ABSTRACT
Optimization of isolation and performance evaluation of Saccharomyces cerevisiae from palm wine at different proofing time during bread production was investigated using response surface methodology and central composite design. Yeast quantity (X1), proofing time (X2) and improver quantity (X3) were the independent variables considered, while bread production was the response variable. Results showed that X1, X2 and X3 had a significant effect on the bread runs (P<0.05). The correlation coefficient of 11.485, 12.539, 9.273937, 10.14511, 10.729, 6.523, 11.000, 7.297 and 5.158 observed between the predicted and actual values for the response variables are evidence that that the regression model can represent the experimental data well. The coefficient of determination, R2 of most of the response variables were higher than 0.8. Based on the response surface and superimposed plots, the selected optimal formulation of bread production with desired sensory quality was observed by incorporating with 4.78g of X1, 40mins of X2 and 1.02g of X3. The result of this study showed that Saccharomyces cerevisiae from palm wine can be used to produce bread in the food industry.
TABLE OF CONTENTS
Title
Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgement v
Table
of Contents vi
List
of Figures ix
List
of Tables x
List
of Plates xi
Abstract xii
CHAPTER 1
1.0 INTRODUCTION 1
1.1 Statement of Problem 2
1.2 Justification of the study 2
1.3 Aim and objectives 2
CHAPTER 2: LITERATURE
REVIEW
2.1 Yeast 3
2.1.1 History of Yeast 3
2.1.2 Nutritional and Growth of Yeast 4
2.1.3 Ecology of Yeast 5
2.1.4 Reproduction of Yeast 6
2.1.5 Uses of Yeast 6
2.1.6 Baker’s Yeast 9
2.2 Bread Production 10
2.2.1 Ingredients of bread 11
2.2.2 Bread Making Process 12
2.2.3 Processing Stages 13
2.3 Palm Wine 19
CHAPTER
3: MATERIALS AND METHODS
3.1 Sample collection 22
3.2 Yeast generation (baker’s seed
generation) and characterization 22
3.2.1 Viability Test 22
3.3 Experimental design 23
3.4 Determination of Fermentative ability
of the yeasts 26
3.5 Proximate Analysis of Bread Samples 26
3.5.1 Determination of Moisture Content 26
3.5.2 Determination of Crude Protein 27
3.5.3 Determination of Fat Content 28
3.5.4 Crude Fibre determination 29
3.5.5 Ash determination 29
3.6 Determination of Physical Properties
of Bread Loaves 31
3.6.1 Determination of bread weight 31
3.6.2 Determination of loaf volume 31
3.6.3 Determination of specific volume 31
3.6.4 Determination of oven spring 31
3.7 Sensory evaluation 31
3.8 Analysis of data 32
CHAPTER
4: RESULTS AND DISCUSSION
4.1 Determination of the Fermentative
Ability of the Yeast Extract 33
4.2 Physical Properties of Bread Leavened
with Yeast 33
4.2.1 Loaf Weight 36
4.2.2 Loaf Volume 40
4.2.3 Specific Volume 43
4.2.4 Oven Spring 46
4.3 Proximate Composition of Bread
Leavened with Yeast Extracted from Palm Wine 49
4.3.1 Moisture Content 51
4.3.1 Protein Content 54
4.3.3 Fat Content 57
4.3.4 Crude Fibre 60
4.3.5 Ash Content 63
4.4 Sensory properties of bread leavened
with yeast extracted from palm wine 66
4.4.1 Crust Appearance 66
4.4.2 Crumb Appearance 70
4.4.3 Taste 72
4.4.4 Aroma 75
4.4.5. Crumb Texture 78
4.4.6 Softness of Feel 80
4.4.7 Mouth Feel 83
4.4.7 Optimization 85
CHAPTER
5: CONCLUSION AND RECOMMENDATIONS
5.1 Conclusion 88
5.2 Recommendation 88
References 89
Appendix
LIST OF FIGURES
3.1: Flow Chart of Brand Production
4.2: Effects of yeast and improver on the taste of
bread leavened with yeast extracted from Palm wine
LIST OF TABLES
Table
3.1: Coded factor settings of central composite design for performance
evaluation of
Saccharomyces cerevisiae extracted from palm wine
Table
3.2: Actual settings of central composite design for performance evaluation of
Saccharomyces cerevisiae extracted from palm wine
Table
4.1: Fermentative Ability of Saccharomyces
cerevisia extracted from palm wine
Table
4.2: Physical Properties of Bread leavened with yeast extracted from palm wine
Table
4.3: Analysis of variance for response surface quadratic model for loaf weight
Table
4.4: Analysis of variance for response surface quadratic model for loaf volume
Table
4.5: Analysis of variance for response surface linear model for specific volume
Table
4.6: Analysis of variance for response surface linear model for oven spring
Table
4.7: Proximate Composition of Bread leavened with yeast isolated from palm wine
Table
4.8: Analysis of variance for response surface quadratic model for moisture
content
Table
4.9: Analysis of variance for response surface quadratic model for protein
content
Table
4.10: Analysis of variance for response surface quadratic model for fat content
Table
4.11: Analysis of variance for response surface quadratic model for crude fibre
content
Table
4.12: Analysis of variance for response surface quadratic model for ash content
Table
4.13: Sensory Properties of Bread leavened with yeast isolated from palm wine
