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INTRODUCTION
The biggest challenge as a result of climate change in Africa and other regions of the world is food insecurity (Brown et al., 2007). Drought will be one of the major impacts of climate change in sub Saharan Africa and alternative cereals like sorghum that are well adapted to harsh climatic conditions will be appropriate in Africa (Hattori et al., 2005). Sorghum is the world’s fifth most important cereal in terms of both production and area planted (FAOSTAT, 2013). The greatest
production of sorghum is concentrated in sub-Saharan Africa (Rooney et al., 2007). Ethiopia is the second largest producer of sorghum (Sorghum bicolor (L.) Moench) in Eastern and Southern Africa after Sudan (FAOSTAT, 2013). In Ethiopia production of sorghum is increasing (CSA, 2011). However, the producers are not benefitted due to limited functionality, utilization, and marketing of sorghum.
LITERATURE REVIEW
This chapter discusses and reviews studies related to the structure and chemistry of sorghum grain with special reference to genetic modification of sorghum starch and proteins, the science and technology of sorghum malting and making sorghum dough-based food products, genetic improvement of sorghum with respect to malting quality and dough–based product quality (with specific reference to fermented flatbreads and biscuits). The genetic improvement of sorghum varieties for food and beverage end-use quality includes both conventional breeding as well as recombinant DNA technology (genetic engineering).
Structure of sorghum grain
The structure and chemistry of the kernel play a crucial role in determining the processing properties and product qualities of a cereal grain. Details of the structure of the sorghum grain have been reviewed by many authors, most notably Serna-Saldivar and Rooney (1995). It should be noted, however, that with respect to the grain morphological characteristics and levels of chemical constituents, notable differences exist even between varieties within cereal grain species. These differences strongly affect the quality of products made from cereal grains (Koehler and Wieser, 2013).
Malting Process
Malting has three physically distinct operations: steeping, germination and drying (Dewar et al., 1997b). These process steps are necessary to ensure the proper occurrence of particular physical and biochemical changes: Steeping – to ensure good absorption of water by the grain (from 12% to at least 40% of moisture); Germination – to maintain embryo growth, enzyme synthesis and limited endosperm breakdown; and Kilning (Drying) – to ensure product stability (Gupta et al., 2010). The well-established barley malting protocols cannot be directly applied to sorghum due to its higher temperature and water requirements during germination (Taylor and Robbins, 1993). Germinating sorghum grains tend to rapidly lose water taken up during steeping. Therefore it is necessary to spray germinating grains at intervals during the germination (Morrall et al., 1986; Dewar et al., 1997a).
DECLARTION
ABSTRACT
DEDICATION
ACKNOWLEDGEMENTS
1 INTRODUCTION
2 LITERATURE REVIEW
2.1 Structure of sorghum grain
2.2 Chemistry of sorghum grain
2.2.1 Starch
2.2.1.1 Waxy sorghum
2.2.2 Proteins
2.2.2.1 Improvement of sorghum protein digestibility
2.2.3 Combining waxy and high protein digestibility traits in sorghum
2.3 Sorghum malting science
2.3.1 Malting Process
2.3.1.1 Steeping
2.3.1.2 Germination
2.3.1.3 Kilning (Drying)
2.3.2 Sorghum malting technologies
