THE USE OF BITTER LEAF (VERNONIA AMYGDALINA) EXTRACT AS A MEANS OF EXTENDING THE SHELF-LIFE OF LOCALLY BREWED SORGHUM BEER


THE USE OF BITTER LEAF (VERNONIA AMYGDALINA) EXTRACT AS A MEANS OF EXTENDING THE SHELF-LIFE OF LOCALLY BREWED SORGHUM BEER

ABSTRACT

Locally brewed beer (sorghum beer) is an indigenous alcohol average. 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 CONTENT

TITLE PAGE……………….……………………………………………………i

CERTIFICATION…………..…………………………………………..………ii

DEDICATION…………….……………………………………………...........iii

ACKNOWLEDGEMENTS…………………………………………………….iv   

ABSTRACT…….………………………………………………………….........v

TABLE OF CONTENTS…………………………………………………........vi

LIST OF TABLES……………………………………………………………xiii

LIST OF FIGURES…………………………………………………………...xiv

CHAPTER ONE

1.0 INTRODUCTION…………………………………………………………. 1

1.1 AIMS AND OBJECTIVES…………………………………………………2

CHAPTER TWO

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…………………………….7

2.2.3 GRAIN COMPOSITION AND NUTRITIVE VALUE…………………………7

2.2.4 CULTIVATION AND USES……………………………………………………9

2.3 MILLET…………………………………………………………………………..10

2.3.1 GENERAL DESCRIPTION OF MILLET……………………………………. 10

2.3.2 BOTANICAL CLASSIFICATION OF MILLET……………………………...11

2.3.3 PEST AND DISEASES OF MILLET………………………………………….11

2.3.4 USES OF MILLET……………………………………………………………..12

2.4 BREWING………………………………………………………………………..13

2.4.1 HISTORY OF BREWING……………………………………………………..13

2.4.2 BREWING PROCESSES………………………………………………………14

2.4.2.1 EUROPEAN BREWING PROCESS………………………………………...14

2.4.2.2 INDIGENOUS AFRICAN BREWING PROCESS………………………….17

2.5 RAW MATERIALS FOR BREWING…………………………………………...18

2.5.1 STARCH SOURCE…………………………………………………………….18

2.5.2 ADJUNCTS…………………………………………………………………….19

2.5.3 WATER………………………………………………………………………...19

2.5.4 HOPS…………………………………………………………………………...20

2.5.4.1 CHARACTERISTICS OF HOPS…………………………………………….21

2.5.4.2 TROPICAL HOP SUBTITUTES FOR BEER BREWING………………….22

2.5.5 YEAST…………………………………………………………………………25

2.5.5.1 BAKER’S YEAST…………………………………………………………...25

2.5.5.2 BREWER’S YEAST…………………………………………………………26

2.6 BIOCHEMISTRY OF BREWING PROCESSES………………………………..26

2.6.1 MALTING AND KILNING……………………………………………………26

2.6.2 MILLING……………………………………………………………………....27

2.6.3 MASHING……………………………………………………………………...27

2.6.4 SOURING………………………………………………………………………29

2.6.5 WORT BOILING………………………………………………………………29

2.6.6 FERMENTATION……………………………………………………………..31

2.6.6.1 ALCOHOL FERMENTATION……………………………………………...35

2.6.6.2 TOP FERMENTATION……………………………………………………..36

2.6.6.3 BOTTOM FERMENTATION……………………………………………….37

2.6.7 PACKAGING…………………………………………………………………37

2.7 SPOILAGE………………………………………………………………………38

2.7.1 MICROORGANISM THAT DETERIORATE BEER………………………...38

2.8 TYPES OF BEER………………………………………………………………...38

2.8.1 EUROPEAN BEERS…………………………………………………………...38

2.8.2 INDIGENOUS AFRICAN BEERS……………………………………………40

2.9 EFFECTS OF ALCOHOL ON MAN……………………………………………45

2.9.1 ALCOHOL AND HEALTH……………………………………………………45

CHAPTER THREE

3.0 MATERIALS AND METHODS………………………………………………...47

3.1 MATERIALS…………………………………………………………………….47

3.1.1 CHEMICALS AND REAGENTS……………………………………………..47

3.1.2 GLASSWARES AND EQUIPMENT…………………………………………48

3.1.3 PREPARATION OF SAMPLES………………………………………………50

3.2 METHODS………………………………………………………………………50

3.2.1 METHOD OF PREPARATION OF SORGHUM BEER……………………..50

3.2.2 ACTIVATION OF YEAST……………………………………………………51

3.2.3 PREPARATION OF BITTERLEAF EXTRACT…………………………….51

3.2.4 PREPARATION OF REAGENT……………………………………………...52

3.2.4.11% PHENOLPHTHALEIN…………………………………………………..52

3.2.4.2 0.1M NaOH SOLUTION…………………………………………………….52

3.3 METHOD OF CHEMICAL ANALYSIS………………………………………..52

3.3.1 TOTAL ACIDITY……………………………………………………………..52

3.3.2 FIXED ACIDITY………………………………………………………………53

3.3.3 VOLATILE ACIDITY…………………………………………………………53

3.3.4 PH DETERMINATION………………………………………………………..53

3.3.5 SPECIFIC GRAVITY………………………………………………………….53

3.3.6 TOTAL DISSOLVED SOLID…………………………………………………54

3.3.7 TOTAL SUSPENDED SOLIDS……………………………………………….54

3.3.8 ETHANOL CONTENT………………………………………………………..55

3.3.9 MICROBIAL COUNT…………………………………………………………55

3.3.9.1 PROCEDURES FOR THE PREPARATION OF MEDIA…………………..55

3.3.9.2 PROCEDURE FOR CULTURING PLATES………………………………..56

3.3.9.3 PROCEDURE FOR IDENTIFICATION OF ORGANISMS………………..57

CHAPTER FOUR

4.0 RESULTS………………………………………………………………………58

4.1 RESULTS FOR TOTAL ACIDITY, FXED ACIDITY, VOLATILE ACIDITY AND PH OF SORGHUM BEER……………………………………….……58

