UNIVERSITI PUTRA MALAYSIA · 2018-04-09 · Sifat kanji sagu telah dikaji-selidik melalui...
Transcript of UNIVERSITI PUTRA MALAYSIA · 2018-04-09 · Sifat kanji sagu telah dikaji-selidik melalui...
UNIVERSITI PUTRA MALAYSIA
TENG LI YUEN
FK 2011 124
TEXTURAL AND RHEOLOGICAL CHARACTERISATIONS OF SAGO STARCH AND SAGO STARCH SUGAR GELS
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TEXTURAL AND RHEOLOGICAL CHARACTERISATIONS OF SAGO
STARCH AND SAGO STARCH SUGAR GELS
By
TENG LI YUEN
Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia,
in Fulfilment of the Requirements for the Degree of Master of Science
September 2011
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Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfilment
of the requirement for the degree of Master of Science
TEXTURAL AND RHEOLOGICAL CHARACTERISATIONS OF SAGO
STARCH AND SAGO STARCH SUGAR GELS
By
TENG LI YUEN
September 2011
Chair : Assoc. Prof. Ir. Chin Nyuk Ling, PhD
Faculty : Faculty of Engineering
The behaviour of native sago starch was investigated through characterisation,
rheological and textural measurements in finding its use as a gelling agent in frozen-
baked products. The effects of sago starch (6-8%), sugar (25-35%), and shearing
speed of mixer (20-50 rpm) on rheological and textural characteristics of gel were
investigated by means of response surface methodology. Increase in sago starch and
sugar levels both increased (P < 0.01) gel stiffness. Higher shearing speeds reduced
(P < 0.05) gel stiffness due to a decrease in starch swelling and an increase in starch
breakdown during cooking.
The values of the experimental variables which minimised and maximised the
textural parameters of hardness, gumminess, resilience, cohesiveness, and
springiness were estimated by means of ridge analysis to determine the processing
conditions at which these extremes can be reached. The maximum gel cohesiveness
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brought by the processing variables was set as the criterion to obtain optimum
formulation and processing of sago-starch based gels.
Utilising the optimised formulation and processing condition for gel setting, the
pasting behaviour, rheological and textural characteristics of sago starch-sugar gels
were compared with those of corn, wheat, tapioca, and potato starches. The
morphological and thermal properties of these starches were investigated via
scanning electron microscopy and differential scanning calorimetry respectively.
High-amylose cereal starches (wheat and corn) produced harder gels (hardness =
225.1–248.0 g), while low-amylose root starch (tapioca) produced softer gels
(hardness = 4.9 g). Sago and potato starches produced gels with high cohesiveness
(0.90–0.94), indicating good setting of gels.
The effect of freezing and thawing on rheological and textural characteristics of gels
were investigated. The freezing and thawing processes greatly increased the
viscoelasticity and hardness of sago starch-sugar gels. These negative effects were
significantly reduced by reheating the freeze-thawed gels at high temperature (80 °C).
The freeze-thaw stability of various starch gels were investigated by gravimetric
measurements of the water of syneresis after three freeze-thaw cycles. Sago starch
produced gels with relatively low syneresis (3.23%) compared with corn (15.5%)
and wheat (4.26%) starches. The high cohesiveness and low syneresis of sago starch-
sugar gels, and their ability to recover from structural changes caused by freezing
and thawing, implied potential use of sago starch as a gelling agent in frozen-baked
products.
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Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai
memenuhi keperluan untuk ijazah Master Sains
TEKSTUR DAN SIFAT REOLOGI KANJI SAGU DAN GEL SAGU GULA
Oleh
TENG LI YUEN
September 2011
Pengerusi : Prof. Madya Ir. Chin Nyuk Ling, PhD
Fakulti : Fakulti Kejuruteraan
Sifat kanji sagu telah dikaji-selidik melalui pengukuran reologi dan tekstur untuk
memperluaskan penggunaannya sebagai ejen gel dalam produk bakeri sejukbeku.
Pengaruh kanji sagu (6-8%), gula (25-35%) dan kelajuan putaran pengaduk (20-50
rpm) pada sifat-sifat reologi and tekstur gel telah diselidik dengan menggunakan
kaedah permukaan tindakbalas (response surface methodology). Peningkatan
kepekatan kanji sagu and gula didapati meningkatkan (P < 0.01) keteguhan gel.
Kelajuan putaran pengaduk mengurangkan (P < 0.05) keteguhan gel sebab kadar
pembengkakan granul kanji telah berkurang manakala kadar pemecahan granul telah
meningkat dalam proses memasak.
