The Effect Of Bitter Leaf (Vernonia Amygdalina) Extract On The Microbial Load And Shelf- Life Of Locally Brewed Sorghum Beer (Burukutu)

ABSTRACT

Locally brewed beer (sorghum beer) is an indigenous alcoholic beverage. It is produced mainly from sorghum grain (Sorghum vulgare) and the process of brewing involves malting, mashing, souring, fermentation and packaging. Locally brewed beer without hops has a short shelf-life. The aqueous extract of a tropical plant, bitter-leaf was used as the hop .Two type of drink were produced, one with hops and another without hops. Chemical analyses were carried out on both drinks, which gave a significant (p≤0.05) difference. Sorghum beer with hops has a total acidity of 0.562±0.03, fixed acidity of 0.203±0.001, Volatile acidity 0.360±0.02, PH 3.93, specific gravity 1.042±0.003, total dissolved solids 1.12×105ppm, total suspended solids 1.65×105ppm, ethanol content of 3.43±0.03 respectively. While sorghum beer without hops has a total acidity of 0.652 ±0.002, fixed acidity of  0.176±0.002, volatile acidity of 0.476±0.03, PH of 3.50 specific gravity of 1.021±0.003,  total dissolved solid of 1.15×105ppm, total suspended solids of 1.5×105ppm and an ethanol content  of 3.65±0.02. The microbial count for sorghum beer with hop had no growth of E.coli, streptococcus and staphylococcus but aspergillus was present from the 4th day and heaviest on the 8th day. While the drink without hop had growth of staphylococcus and aspergillus which was seen from the 2nd day and heaviest on the 4th day but E.coli and streptococcus was absent. From the results, the drink with hops could keep for a longer period of time than the other drink without hops. Thus, the aqueous extract of Vernonia amygdalina could extend the shelf-life of locally brewed sorghum beer.

TABLE OF CONTENTS ﾿ PAGE

Title Page ﾿ i

Certification ﾿ ii

Dedication ﾿ iii

Acknowledgement ﾿ iv

Table of Contents ﾿ v

List of Table ﾿ ix

List of Figures ﾿ x

Abstract ﾿ xi

CHAPTER 1

1.0 ﾿ Introduction ﾿ 1

1.1 ﾿ Aims and Objectives ﾿ 2 ﾿

CHAPTER 2

2.0 ﾿ Literature Review ﾿ 4

2.1 ﾿ General Description Of Cereals ﾿ 4

2.1.1 ﾿ General Characteristics Of Cereals ﾿ 4

2.2 ﾿ Sorghum ﾿ 5

2.2.1 ﾿ General Description Of Sorghum ﾿ 6

2.2.2 ﾿ Scientific Classification Of Sorghum ﾿ 6

2.3 ﾿ Some Examples Of Indigenous Beers ﾿ 7

2.3.1 ﾿ Pito ﾿ 7

2.3.2 ﾿ Kunu ﾿ 7

2.3.3 ﾿ Burukutu ﾿ 8

2.4 ﾿ Physicochemical And Microbiological ﾿ 9 

2.4.1 ﾿ Nutritive Value Of Burukutu ﾿ 10

2.4.2 ﾿ Economic Value Of Burukutu ﾿ 10

2.5 ﾿ Brewing ﾿ 11

2.5.1 ﾿ History Of Brewing ﾿ 11

2.5.2 ﾿ Indigenous African Brewing Process ﾿ 12

2.6 ﾿ Raw Materials For Brewing ﾿ 12

2.6.1 ﾿ Starch Source ﾿ 13

2.6.2 ﾿ Adjuncts ﾿ 13

2.6.3 ﾿ ﾿ Water ﾿ 14

2.6.4 ﾿ Hops ﾿ 14

2.7 ﾿ Bitter Leaf (Tropical Hop substitute for Beer Brewing) ﾿ 17

2.7.1 ﾿ Botany ﾿ 19

2.7.2 ﾿ Major Uses And Functions ﾿ 19

2.8 ﾿ Yeast ﾿ 19

2.8.1 ﾿ Baker’s Yeast ﾿ 20

CHAPTER 3

3.0 ﾿ Materials And Methods ﾿ 21

3.1 ﾿ Materials ﾿ 21

3.2 ﾿ Methods ﾿ 21

3.2.1 ﾿ Collection Of Samples ﾿ 21

3.2.2 ﾿ Preparation Of Burukutu ﾿ 21

3.2.3 ﾿ Preparation Of Yeast For Inoculation ﾿ 23

3.2.4 ﾿ Fermentation Of Sorghum Wort ﾿ 23

3.3 ﾿ Physiochemical Analysis ﾿ 25

3.3.1    ﾿ Total Acidity ﾿ 25

3.3.2      ﾿ Fixed Acidity ﾿ 25

3.3.3 ﾿ Volatile Acidity ﾿ 25

3.3.4 ﾿ Total Suspended Solid (TSS) ﾿ 26

3.3.5      ﾿ Ethanol Content ﾿ 26

3.3.6 ﾿   ﾿ Measurement of Ph ﾿ 27

3.4          ﾿ Determination Specific Gravity ﾿ 27

3.4.1      ﾿ Total Dissolve Solid ﾿ 27

3.5 ﾿ Microbiological Analysis of Burukutu ﾿ 28

3.5.1 ﾿ Sterilization of Materials ﾿ 28

3.5.2 ﾿ Media preparation ﾿ 28

3.5.3 ﾿ Isolation of Identification of Bacteria in Treated and Untreated  Burukutu Sample

3.6 ﾿ Microbiological Examination Of Isolates ﾿ 30

3.6.1  ﾿ Gram Staining ﾿ 30

3.6.2 ﾿       ﾿ Spore Staining ﾿ 31

3.6.3      ﾿ Motility Test ﾿ 31

3.7    ﾿     ﾿ Biochemical Test ﾿ 32

3.7.1      ﾿ Catalase Test ﾿ 32

3.7.2      ﾿ Coagulase Test ﾿ 32

3.7.3      ﾿ Oxidation Test ﾿ 32

3.7.4      ﾿ Sugar Fermentation Test ﾿ 33

3.8        ﾿ Fungal Isolation and Identification ﾿ 33

3.8.1 ﾿ Preparation of Bitter leaf Extract ﾿ 33

3.8.2  ﾿ Statistical Analysis Method ﾿ 34

CHAPTER 4

4.0 ﾿ Results ﾿ 35

CHAPTER FIVE

Discussion, Conclusion And Recommendation

5.0 ﾿ Discussion ﾿ 40

5.1 ﾿ Conclusion ﾿ 43

5.2 ﾿ Recommendation ﾿ 44

REFERENCES ﾿ 45

APPENDIX