2.3.3 Starch hydrolysis during sorghum malting
2.3.4 Proteolysis during sorghum malting
2.4 Research into the effect of starch and protein digestibility on malting quality
2.5 Sorghum dough products
2.5.1 Science of sorghum flatbreads
2.5.2 Research into effect of starch and protein composition on fermented sorghum flatbr quality
2.5.3 Science of sorghum biscuits
2.6 Conclusions
3 HYPOTHESES AND OBJECTIVES
3.1 Hypotheses
3.2 Objectives
4 RESEARCH
4.1 GRAIN CHARACTERISATION OF SORGHUM LINES WITH PRESUMED WAXY (HIGH AMYLOPECTIN) AND HIGH PROTEIN DIGESTIBILITY TRAITS
4.1.1 Abstract
4.1.2 Introduction
4.1.3 Materials and Methods
4.1.3.1 Sorghum samples
4.1.3.2 Sorghum grain endosperm texture
4.1.3.3 Moisture
4.1.3.4 Starch
4.1.3.5 Protein
4.1.3.6 Starch amylopectin
4.1.3.7 In vitro protein digestibility (IVPD)
4.1.3.8 Transmission Electron Microscopy (TEM)
4.1.3.9 Statistical analyses
4.1.4 Results and discussion
4.1.4.1 Grain endosperm texture
4.1.4.2 Protein
4.1.4.3 Starch
4.1.4.4 Waxy (high amylopectin) and high protein digestibility (HD) traits
4.1.5 Conclusions
4.1.6 References
4.2 RELATIONSHIP BETWEEN WAXY (HIGH AMYLOPECTIN) AND HIGH PROTEIN DIGESTIBILITY TRAITS IN SORGHUM AND MALTING QUALITY
4.2.1 Abstract
4.2.2 Introduction
4.2.3 Materials and Methods
4.2.3.1 Sorghum samples
4.2.3.2 Malting
4.2.3.3 Germinative energy
4.2.3.4 Green malt moisture
4.2.3.5 Moisture
4.2.3.6 Starch
4.2.3.7 Protein
4.2.3.8 Transmission Electron Microscopy (TEM)
4.2.3.9 Scanning Electron Microscopy (SEM)
4.2.3.10 Alpha-amylase activity
4.2.3.11 Beta-amylase activity
4.2.3.12 Hot Water Extract (HWE)
4.2.3.13 Free amino nitrogen (FAN)
4.2.3.14 Malting loss
4.2.3.15 Starch and protein losses
4.2.3.16 Statistical analyses
4.2.4 Results and discussion
4.2.4.1 Green malt moisture
4.2.4.2 Malt endosperm modification
4.2.4.3 Protein body degradation
4.2.4.4 Alpha-amylase activity
4.2.4.5 Beta-amylase activity
4.2.4.6 Hot water extract (HWE)
4.2.4.7 Free Amino Nitrogen (FAN)
4.2.5 Conclusions
4.2.6 References
4.3 RELATIONSHIP BETWEEN WAXY (HIGH AMYLOPECTIN) AND HIGH PROTEIN DIGESTIBILITY TRAITS IN SORGHUM DOUGH-BASED (INJERAND BISCUIT) PRODUCT QUALITY
4.3.1 Abstract
4.3.2 Introduction
4.3.3 Materials and Methods
4.3.3.1 Materials
4.3.3.2 Milling
4.3.3.3 Preparation of injera (full-scale method)
4.3.3.4 Preparation of small-scale injera (microwave method)
4.3.3.5 Biscuit making
4.3.3.6 Moisture
4.3.3.7 Starch
4.3.3.8 Protein
4.3.3.9 Crude fat
4.3.3.10 Ash
4.3.3.11 Dietary fibre
4.3.3.12 pH and Titratabile acidity (TA) of the fermenting dough
4.3.3.13 Descriptive sensory analysis
4.3.3.14 Instrumental texture analysis of injera
4.3.3.15 Instrumental texture analysis of biscuit
4.3.3.16 Statistical analyses
4.3.4 Results and discussion
4.3.4.1 Proximate analyses
4.3.4.2 pH and titratable acidity of injera doughs
4.3.4.3 Descriptive sensory analysis of injera
4.3.4.4 Instrumental texture analysis of full-scale injera
4.3.4.5 Instrumental texture analysis of small-scale injera
4.3.4.6 Descriptive sensory analysis of biscuits
4.3.4.7 Instrumental texture analysis of biscuits
4.3.5 Conclusions
4.3.6 References
5 GENERAL DISCUSSION
5.1 Methodological considerations
5.2 Research findings
5.2.1 Relationship between waxy and HD traits in sorghum and malting quality
5.2.2 Relationship between waxy and HD traits in sorghum and dough-based product (inera and biscuit) quality
5.3 Future research and development of waxy sorghums
6 CONCLUSIONS AND RECOMMENDATIONS
7 REFERENCES
8 PUBLICATIONS, PRESENTATIONS AND POSTERS BASED ON THISRESEARCH