4.2THE GRAPHICAL REPRESENTATION OF TOTAL ACIDITY, FIXED ACIDITY, VOLATILE-ACIDITY AND PH RESULT …………….……….58

4.3 RESULTS FOR ETHANOL CONTENT, SPECIFIC GRAVITY, TDS AND TSS FOR SORGHUM BEER……………..……………………………………….59

4.4 GRAPHICAL REPRESENTATION OF ETHANOL CONTENT, SPECIFIC GRAVITY, TOTAL DISSOLVED SOLIDS (TDS) AND TOTAL SUSPENDED SOLID (TDS) RESULTS ……………………………………60

4.5 AVERAGE MEAN PARAMETERS GENERATED FROM HOPPED AND  UNHOPPED SORGHUM BEER……………………………………………61

4.6 GRAPHICAL REPRESENTATION OF THE AVERAGE PARAMETERS GENERATED FROM SORGHUM BEER WITH AND WITHOUT HOPS………………………………………………………………………….61

4.7 MICROBIAL COUNT FOR BENCH STORED SORGHUM BEER WITH AND WITHOUT HOP……………………………………………………………………62

CHAPTER FIVE

5.0 DISCUSSION……………………………………………………………………64

5.1 CONCLUSION………………………………………………………………….67

5.2 RECOMMENDATION…………………………………………………………68

REFERENCES ……………………………………………………………………..69

APPENDIX A……………………………………………………………………….74

APPENDIX B……………………………………………………………………… ..78

APPENDIX C………………………………………………………………………..79

CHAPTER ONE

1.0   INTRODUCTION

The word beer derives from the Latin word bibere meaning to drink (Okafor, 2007). Beer is the world’s oldest and most widely consumed alcoholic beverage and the third most popular drink overall after water and tea. Grossman (1995) defined beer as a general name given to beverages resulting from the germination of a malt or cereal grain. The process of brewing beer is called brewing. It is produced by the brewing and fermentation of starches mainly derived from cereal grains most commonly malted barley, although wheat, maize (corn), and rice are widely used (Gutcho, 1976). In Nigeria today, barley has been replaced by some locally grown cereals such as sorghum or guinea corn, millet and maize as the principal raw materials. The tropical beers (African local beers) are known by different names in different part of the world; burukutu, otika and pito in Nigeria, maujek among the Nandi’s in Kenya, mowa in Malawi, kaffir beer in South Africa, merisa in Sudan, bouza in Ethiopia and pombe in some parts of East Africa (Okafor, 2007).

Burukutu is an indigenous alcoholic beverage. Burukutu, a popular alcoholic drink among indigenes of the middle belt region of Nigeria, is a local brew made from fermented sorghum and other protein enriched grains (Ekundayo, 1969). The age long drink, also known as BKT, serves as a source of alcohol for those who lack the financial means to patronize refined brew like beer and other foreign or imported drinks it is produced mainly from the grains of guinea corn (Sorghum vulgare and 

Sorghum bicolor). The process of production of burukutu involves malting, mashing, fermentation and maturation as described by Ekundayo (1969).The production process of these indigineous drinks involves fermentation at its initial production stage and comes out as an alcoholic drink. The microorganisms associated with fermentation include Saccharomyces cerevisiae, Saccharomyces chavelieria and Leuconostocmesteroides (Faparusi et al., 1973).

 Sorghum is a large variable genus with many cultivars (Ettasoe, 1972). The method employed in brewing sorghum beer here involves, malting, mashing, wort boiling with hops, fermentation, (using brewer’s yeast and bakers yeast) and packaging. The tropical sourced hop extracts used here is Vernonia amygdalina (Bitter leaf) which have been found to contain an anti bactericidal agent which is capable of extending the useful life of these indigenous beers (Okoh et al., 1999).

Chemical analysis on the prepared sorghum beer such as; ethanol content, PH value, specific gravity, fixed acidity, total acidity, total dissolved solids (TDS), total suspended solids(TSS) were analysed quantitatively, using different methods.

1.1 AIMS AND OBJECTIVES

The aim of the project is itemized into the following objectives;

1.  To determine the shelf-life of locally brewed sorghum beer.

2.  To check the effect of bitterleaf  (Vernonia amygdalina) extract  on the locally brewed sorghum beer.

3. To compare the results from the chemical analyses of locally brewed sorghum beer with bitterleaf extract and sorghum beer brewed without bitterleaf.

.

THE USE OF BITTER LEAF (VERNONIA AMYGDALINA) EXTRACT AS A MEANS OF EXTENDING THE SHELF-LIFE OF LOCALLY BREWED SORGHUM BEER



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