Development of good quality of yogurt in terms of texture, appearance, color, taste and ...

91 Pages·2017·1.61 MB·English

Development of good quality of yogurt in terms of
texture, appearance, color, taste and determination of
fat percentage in milk and yogurt

A DISSERTATON SUBMITTED TO THE BRAC UNIVERSITY FOR PARTIAL
FULFILLMENT OF THE REQUIREMENT FOR THE DEGREE OF BACHELOR OF
SCIENCE (B.Sc) IN MICROBIOLOGY

SUBMITTED BY
ANILA LABONNYA MODHU
STUDENT ID: 12126012
AUGUST, 2016

DEPARTMENT OF MATHEMATICS AND NATURAL SCIENCES
MICROBIOLOGY PROGRAM
BRAC UNIVERSITY
MOHAKHALI, DHAKA
DECLARATION

This is to declare that the research work embodying the results in this thesis entitled
“Development of good quality of yogurt in terms of texture, flavor, food value and low cost
and determining the fat percentage of milk and yogurt.” submitted by Anila Labonnya
Modhu, has been carried out by under the joint supervision and guidance of Professor Dr. M
Mahboob Hossain, Coordinator, Biotechnology and Microbiology Program, BRAC University in
partial fulfillment of B.Sc in Microbiology, at BRAC University, Dhaka. It is further declared
that the research work presented hereis original, has not been submitted anywhere else for any
degree or diploma.

Candidate

Anila Labonnya Modhu

Certified:

Prof. Dr. Mahboob Hossain
Associate Professor,
Microbiology program
Department of Mathematics and Natural Sciences
BRAC University
66, Mohakhali, Dhaka-1212
Bangladesh

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ACKNOWLEDGEMENTS

I am grateful to Professor A. A. Ziauddin Ahmad, Chairperson, Department of Mathematics
and Natural Sciences, BRAC University for allowing me and encouraging me to complete my
under graduate thesis. I would like to express my gratitude to Dr. Mahboob Hossain, my major
professor for his guidance and mentorship during this research project. I also thank him for his
constant support all throughout my student life and guiding me during the research work which
has enhanced my capability enormously. In addition, Iwould like to thank Ms. Shamima Akhtar
and Ms. Asma Afzal for guidance and encouragement in the lab.
I would like to express my eternal gratitude to my loving parents, for allthe love, patience, help
and support. I thank my brother, Vincent for his support.
I would like to thank specially, Ms. Mumu who was always there beside me in all of my thesis
works. Also for her support, critical comments and suggestions.My hearty gratitude to all my
thesis mates, for their friendship and support.
Special thanks to my family, for their support and prayers during this time. I willalways be
grateful for the constant love and encouragement they gave me along the way.
Most of all, I thank God for everything.

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ABSTRACT
In the present study efforts were made to develop improved quality of yogurt in terms of texture,
flavor, colour, taste and low fat content. To achieve this objective, better strains of Lactobacillus
were isolated from locally available well known branded yogurts of Dhaka city. It was done to
optimize the yogurt production with an improved quality yogurt. Total 40 samples were analyzed
by recombining many other samples. Of the forty yogurt samples, eight samples found to be of
better quality. Later on, from these eight samples two highest scored samples were selected. .
Observation of the quality assessment was done by hedonic scaling. Therefore, chemical,
physical, microbial and organoleptic analyses for samples were conducted at predetermined
days. Yeast and Lactobacillus spp was found from better samples. Also the fat content of milk
and yogurt showed that yogurt had higher fat content than milk which is healthier to eat. Starter
culture found from yogurt isolates may have potential to be used in dairy industries in terms of
their high technological and organoleptic characteristics.

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Table of Contents

Chapter Page
ABSTRACT……………………………………………………………….……………. 4
CONTENT……………………………………………………………………. ……… 5-6
LIST OF TABLES……………………………………………………………………... 7
LIST OF FIGURES………………………………………………………………….. 8-9
LIST OF ABBREVIATIONS……………….…………………………………….. 10-12
1.0 INTRODUCTION………………………………………………………………… 13
1.1 Yogurt……………………………………………………………………... 14
1.2 Biochemistry of yogurt……………………………………………………. 16
1.3 History of yogurt…………………………………………………………… 18
1.4 Different names of yogurt………………………………………………….. 19
1.5 Different types of yogurt…………………………………………………… 20
1.6 Health benefits of yogurt…………………………………………………… 23
1.7 Probiotics of yogurt…………………………………………………………. 25
1.8 Nutritional profile of yogurt………………………………………………… 26
1.9 Yogurt’s starter culture……………………………………………………… 29
1.10 Packaging materials of yogurt……………………………………………. 30
1.11 Aims and Objective………………………………………………………. 31