Table
4.14: Analysis of variance for response surface quadratic model for crust
appearance
Table
4.15: Analysis of variance for response surface quadratic model crumb
appearance
Table
4.16: Analysis of variance for response quadratic model for taste
Table
4.17: Analysis of variance for response quadratic model for aroma
Table
4.18: Analysis of variance for response quadratic model for crumb texture
Table
4.19: Analysis of variance for response surface quadratic model for softness of
feel
Table
4.20: Analysis of variance for response surface quadratic model for mouth feel
Table
4.21: Optimization criteria for bread leavened with yeast isolated from palm
wine
Table
4.22: Optimization results for bread leavened with yeast extracted from palm
wine
LIST OF PLATES
4.1:
Bread Samples
CHAPTER 1
INTRODUCTION
1.1
BACKGROUND OF STUDY
Palm wine is an alcoholic beverage
produced by spontaneous fermentation of the sap of palm trees (Dayo-Owoyemi et al., 2008). The sap is originally
sweet and serves as a rich substrate for growth of various types of microorganisms
(Ogbulie et al., 2007). Fermentation
of palm wine starts soon after the sap is collected and within an hour or two,
it becomes reasonably high in alcohol (up to 40%). If it is allowed to continue
to ferment for more than a day, it starts turning into vinegar(Ogbulie et al., 2007). It’s reported that yeast
and bacteria originate from the gourd, palm trees and tapping implements.
However, the high sugar content of the juice would seem to selectively favor
the growth of yeasts which might originate from the air. This is reported by
the fact that fermentation also takes place in plastics containers. Within
24hours, the initial pH is reduced from 7.46-6.8 to 5.5 and the alcoholic
content ranges from 1.5-2.1%. The organic acids present are lactic acid, acetic
acid and tartaric acid (Uzogara et al,
1990). Although, palm wine may be presented in variety of flavours, ranging
from sweet (unfermented) to sour (fermented) and vinegary, it is mostly enjoyed
by people when sweet (Elijah et al.,
2010).
Generally, palm has
several nutritional, medicinal, religious and social uses and these have
increasingly enhanced the demand for this natural product (Elijah et al., 2010). Although, attempts have
been made towards the preservation and shelf-life extension of palm wine
through bottling, use of chemical additives and addition of plant extracts have
greatly affected the organoleptic quality of the product (Obire et al, 2005). Several factors however
have been adduced for this variation and they include the indigenous microbial
flora, the biochemical composition of the two brands of palm sap, the tapping
and post tapping processes.
The palm sap of the palm tree is a rich
medium capable of supporting the growth of several types of microorganisms like
high numbers of aerobic mesophilic bacteria coliforms bacteria, lactic acid
bacteria, acetic acid bacteria and yeasts (Uzogara et al., 1990). Palm wine contains about 10-12% sugar, mainly
sucrose, about 0.3% protein, 10-19 mg/100ml of vitamin C as well as about
160µ/ml of vitamin B12. Saccharomyces
cerevisiae is the dominant yeast specie responsible for the fermentation of
palm wine tapped from Elaeis guineensis
in Ghana and Cameroon, as well as Bandji in Burkina Faso (Ouoba et al, 2012).
1.2 STATEMENT OF THE PROBLEM
Palm wine harbours a large and divergent
group of yeast species which could play important roles beneficial to many
industrial processes involving fermentation. Examples of such processes include
ethanol production, wine and bread making. However, only a very few of these
yeasts are typical fermentative species, such as S. cerevisiae, C.
intermedia or T. delbrueckii, and mild fermentative species mostly H.
uvarum and H. occidentalis (Covadonga et al., 2002). The
quality of these products would greatly depend on the yeast strain (Okunowo et
al., 2005).
1.3 JUSTIFICATION OF THE STUDY
Development of improved starter organisms
for fermentation of palm wine may offer a relatively simple avenue for reducing
post harvest wastage of palm wine in low utilization environment, and in places
where the production of palm wine concentrates is low or non-existent. The
yeast being single cell eukaryotic fungus can be easily modified using various
physical or biological systems (genetics) and the new traits transferred to
their offspring.
1.4
AIM AND OBJECTIVES
The
objectives of this study are to:
1. Extract of Saccharomyces cerevisiae from palm wine.
2. Determine the fermentative ability of the yeast extracted from palm
wine.
3.
Determine the optimum proofing time for the bread produced with the extracted
Saccharomyces cerevisiae.
4. Produce
bread with the extracted Saccharomyces
cerevisia
5. Carry out sensory evaluation of
bread produced with Saccharomyces cerevisiae.
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