Nilai-nilai pembolehubah eksperimen yang meminimalkan serta memaksimumkan
parameter tekstur kekerasan, kebergetahan, ketahanan, kepaduan dan kekenyalan gel
telah dianggar melalui analisis bubungan (ridge analysis) untuk menentukan keadaan
pemprosesan di mana ekstrim-ekstrim parameter tersebut boleh diperoleh. Kepaduan
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gel maksimum telah ditetapkan sebagai kriteria untuk mendapatkan formulasi dan
keadaan pemprosesan bagi menghasilkan gel kanji sagu yang optimum.
Dengan menggunakan rumusan dan keadaan pemprosesan bagi penghasilan gel yang
optimum, sifat pempasturan serta ciri-ciri reologi dan tekstur gel sagu telah
diperbanding dengan gel kanji jagung, gandum, ubi kayu dan ubi kentang. Sifat
morfologi and sifat termal kanji ini juga telah dikaji dengan menggunakan
mikroskop penskanan elektron dan kalorimetri penskanan pembezaan. Kanji bijirin
(gandum dan jagung) yang tinggi dengan amilosa menghasilkan gel yang lebih keras
(kekerasan = 225.1–248.0 g), manakala kanji ubi kayu menghasilkan gel yang lebih
lembut (kekerasan = 4.9 g). Kanji sagu dan kanji ubi kentang menghasilkan gel yang
berkepaduan tinggi (0.90-0.94). Ini merupakan satu ciri gel yang sempurna.
Pengaruh pembekuan dan penyahbekuan pada sifat reologi dan tekstur gel telah
dikaji-selidik. Proses pembekuan dan penyahbekuan telah meningkatkan viskoelastis
dan kekerasan gel sagu dengan ketara. Kesan negatif ini dapat dikurangkan dengan
memanaskan gel pada suhu yang tinggi (80 °C). Kestabilan sejukbeku-nyahbeku gel
kanji telah dikaji melalui penyukatan air sineresis selepas tiga kitaran sejukbeku-
nyahbeku. Gel kanji sagu menunjukkan tahap sineresis yang rendah (3.23%)
berbanding dengan gel kanji jagung (15.5%) dan kanji gandum (4.26%). Nilai
kepaduan gel yang tinggi dan tahap sineresis yang rendah, serta keupayaan gel sagu
untuk memulih daripada perubahan struktur akibat proses sejukbeku-nyahbeku
ternyata potensi kanji sagu untuk digunakan sebagai ejen gel dalam produk bakeri
sejukbeku.
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ACKNOWLEDGEMENTS
My deepest gratitude to Dr. Chin Nyuk Ling, whose combination of intellect,
creativity, and patience were invaluable to the final fruition of my work. I wish to
thank Dr. Yus Aniza Yusof for her valuable comments and advice throughout my
time in research. I would like to acknowledge the editors and reviewers of Food
Hydrocolloids and Carbohydrate Polymers who critically analysed and took great
interest in my work. I am also grateful to my late professor, Dr. Kassim A. Abbas,
for his inspiring lectures. May peace be with him forever.
For the completion of my experimental work, I would like to thank the following
people for their helping hands and invaluable assistance: Andy for the modification
and set-up of the jacketed mixer; Dr. Siti Mazlina and Soh Jo Yong for providing the
sago starch; Dr. Abel Gaspar-Rosas, Chua Sheng Keong, Jasmine Ooi, and Josh Lai
from Research Instruments Sdn. Bhd., for their guidance and expertise in rheometry;
Tracy Ng from Lee Hung Scientific Sdn. Bhd. for her guidance and help with the
Texture Analyser; Kobra for her guidance in differential scanning calorimetry; Dr.
Tey Beng Ti, Chew Few Ne, Adli Nazri, and Ismail of Department of Chemical and
Environmental Engineering, for their help with centrifugations and scanning electron
microscopy; and all the departmental laboratory staffs, for their help and support.
My love and thanks to my colleagues for their thoughtful comments, suggestions,
and support, and to my family and friends for their continued patience,
understanding, and love. From the bottom of my heart, thank you, for everything.
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I certify that a Thesis Examination Committee has met on 6 September 2011 to
conduct the final examination of Teng Li Yuen on his thesis entitled “Textural and
Rheological Characterisations of Sago Starch and Sago Starch Sugar Gels” 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:
Farah Saleena binti Taip, PhD
Senior Lecturer
Faculty of Engineering
Universiti Putra Malaysia
(Chairman)
Rosnah binti Shamsudin, PhD
Senior Lecturer
Faculty of Engineering
Universiti Putra Malaysia
(Internal Examiner)
Siti Mazlina binti Mustapa Kamal, PhD
Associate Professor
Faculty of Engineering
Universiti Putra Malaysia
(Internal Examiner)
Norziah Mohd Hani, PhD
Professor
School of Industrial Technology
Universiti Sains Malaysia
(External Examiner)
________________________
SEOW HENG FONG, PhD
Professor and Deputy Dean
School of Graduate Studies
Universiti Putra Malaysia
Date: 20 December 2011
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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:
Chin Nyuk Ling, PhD, Ir
Associate Professor
Faculty of Engineering
Universiti Putra Malaysia
(Chairperson)
Yus Aniza Yusof, PhD
Associate Professor
Faculty of Engineering
Universiti Putra Malaysia
(Member)
_________________________________
BUJANG BIN KIM HUAT, PhD
Professor and Dean
School of Graduate Studies
Universiti Putra Malaysia
Date:
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DECLARATION
I declare that the thesis is my original work except for quotations and citations which
have been duly acknowledged. I also declare that it has not been previously, and is
not concurrently, submitted for any other degree at Universiti Putra Malaysia or at
any other institution.
