β-GLUCAN AND β-GLUCANASE LEVELS IN IMPROVED SORGHUM VARIETIES DURING MALTING AND THEIR EFFECTS IN BREWING

ABSTRACT

Levels
of β-glucan components (TBG: total β-glucan, WIBG: water insoluble β-glucan and
WSBG: water soluble β-glucan) and β-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 β-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 β-(1→3:1→4)-glucanase
levels were significant (P ˂ 0.05).
However, their effects on the WSBG levels of malt varieties were not
significant. β-Glucan and β-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.

TABLE
OF CONTENTS

CHAPTER                                          TITLE                                                          PAGE

         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 

1.1       Background of Study…       
…       …        …        …        …        …             1

1.2       Statement of Research Problem          …        …        …        …        …             1

1.3       Objectives of the Study          …        …        …        …        …        …            
2

1.4       Research Hypotheses              …        …        …        …        …        …             3

1.5       Justification of the Study       …        …        …        …        …        …            
3

1.6       Scope and Limitations of the Study               …        …        …        …           
5

         

        CHAPTER
TWO:        REVIEW OF RELATED LITERATURE

2.1       The Sorghum Grain     …        …        …        …        …        …        …             7