Effects of dried apple peel powder on the rheological and sensory properties of drinking yogurt

113 Pages·2017·2.41 MB·English

by  Zening Zhou

Effects of dried apple peel powder on the rheological and sensory
properties of drinking yogurt
By
Zening Zhou

A Thesis
Presented to
The University of Guelph

In partial fulfilment of requirements for the degree of
Master of Science
in
Food Science

Guelph, Ontario, Canada
© Zening Zhou, January, 2018
ABSTRACT
EFFECTS OF DRIED APPLE PEEL ON THE RHEOLOGICAL AND
SENSORY PROPERTIES OF DRINKING YOGURT

Zening Zhou Advisor:
University of Guelph, 2018 Dr. Gisèle LaPointe

The study was undertaken to investigate the effect of commercial dried apple peel powder
(CDAP) and Granny Smith dried apple peel powder (GSAP) addition on the rheological and
sensory properties of drinking yogurt in order to develop a dietary fiber enriched drinking yogurt.
The rheological study showed that drinking yogurt fortified with 3.2% CDAP and 4.0% GSAP
were the best-fortified amounts for drinking yogurt with the same viscosity (50-s) and were further
used to sensory evaluation. Consumer acceptance of drinking yogurt was evaluated using a 9-point
consumer liking scale and a 5-point Just-About-Right scale. Consumers found that the 4.0% GSAP
fortified drinking yogurt was acceptable while 3.2% CDAP fortified drinking yogurt was not
accepted by consumers due to too dark color and grainy texture. These results suggest the
possibility of utilizing dried apple peel powder as a dietary fiber enriched ingredient in drinking
yogurt manufacture.
ACKWONLEDGEMENT
I would like to show my gratitude to my advisor Dr. LaPointe. Thank you for your support,
inspiration and guidance. Thank you for always willing to spend time with me and being patient
with me. The master’s learning process would not have been possible without your knowledge,
advice, and experience. I would like to also thank my Dr. Duizer. You opened up a new door to
the world of sensory science for me and made me fall in love with this field of research. Thank
you for your trust in me. You gave me more confidence and encouraged me to problem solve. You
inspired me to take on a positive attitude in the face of difficult situations. I really enjoyed working
in the food formulation lab. It is a really nice place to explore food products.

I would like to extend my thanks to all the members in Dr. LaPointe’s group. Thank you for sharing
your opinions about my project and help me to improve my presentation skills. I enjoyed every
lab meeting we had together. I feel so happy to have worked with all of you.

I also would like to thank Nicole, Peter, and James. Thank you for bringing me your happiness
and encourage, especially, thank you for helping me to improve my writing. I would especially
like to thank Yi, for your love, support and help. You helped me gain confidence and belief in
myself and allowed me to think that everything is possible.

Lastly, a big thanks to my parents. Your unconditional love has helped me face all the challenges.
Thank you for your spiritual and financial support which has helped me throughout my education
abroad. Thank you for always being there whenever I need. I wish I could do more for you.

