ABSTRACT
This study was to determine the microbiological and biochemical changes during fermentation of sorghum bicolor using Saccharomyces cerevisiae. The bacteria species isolated from the fermented sorghum samples, were identified based on their morphological characteristics, pigmentation on media, microscopy, biochemical and sugar fermentation methods while the yeast (Saccharomyces cerevisiae) used for the fermentation of sorghum was isolated using pour plate technique on Sabouraud Dextrose Agar (SDA). This study revealed that mean viable microbial counts varied as the time of fermentation increased. However the viable counts on the fermented sorghum sample were seen to decrease from the fermentation period of 0 hours to fermentation period of 72 hours. The total viable counts on Lactic acid bacteria revealed more counts (6.4x108) at the end of fermentation period (72hours) compared with single cultures. The physical analysis of the fermented sorghum samples in this study also revealed that pH, Temperature and Titratable acid slightly increased by fermentation interval from 0 hour to 72 hours of fermentation respectively. The proximate composition of the fermented sorghum samples revealed that the moisture content, crude fiber, crude protein and crude fat of the samples were high, and This study also revealed Lactobacillus spp as being the most widely distributed and frequently occurring isolates with a high percentage occurrence of 7(42.27%) while Saccharomyces cerevisiae 4(24.26%) was the most widely distributed among fungal species. this could improve the nutritional quality of sorghum. Therefore, the results reported could serve as a starting point to understand the microbiological and biochemical processes in the fermentation of sorghum using Saccharomyces cerevisiae with the aim of improving the efficiency of the process.
TABLE OF CONTENTS
Title
Page i
Certification iii
Dedication iv
Acknowledgement v
Table
of Contents vi
List
of Tables viii
Abstract ix
CHAPTER ONE
1.0 Introduction 1
1.1 Aim and Objectives 3
CHAPTER TWO
2.0 Literature Review 4
2.1 Sorghum 4
2.2 History of
Fermented Foods 4
2.3 Fermentation of Foods 5
2.4 Fermentation
Process 6
2.4.1 Natural
Fermentation 6
2.4.2 Back
Slopping 7
2.4.3 Controlled Fermentation 7
2.5 Alcoholic
Fermentation 7
2.5.1 Traditional
Alcoholic Beverages 8
2.6 Types of
Fermented Cereal Foods 9
2.6.1 Tarhana 9
2.6.2 Togwa 9
2.6.3 Ogi 9
2.6.4 Yosa 10
2.6.5 Balao balao 10
2.6.6
Burukutu 10
2.7 Microorganisms
Involved In Fermentation Process 11
2.1 Lactic Acid Bacteria 12
2.2 Fermentation by Lactic Acid Bacteria Homofermentation
and Heterofermentation 12
2.3 Taxonomical Classification of Lactic Acid
Bacteria 13
2.4 General Position of Specific Lactic Acid
Bacteria 13
2.4.1 Lactobacillus 13
2.4.2 Streptococcus 14
2.4.3 Pediococcus 14
2.5 Occurrence of Lactic Acid Bacteria in
Nature 14
2.6 Saccharomyces
cerevisiae 15
CHAPTER THREE
3.0 Materials and Methods 16
3.1 Sample Collection and Sources of
Commercial Yeast 16
3.2 Isolation of Yeast from Palm Wine 16
3.3 Characterization of Yeast Isolates 16
3.4 Laboratory Preparation of Burukutu
(Fermentation of Sorghum) 16
3.5 Microorganism Used As Starter Culture 17
3.5.1 Preparation and Inoculation 17
3.5.2 Assessment of Fermentation 17
3.6 Biochemical Analysis 17
3.6.1 pH 17
3.6.2 Total Titratable Acidity (TTA) 17
3.6.3 Temperature
17
3.7 Proximate Analysis 18
3.7.1 Mineral Content Determination 18
3.8 Microbiological Analysis 18
CHAPTER FOUR
4.0 Results 19
CHAPTER FIVE
5.0 Discussion and Conclusion
5.1 Discussion 28
5.2 Conclusion 33
LIST OF TABLES
|
S/N
|
TITLE
|
PAGE
NO
|
|
1
|
Mean
Microbial Count of the Fermented
Sorghum Samples
|
22
|
|
2
|
Identification and
characterization of Bacterial Isolates
from Fermented
Sorghum Samples
|
23
|
|
3
|
Cultural Morphology and Microscopic Characteristics
of Fungal Isolates from Fermented
Sorghum Samples
|
24
|
|
4
|
Distribution of Isolates from Fermented Sorghum Samples
|
25
|
|
5
|
Temperature, pH
and Titratable Acid Values of the Samples during Fermentation of Sorghum
Samples
|
26
|
|
6
|
Mineral Composition of Fermented
Sorghum Samples
|
27
|
|
7
|
Proximate Composition of
Fermented Sorghum Samples
|
28
|
CHAPTER ONE
1.0 INTRODUCTION
Fermented
beverages are one of the indispensable components of the dietary culture of
every community in the world. More than any other fermented foodstuffs,
fermented beverages served to enhance social relations between family and group
members as well as among the elite and commoners and to express a relationship
between humans and deities (Dietler, 2006).Sorghum (sorghum bicolor L. moench) is a staple food in most parts of
Africa, where it is the main source of carbohydrates and proteins for millions
of people.
