carotene and phosphorus. Pitaya can be converted into
juice, jam and red wine.
Recently, pitaya juice is becoming popular due to its nutritional benefits despite its
colourant properties. All the research done on pitaya (Hylocereus polyrhizus) focused
on the betalain contents. In the process of obtaining pitaya juice, the fruits were cut
in halves and the peels were removed manually (Herbach et al., 2006). Subsequently,
the fruit pulp was strained using a finisher. The strained pulp was centrifuged and the
supernatant juice was flushed with nitrogen and stored at -30oC until use. In the
research done by Moβhammer et al. (2005) to study the colour of fruit juice blends
3
from Opuntia and Hylocereus cacti, the process of obtaining pitaya juice was similar
as done by Herbach et al. (2006).
Currently this fruit utilization is further expanded to produce dragon fruit enzyme
and dragon fruit concentrated juice. These products are now available in the market.
This expansion has promoted dragon fruit as a great source of functional beverages.
However, less attention is being given to the appearance and texture of the drinking
products. The undesirable texture of the concentrated juice causes difficulties in
mixing the concentrate with water to be drunk. This situation may not attract the
consumers to buy this product again. Hence, action should be taken to overcome this
problem.
1.3 Enzymatic Clarification of Fruit Juice
Enzyme is an essential tool in juice processes, both in terms of quality improvement
and cost saving (Ramadan and Moersel, 2007). Fruit and vegetable juice production
is nowadays unthinkable without the use of enzymes (Baumann, 1981). The
degradation of plant cell walls by exogenous enzymatic treatment results in easier
release of the components contained in cells (Janser, 1997).
The cloudiness in the juice is mainly caused by the presence of polysaccharides such
as pectin and starch. The pectin can be associated with plant polymers and the cell
debris, which has a fibre-like molecular structure and makes the clarification process
harder. Enzyme-catalyzed breakdown of the plant cell-wall matrix and middle
lamella may first increase the immediate turbidity in the juice, which is generally
4
assumed to be mainly due to the presence of pectin and other fractions of fruit cell-
wall material (Grassin and Fauquembergue, 1996). Therefore, enzymatic treatment
by using pectinase is an effective way to reduce the pectin in the fruit juices because
pectinase has the ability to hydrolyze pectin and cause pectin–protein complexes to
flocculate (Rai et al., 2004; Lee et al., 2006; Liew Abdullah et al., 2007; Sin et al.,
2006), which could be easily removed by filtration. A complete enzymatic
breakdown of pectin is the key for producing clear and stable fruit juices. Though
hard to believe, juice clarification is the oldest and still largest market for
commercial pectinases (Baumann, 1981).
1.4 Fruit Processing Operation
The major unit operations in fruit processing are peeling, pulping, enzymation,
centrifugation, filtration, pasteurization, hot filling and cooling. Each step has its own
importance to the fruit processing operations. Fruit peeling has its own impact
towards the efficiency of the whole system.
In the processing of fruits, fruit peeler is needed to reduce the time required for
peeling process. It is crucial for the fruit processing industry to operate at minimal
operating costs. Peeling using hands is time consuming and may require several
workers to perform the operation, and thus may increase the operating costs.
Different types of fruits have different shapes and sizes. Thus, several different
machines are provided for separately processing each of the fruits. Therefore,
processing of a particular fruit, such as removing the skin from an orange, is usually