iii
TABLE OF CONTENTS
ABSTRACT ................................................................................................................................... ii
ACKWONLEDGEMENT ........................................................................................................... iii
TABLE OF CONTENTS ............................................................................................................ iv
LIST OF TABLES ...................................................................................................................... vii
LIST OF FIGURES ................................................................................................................... viii
LIST OF ABBREVIATIONS ..................................................................................................... ix
CHAPTER 1: INTRODUCTION ................................................................................................ 1
CHAPTER 2: LITERATURE REVIEW.................................................................................... 4
2.1 Yogurt ................................................................................................................................................. 4
2.1.1 Yogurt introduction ...................................................................................................................... 4
2.1.2 Drinking yogurt ............................................................................................................................ 4
2.1.3 Yogurt nutritional value ............................................................................................................... 6
2.1.4 Fortified yogurt ............................................................................................................................ 7
2.2 Sensory evaluation ........................................................................................................................... 10
2.2.1 Consumer acceptance test .......................................................................................................... 10
2.2.2 Just-About-Right ........................................................................................................................ 11
2.3 Dietary fiber ..................................................................................................................................... 12
2.4 Apple by-products ........................................................................................................................... 14
2.4.1 Apple by-products introduction ................................................................................................. 14
2.4.2 Apple by-products nutritional value .......................................................................................... 15
2.4.3 Functional properties of apple peels .......................................................................................... 17
2.4.4 Apple by-products application in food manufacture.................................................................. 19
iv
CHAPTER 3: EFFECTS OF DRIED APPLE PEEL POWDER ON THE
RHEOLOGICAL PROPERTIES OF DRINKING YOGURT .............................................. 21
3.1 Introduction ..................................................................................................................................... 21
3.2 Materials and Methods ................................................................................................................... 22
3.2.1 Dried apple peel powder development....................................................................................... 22
3.2.3 Determining the proximate composition of dried apple peel powder ........................................ 23
3.2.4 Functional properties of dried apple peel powders .................................................................... 27
3.2.5 Drinking yogurt development .................................................................................................... 29
3.2.6 Yogurt manufacture parameters evaluation ............................................................................... 31
3.2.7 Rheological properties of yogurt................................................................................................ 34
3.2.8 Final drinking yogurt formulation selection .............................................................................. 35
3.2.9 Statistic analysis ......................................................................................................................... 35
3.3 Results............................................................................................................................................... 36
3.3.1 Proximate compounds analysis of dried apple peel powder ...................................................... 36
3.3.2 Functional properties of dried apple peel powders .................................................................... 37
3.3.3 Viscosity of yogurt ..................................................................................................................... 38
3.3.4 Final drinking yogurt formulation selection .............................................................................. 41
3.3.6 Drinking yogurt manufacture parameters .................................................................................. 41
3.3.7 Color of drinking yogurt ............................................................................................................ 43
3.3.8 Viscoelastic properties of drinking yogurt ................................................................................. 45
3.4 Discussion ......................................................................................................................................... 49
3.4.1 Dried apple peel powder ............................................................................................................ 49
3.4.2 Manufacture parameters of fortified drinking yogurt ................................................................ 53
3.4.3 Rheological properties of drinking Yogurt ................................................................................ 54
3.5 Conclusion ........................................................................................................................................ 57
v
CHAPTER 4: EFFECTS OF DRIED APPLE PEEL POWDERS ON SENSORY
PROPERTIES OF DRINKING YOGURT .............................................................................. 60
4.1 Introduction ..................................................................................................................................... 60
4.2 Material and Methods ..................................................................................................................... 61
4.2.1 Materials..................................................................................................................................... 61
4.2.2 Sample preparation .................................................................................................................... 61
4.2.3 Panelist Recruitment .................................................................................................................. 62
4.2.4 Procedure ................................................................................................................................... 62
4.2.5 Statistic analysis ......................................................................................................................... 63
4.3 Results............................................................................................................................................... 64
4.3.1 Consumer liking test .................................................................................................................. 64
4.3.2 Just-About-Right ........................................................................................................................ 65
4.4 Discussion ......................................................................................................................................... 76
4.4.1 Consumer liking ......................................................................................................................... 76
4.4.2 Just-About-Right ........................................................................................................................ 78
4.5 Conclusion ........................................................................................................................................ 80
CHAPTER 5: CONCLUSION AND FUTURE WORK ......................................................... 82
References:................................................................................................................................... 85
Appendix A .................................................................................................................................. 97
Appendix B .................................................................................................................................. 98
Appendix C ................................................................................................................................ 101
Appendix D ................................................................................................................................ 103
Appendix E ................................................................................................................................ 104
vi
LIST OF TABLES
Table 3.1: Formulation of drinking yogurt with 50% yogurt ...................................................................................... 32
Table 3.2: Formulation of drinking yogurt with 60% yogurt ...................................................................................... 32
Table 3.3: Formulation of drinking yogurt with 70% yogurt ...................................................................................... 32
Table 3.4: Proximate components of dried apple peel powder ................................................................................... 37
Table 3.5: Functional properties of apple peel powder .............................................................................................. 38
Table 3.6: Flow behavior of 70% yogurt containing different concentration of GSAP & CDAP at different level .. 39
Table 3.7: Flow behavior of 60% yogurt containing different concentration of GSAP & CDAP at different level .. 40
Table 3.8: Flow behavior of 50% yogurt containing different concentration of GSAP & CDAP at different level .. 40
Table 3.9: Calculated total solid content and calculated dietary fiber content of drinking yogurt ............................. 41
Table 3.10: pH, titratable acidity, water holding capacity and serum separation of drinking yogurt (means ± SD) .. 42
Table 3.11: Color parameters of drinking yogurt (means ± SD) ................................................................................. 43
Table 3.12: Average of parameters obtained by strain sweep (0.1-1000% strain at 1 Hz, 4 ℃) of drinking yogurt
fortified with different concertation dried apple peel powder ............................................................................ 47
Table 3.13: Yield point and flow point of drinking yogurt generated from stress sweep (Mean ± SD) ..................... 48
Table 4.1: Formulation of 3 samples for sensory evaluation ...................................................................................... 61
Table 4.2: Summary of mean liking score of appearance, texture, flavor and overall liking of all drinking yogurt
samples (HSD) ........................................................................................................................................... 64
Table 4.3: Dietary fiber content and the viscosity value of drinking yogurt ............................................................... 64
Table 4.4: Summary of mean score of colour, thickness, apple flavor, sourness and sweetness (one-sample t-test). 67
Table 4.5: Data for penalty analysis of control sample and mean drop ...................................................................... 73
Table 4.6: Data for penalty analysis of GS40 and mean drop ..................................................................................... 74
Table 4.7: Data for penalty analysis of CD32 and mean drop .................................................................................... 75

