ABSTRACT
Levels of glucan components (TBG: total glucan, WIBG: water insoluble glucan and WSBG: water soluble glucan) and glucanase in three improved sorghum varieties (SK5912, KSV8 and ICSV400) during malting and their effects in brewing were investigated using standard methods. Variety ICSV400 had the lowest TBG, WIBG and WSBG levels of 0.298 ± 0.054%, 0.196 ± 0.021% and 0.102 ± 0.015% in its raw samples and 0.187 ± 0.007%, 0.144 ± 0.004% and 0.043 ± 0.006% in malt samples, respectively. Variety SK5912 had the highest TBG, WIBG and WSBG levels of 0.376 ± 0.037%, 0.246 ± 0.03 and 0.130 ± 0.015% in its raw samples and the highest total mean WIBG of 0.167 ± 0.020% in its malt samples, respectively.
Similarly, variety KSV8 had TBG and WIBG levels of 0.362 ± 0.035% and 0.233 ± 0.023% in its raw samples and the highest TBG and WSBG levels of 0.236 ± 0.030% and 0.076 ± 0.008% in its malt samples. The trend indicated that levels of glucan components in the sorghum varieties depended on their original levels in the raw grains and not on enzymic degradation during malting. However, more WSBG components (~30 – 65%) were degraded than its WIBG counterparts (~20 – 43%) across the sorghum varieties. Endo-β-(1→3:1→4)-glucanase levels in all the sorghum malt varieties consistently increased during the malting period. ICSV400 malts developed the highest total mean enzyme level of 13.122%, SK5912 had 11.207% level while KSV8 malts developed the least level of 8.568%.
The effects of variety, germination time and variety plus germination time interaction on the TBG, WIBG and (1→3:1→4)- glucanase levels were significant (P ˂ 0.05). However, their effects on the WSBG levels of malt varieties were not significant. Glucan and glucanase levels in the sorghum grain and malt varieties significantly (P ˂ 0.05 and P ˂ 0.01) correlated with other malt quality parameters. On the basis of the results, variety ICSV400 is preferred as malting and brewing raw material to SK5912 and KSV8 varieties.
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Cover Sheet
Title Page…………i
Declaration…………ii
Certification…………iii
Dedication… … … …iv
Acknowledgements………v
Abstract…………vi
Table of Contents………vii
List of Tables …………xii
List of Figures…….…xiii
List of Appendices………xiv
List of Abbreviations and Symbols…xv
CHAPTER ONE:INTRODUCTION
1.1Background of Study …………………1
1.2Statement of Research Problem……………1
1.3Objectives of the Study………………2
1.4Research Hypotheses………………3
1.5Justification of the Study………………3
1.6Scope and Limitations of the Study…………5
CHAPTER TWO:
REVIEW OF RELATED LITERATURE
2.1The Sorghum Grain… … … … ………7
2.2Morphology, Anatomy and Chemical Composition ………8
2.3Sorghum Malting… … … … ………14
2.4Maltable Cereals…………………16
2.5Economic Importance ………… ...……18
2.6Nutritional Value…………………18
2.7Uses of Sorghum…………………24
2.8Cereal Glucan and their Degradation during Malting and Brewing …………………26
2.9Comparative Biochemical and Physiological C hanges in
Sorghum and Barley during Germination…………29
CHAPTER THREE:
MATERIALS AND METHODS
3.1Source of Materials…………………33
3.2Analytical Methods…………………36
3.2.1Analyses of Grain Samples…….…………36
3.2.2Moisture Content…………….……36
3.2.3Germination Energy………….….……37
3.2.4Germination Index…………….……37
3.2.5Total Nitrogen ……………………37
3.2.6Crude Protein ……………………39
3.2.7Total Glucan…………………39
3.2.8Theory and Principle of Assay Procedure…………40
3.2.9Assay Procedure for Grain Glucan Determination ………40
3.2.10Reagent Blanks…………………43
3.2.11Glucose Standards…………………43
3.2.12Glucose Oxidase/peroxidase Reagent ……………43
3.2.13Water- insoluble Glucan………………44
3.2.14Water-soluble Glucan………………44
3.3Malting Procedure… ...……………44
3.3.1Steeping……………………44
3.3.2Germination……………….……46
3.3.3Kilning……………………46
3.4Analyses of Malt Samples………………48
3.4.1Moisture Content………….….……48
3.4.2Malting Loss ……………………48
3.4.3Total Nitrogen …………….….……48
3.4.4Total Glucan……….…………49
3.4.5Theory and Principle of Assay Procedure…………49
3.4.6Assay Procedure for Malt Glucan ……………49
3.4.7Water- insoluble Glucan………………50
3.4.8Water-soluble Glucan………………50
3.4.9Malt Endo-Glucanase Activity……………50
3.4.10Theory and Principle of Assay Procedure…………50
3.4.11Extraction of Crude Malt Glucanase…………51
3.4.12Assay Procedure for Malt Endo-Glucanase………51
3.4.13Reaction Blank…………………53
3.4.14Precipitant Solution…………………54
3.4.15Extraction Buffer…………………54
3.5Mashing and Wort Production……………54
3.6Analyses of Wort Samples………………56
3.6.1Filtration Rate ……………………56
3.6.2Specific Viscosity…………………56
3.6.3Reducing Sugar…………………57
3.6.4Reagent Solutions…………………57
3.6.5Theory and Principle of Assay Procedure…………58
3.6.6Assay Procedure…………………58
3.6.7Specific Gravity…………………59
3.6.8Original Extract…………………59
3.7Experimental Design …………………60
3.8Statistical Analyses