In
Africa, sorghum is used to produce various kinds of traditional beers named sorghum
beer or opaque beers. But depending on geographical location, these beers are
known with different names: Ikakage
in Rwanda (Lyumugabe et al., 2010), pito or burukutu in Nigeria and Ghana
(Achi, 2005) dolo in Burkina faso
(Dickson et al., 2006), amgbain in Cameroon (Lyumugabe et al., 2010), doro or chibuku in Zimbabwe (Chamunorwa et al., 2002) and tchapalo
in Cote d’ivoire (Djè et al., 2008).Fermentation
is widely used traditionally for processing sorghum and fermented products are well
accepted and widely used as complementary foods.
Sorghum (Sorghum bicolor L. Moench) is one of the oldest
known grains (cereals) originating in Africa and India where it is commonly
used in a variety of foods. Sorghum has unique adaptation to Africa’s climate
and it is about the largest cultivated crop in the Northern Guinea Savanna
areas of Nigeria, a tropical region of Africa (Kolawole et al., 2007).
Quantitatively, it is the world’s fifth most important cereal grain after
wheat, maize, rice and barley. Nigeria and the United States are the two
largest producers of sorghum in the world (FAO, 2003). World annual production
is over 60 million tonnes in which Africa produces about 20 million tonnes.
This makes sorghum quantitatively the second most important cereal in Africa
after maize with Nigeria ranking first among Africa sorghum producing countries
and the consumption rate among other cereals all over Nigeria is about 75%
(Taylor, 2004).
Sorghum has achieved the highest growth rate among the food crops
in West Africa and believed to possess the highest capability among available
food crops for attaining technological breakthrough to boost production of food
in any region (Manyong et al., 1996). Production of sorghum is expected
to increase in 2014/15 due to attractive producer prices in the year 2011 and
greater availability of inputs.
Fermentation
of sorghum involves a lot of processes which results in products such as Burukutu or tchapalo. The traditional
process of sorghum fermentation consists of 3 stages:
·
Malting
·
First fermentation
·
Second fermentation
The
processing however involves malting, drying, milling, souring (lactic acid
fermentation), boiling, mashing, alcoholic fermentation and straining (Sawadogo-Lingani
et al., 2007). In which variations
may occur depending on the regional location (Van-der-Aa-Kühle et al., 2001).The malting process
improves the nutritional quality of the product while the fermentation process
improves the safety. The dominance of Saccharomyces
cerevisiae seemed to be a great observation as it plays a major role in the
fermentation process. Due to the central role that sorghum beer plays in
traditional society, it is important that the microbiological and biochemical
changes occurring during the fermentation process be evaluated and noted.
However,
there is a limit to the extent of the study carried out in this context as this
is solely for evaluation of the named changes occurring during fermentation of
sorghum in the presence of yeast (saccharomyces
cerevisiae). This study would be evaluative and comparative as the analysis
would be carried out in 2 phases;
·
The natural fermentation
process
·
The modified process
where the yeast (saccharomyces cerevisiae)
would be added to kick starts the fermentation process.
1.1 AIM AND OBJECTIVES
This
study is aimed at identifying the microbiological and biochemical changes that
occurs during the fermentation of sorghum using saccharomyces cerevisiae, while the specific objectives are;
·
To identify the microbiological
and biochemical changes in the fermentation of sorghum.
·
To evaluate these changes
in relation to when saccharomyces cerevisiae
is added to start up the fermentation process.
·
To evaluate the economic
importance of these changes such as increasing the shelf life of the
fermentation product, increase or decrease in alcohol, microbiological quality
of the product etc.
·
To isolate, enumerate and
identify the dominant microbial species that might have aided the occurrence of
these changes.
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