vii
LIST OF FIGURES
Figure 2.1： Fruit/flavored yogurt manufacture ........................................................................................................... 5
Figure 2.2: A 9-point scale question sample in consumer acceptance/liking questionnaire of consumer acceptance
test. ............................................................................................................................................................. 11
Figure 2.3: A Just-About-Right scale and question sample in consumer acceptance/liking questionnaire of consumer
acceptance test............................................................................................................................................ 11
Figure 3.1: Drinking yogurt manufacture procedure .................................................................................................. 30
Figure 3.2: Granny Smith apple peel powder (left) and commercial dried apple peel powder (right) ....................... 36
Figure 3.3: Effects of dried apple peel powders on pH, titratable acidity, water holding capacity and serum separation
of drinking yogurt (means ± SD) ............................................................................................................... 43
Figure 3.4: Effect of dried apple peel powder on the color of drinking yogurt (means ± SD) ................................... 44
Figure 3.5: Representative plot of storage modulus G’ & G’’ loss modulus versus shear strain of drinkable yogurt
containing different dried apple peel powder concentration at 4 ℃. ......................................................... 46
Figure 3.6: Example of representative plot of storage modulus G’ & G’’ versus shear stress of drinkable yogurt
containing different dried apple peel powder concentration at 4 ℃. ......................................................... 47
Figure 3.7: Yield point and flow point of drinking yogurt generated from stress sweep (Mean ± SD) ..................... 49
Figure 4.1: Frequency of JAR 5 levels scale of control .............................................................................................. 66
Figure 4.2: Frequency of JAR 5 levels scale of GS40 ................................................................................................ 66
Figure 4.3: Frequency of JAR 5 levels scale of CD32 ................................................................................................ 66
Figure 4.4: Consumer panel percentage of the JAR 1, 3, 5 level for control .............................................................. 69
Figure 4.5: Consumer panel percentage the JAR 1, 3, 5 level for GS40 .................................................................... 69
Figure 4.6: Consumer panel percentage the JAR 1, 3, 5 level for CD32 .................................................................... 70

viii
LIST OF ABBREVIATIONS
GSAP …………………………………………………………Granny Smith apple peel powder
CDAP …………………………………………………… Commercial dried apple peel powder
WHC ……………………………………………………………………Water holding capacity
OHC ………………………………………………………………………..Oil holding capacity
SC …………………………………………………………………………….Swelling capacity
LVR ………………………………………………………………...Linear Viscoelastic Region
JAR ……………………………………………………………………………Just-About-Right
GAE……………………………………………………………………….Garlic Acid Equivalents
TE……………………………………………………………………….………Trolox equivalents

ix
CHAPTER 1: INTRODUCTION
Yogurt is one of many types of fermented milk products, and is the result of inoculated milk
mixed with a starter culture consisting of Str. thermophiles and Lb. delbrueckii spp. Bulgaricus
(Tamime & Robinson, 2007). It is a well-known high nutritional value dairy product that contains
active cultures. For this reason, yogurt is consumed widely around the world (Tamime &
Robinson, 2007). With the development of yogurt production, yogurt varieties have increased to
include fruit yogurt to meet consumers’ requirements. Drinking yogurts are a popular flavored
yogurt product and are produced by diluting yogurt or fermenting diluted milk and adding fruit
syrup or fruit puree (Chandan & Kilara, 2013). Lack of viscosity and syneresis are the two main
challenges facing the drinking yogurt industry in the technical aspect.
Fruit by-products are regarded as dietary fiber and bioactive compounds enrichment ingredients.
Many previous studies have utilized fruit by-products into yogurt manufacturing (Espírito Santo
et al., 2013; García-Pérez et al., 2005; Issar, Sharma, & Gupta, 2017; Sah et al., 2016; Sendra et
al., 2010; Staffolo et al., 2004;). Fruit by-product fortification has been shown to increase the
nutritional value of yogurt, especially dietary fiber. Previous studies showed that soluble dietary
fiber could increase the viscosity of foods and insoluble fibers have high porosity and low density
(Elleuch et al., 2011). O'Shea, Arendt, & Gallagher (2012) have also reported that the soluble and
insoluble fiber can change the water binding abilities, gelling properties of yogurt. Oven dried
passion fruit pulp powder applied to probiotic yogurts has been shown to enhance the apparent
viscosity and structure of yogurt (Espírito Santo et al., 2013). Fortified foods with additional
dietary fiber ingredient have been approved to render the texture quality (Stokes et al., 2013).
However, fruit by-product powders also affect the quality and sensory properties of yogurt due
to particle size and dosage of the addition. Sendra et al. (2010) have found the particle size and
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