2.0 LITERATURE REVIEW………………………………………………………….. 32

3.0 MATERIALS AND METHOD…………………………………………………….. 39
3.1 Collection of market samples………………………………………………... 40
3.1.1 Milk……………………………………………………………………. 40
3.1.2 Starter yogurt…………………………………………………………… 41
3.1.3 Combination and labeling of different starter culture………………..… 41
3.2 Place of experiment…………………………………………………………. 41
3.3 Fermentation of yogurt………………………………………………………. 41
3.3.1 Ingredients for yogurt manufacture……………………………….. 42
3.3.2 Milk Standardization……………………………………………… 43
3.3.3 Homogenization…………………………………………………… 44
3.3.4 Heat treatment……………………………………………………... 44
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3.3.5 Inoculation and Fermentation……………………………………… 46
3.3.6 Cooling…………………………………………………………….. 46
3.4 Quality Assessment by Sensory & Organoleptic Evaluation or Physical
Test(Hedonic Scale)………………………………………………………. 47
3.5 Microbiological Test
3.5.1 Determination of the Bacterial Load
3.6.1a) Media Used………………………………………………….. 48
3.5.1 b) Techniques Employed………………………………………. 52
3.5.1 c) Enumeration of Bacterial Load……………………………… 52
3.5.1 d) Purification of the Isolates…………………………………... 53
3.5.2 Morphological and Cultural Studies of Selected Isolates…………… 53
3.5.3 Microscopic Observation or Characterization of the Isolates……….. 54
3.5.4 Maintenance & Preservation of the Isolates………………………… 55
3.6 Roese Gotlieb method……………………………………………………. 55-57
4. RESULTS……………………………………………………………………………. 58
4.1 Organoleptic Quality Assessment………………………………………………….... 59
a) First set of recombination:……………………………………………………... 59
b) Second set of recombination………………………………………………...… 64
4.1.1 A) Texture Acceptability……………………………………………………..…. 66
4.1.1 B) Appearance Acceptability………………………………………………...….. 67
4.1.1 C) Color Acceptability………………………………………………………….. 68
4.1.1 D) Taste Acceptability…………………………………………………………… 69
4.2 MICROBIAL ASSESMENT
4.2.1 Culture and Subculture……………………………………………...…….. 71
4.2.2 Gram Staining…………………………………………………………………….. 73
4.3 Final yogurt: Inoculated sample…………………………………………………… 73
4.4 Preservation of isolates…………………………………………………………….. 75
4.5 Chemical Analysis: percentage of fat of milk and yogurt…………………………. 76
5. DISCUSSION……………………………………………………………………...... 78-81
6. CONCLUSION……………………………………………………………………… 82-84
7. REFERENCES……………………………………………………………………… 85-87
APPENDICES…………………………………………………………………………. 88-91
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List of Tables

Contents Page
No.
Table 1.1: Yogurt and yogurt-like products originated in different regions of the world 19
Table 1.2: The composition of regular-, low-fat- and non-fat yogurt 21
Table1.3: Nutritional composition of different varieties of yogurt (per 100 g) 27
Table 3.1: Time-temperature combinations for milk pasteurization 45
Table3.2: Hedonic Scale 47
Table 4.1 : Name of recombined 32 samples of first screening 60
Table 4.2: Hedonic data of first set of yogurts 61
Table 4.3 Name of recombined 8 samples of screening 64
Table 4.4 Hedonic data of second set of yogurts 65
Table4.5: Microscopic observation from sample B and sample E isolates 74
Table4.6: Nutritional value of milk (full fat) 76
Table4.7: Nutritional value of yogurt 76

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List of Figures

Contents Page No.
Fig: 1.1: Lactose catabolism into glucose and galactose 16
Fig: 1.2: Embden-Meyerhof-Parnas pathway 17
Figure 3.1: Manufacturing process of set- and stirred-yogurt (Adapted from Lee 42
and Lucey, 2010)
Fig4.1: Sample-1 62
Fig4.2: Sample-2 62
Fig4.3:Sample-3 62
Fig4.4:Sample-4 62
Fig4.5: Sample-5 62
Fig4.6: Sample-6 62
Fig4.7: Sample-7 62
Fig4.8: Sample-8 62
Fig4.9: Sample-9 62
Fig4.10: Sample-10 62
Fig4.11: Sample-11 62
Fig4.12: Sample-12 62
Fig4.13: Sample-13 63
Fig4.14: Sample-14 63
Fig4.15: Sample-15 63
Fig4.16: Sample-16 63
Fig4.17: Sample-17 63
Fig4.18: Sample-18 63
Fig4.19: Sample-19 63
Fig4.20: Sample-20 63
Fig4.21: Sample-21 63
Fig4.22: Sample-22 63
Fig4.23: Sample-23 63
Fig4.24: Sample-24 63
Fig4.25: Sample-25 63
Fig4.26: Sample-26 63
Fig4.27: Sample-27 63
Fig4.28: Sample-28 63
Fig4.29: Sample-29 64
Fig4.30: Sample-30 64
Fig4.31: Sample-31 64
Fig4.32: Sample-32 64
Fig4.33: Sample A 65
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Contents Page No.
Fig4.34: Sample B 65
Fig4.35: Sample C 65
Fig4.36: Sample D 65
Fig4.37: Sample E 66
Fig4.38: Sample F 66
Fig4.39: Sample G 66
Fig4.40: Sample H 66
Fig 4.41: Mean of texture of second sets yogurts combination chart 67
Fig 4.42: Mean of appearance of second sets yogurts combination chart 68
Fig 4.43: Mean of color of second sets yogurts combination chart 69
Fig 4.44: Mean of taste of second sets yogurts combination chart 69
Fig 4.45: Average mean of quality of second sets yogurts combination chart 70
Fig 4.46 :Comparing Best two yogurts samples comparison in terms of texture, 71
appearance, color and taste chart
Fig4.47: Sample B on MRS media 72
Fig4.48: Sample B on NA 72
Fig4.49: Sample E on MRS media 72
Fig4.50: Sample E on NA 72
Fig4.51: Gram staining of Sample B 73
Fig4.52: Gram staining of Sample E 74
Fig4.53: yogurt from experimental LAB 75

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(LIST OF ABBREVIATIONS)
% percent
αalpha
βbeta
<less than
>more than
≤ less or equal to
≥more or equal to
ºCdegree celsius
ºFdegree fahrenheit
S/sec second
N normality
L/l litre
V volume
µg micro gram
µm micro meter
µl micro litre
cfu colony forming unit
cm centimeter
Conc.Concentration
Min/mins minute
e.g.as example
et.aland others
etcetcetra
Fig.figure
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