_______________________
TENG LI YUEN
Date: 6 September 2011
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TABLE OF CONTENTS
Page
ABSTRACT ii
ABSTRAK iv
ACKNOWLEDGEMENTS vi
APPROVAL vii
DECLARATION ix
LIST OF TABLES xii
LIST OF FIGURES xiii
LIST OF ABBREVIATIONS xvi
CHAPTER
1 INTRODUCTION 1
1.1 Research Background 1
1.2 An Introduction to Sago Starch 3
1.3 Objectives of This Research 4
2 LITERATURE REVIEW 6
2.1 Introduction 6
2.2 Composition and Structure of Starch 7
2.2.1 Molecular Composition: Amylose and Amylopectin 8
2.2.2 Microscopic Structure 10
2.2.3 Macroscopic Organisation 11
2.3 Functional Properties of Starch 12
2.3.1 Gelatinisation 13
2.3.2 Pasting 13
2.3.3 Retrogradation 14
2.4 Methods and Measuring Techniques 15
2.4.1 Measuring Gelatinisation and Retrogradation Properties 15
2.4.2 Measuring Pasting Properties 17
2.4.3 Measuring Gel Viscoelasticity 19
2.4.4 Measuring Gel Texture 20
2.4.5 Measuring Freeze-thaw Stability of Gel 22
2.5 Factors Affecting Behaviours of Starch Gel 23
2.5.1 Compositional Factors 23
2.5.2 Processing Factors 26
2.6 Physico-Chemical and Rheological Studies on Sago Starch 27
2.7 Applications of Sago Starch 29
2.8 Summary 31
3 MATERIALS AND METHODS 32
3.1 Introduction 32
3.2 Materials 32
3.2.1 Starch 32
3.2.2 Sugar and Water 33
3.2.3 Jacketed Mixer 34
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3.3 Rheological and Textural Characterisation of Gels 35
3.3.1 Gel Preparations 35
3.3.2 Oscillatory Rheometry Measurements 37
3.3.3 Texture Profile Analysis 40
3.3.4 Starch Pasting Measurements 43
3.3.5 Syneresis Measurements 45
3.3.6 Microstructure of Gel 46
3.4 Native Starch Analysis 48
3.4.1 Morphological Analysis 48
3.4.2 Thermal Analysis 48
3.5 Experimental Design and Statistical Analysis 51
3.5.1 Response Surface Methodology 52
3.5.2 Ridge Analysis and Optimisation of Sago Starch-Sugar Gel 54
3.5.3 Comparison of Starches 55
4 RESULTS AND DISCUSSION 58
4.1 Introduction 58
4.2 Characterisation of Sago Starch-Sugar Gel 59
4.2.1 Gel Preparations and Experimental Design 59
4.2.2 Rheological Behaviour of Gels 60
4.2.3 Textural Characteristics of Gels 66
4.3 Optimisation of Sago Starch-Sugar Gel 75
4.4 Analysing Starch Structure 76
4.4.1 Morphological Properties 77
4.4.2 Gelatinisation and Retrogradation Properties 79
4.5 Effect of Starch Source 82
4.5.1 Gel Preparations 82
4.5.2 Pasting Properties 83
4.5.3 Viscoelastic Properties 86
4.5.4 Textural Properties 87
4.5.5 Pearson Correlation 88
4.6 Effect of Freezing, Thawing and Reheating on Stability of Gels 90
4.6.1 Gel Preparations 90
4.6.2 Viscoelastic Properties 90
4.6.3 Textural Properties 93
4.6.4 Syneresis 96
4.6.5 Microstructure of Gels 98
5 SUMMARY, CONCLUSION AND
RECOMMENDATIONS FOR FUTURE RESEARCH 100
5.1 Summary and Conclusion 100
5.2 Recommendations for Future Work 102
REFERENCES/BIBLIOGRAPHY 104
APPENDICES 110
BIODATA OF STUDENT 127
LIST OF PUBLICATIONS 128