Functional Property Of Germinating Sorghum(Sorghum Bicolor L. Moench) And Its Bread Mixed With Wheat Flour

Sorghum(Sorghum bicolor L. Moenc) is one of major crops in the world with many unique characteristics. It has become an important source of energy, protein, minerals, antioxidants, vitamins and gluten free diet for the poor people of Africa and Asia. In Sudan, sorghum is the most important food crop with an annual production of1.4million tons. Improving its available nutrients is vital food quality. Its chemical composition varies greatly with different genotypes and environmental conditions. There is a growing need for improving protein quality and quantity in sorghum grains. Sorghum grains contain relatively low quality proteins and considerable amounts of anti-nutritional factors in comparison with other cereals.Germination is a common practice in sorghum processing industry to enhance the inner hydrolytic enzyme activity and modify its grain structure and components. This process can not only raise the amount of functional components but also improve the protein digestibility and minerals availability by inhibiting anti-nutritional factors. Quality of grain protein quality is usually evaluated based on its amino acids and digestibility.Functional properties of proteins have been defined as those phytochemical properties affecting protein behavior in food as judged by the final product quality. Protein functionality depends on protein size and structure as well as their interactions with other components. They can be modified by various treatments with different functionalities. The functional properties of sorghum proteins can be used to define how flour proteins can be used as supplement or replace more toxic protein sources (e.g. wheat) in food industry.Hence, eliminating anti-nutritional compounds is necessary to improve the nutritional quality of sorghum grain, which will effectively promote commercial utilization of sorghum as human food. In addition, phenolic compounds are generally regarded as desirable components of human food due to their antioxidant activity. There is an increasing demand for natural antioxidants to replace synthetic additives in the food industry as well. This study is the first research to investigate effects of germination on the functional properties of Butanna, a new sorghum cultivar, released by Sudan National Variety Committee in2008. It has high productivity, early maturity and good acceptability in the food market, being suitable for cultivation on sloped drought land. Besides, the experimental results were compared to other two sorghum cultivars. The experiments are designed to.●To investigate physiological and biochemical metabolism of three sorghum cultivars Butanna, Tabat and Wad Ahmed during5days of germination,●To evaluate functional properties and characteristics of proteins in germinating sorghum flour,●To investigated the influence of adding CaC12, PLP and NaCl (to culture solution) on GAD activity and GABA accumulation of germinated sorghum grain,●To measure the contents of anti-nutritional factors, HC1extractability of minerals, total phenolics and, total flavonoids, antioxidant activity and phenolic acid composition of germinating sorghum grains, and●To study the rheological properties of supplementing wheat flour with germinating sorghum on dough and bread quality at different germination times.Experimental results were:(1) Physiological and biochemical metabolism of sorghum grains were compared for three cultivar Wad-Ahmed, Tabat and Butane after5-day germination. The physiological and nutritional characteristics significantly (p<0.05) varied between these cultivars. Root length and respiratory rate increased significantly (p<0.05) during germination. Tabat had the highest germination rate, while Wad-Ahmed had the highest root length and respiratory rate. For all cultivars, a decreasing trend occurred in germination rate, moisture content, crude protein, crude fat and starch content during germination. However, the contents of free amino acids and reducing sugar increased. The highest protein content was in cultivar Butanna, which made it to be selected for our further experiments below. In addition,3-day germination was the most suitable time considering the overall nutritional quality.(2) Butanna grains germinating for three days to investigate protein fractions, protein molecular weight, composition of amino acids, y-aminobutyric acid (GABA) and functional properties.There was an increase in prolamin, glutelin while a decrease in albumin and globulin after3-day germination. Proteins were characterized by sodium dodecylsμlfate- polyacrylamine gel electrophoresis (SDS-PAGE). Under non-reducing conditions as germination was progressing from0to3days, there was visually a decrease in molecular weight. Proteins and their subunits had a wide spectrum of molecular weights, ranging from12kDa to70kDa. Those with a molecular weight between50kDa and70kDa were more abundant in2-and3-day germination than the control and1-day germination. There was an increase in most of essential amino acids except leucine and valine after germination. In addition, the contents of non-essential amino acids, such as proline, glycine and histidine, were largely enhanced during germination. As a result, GABA content increased5folds from1to3-day germination.Germinating sorghum flour had the least gelation concentration of12%compared to16%of the control. Bulk density of the germinating sorghum flours was lower comparison with the control. The flour derived from the germinating grains had higher protein solubility than that in control. The highest solubility occurred at pH10. The highest protease activity was observed at the3rd day in germinating sorghum flour. Germination also increased water and fat absorption capacities of sorghum flour. Its emulsification capacities and stability increased significantly. There was an increase in foaming capacity and a reduction in foam stabilities of all the samples during germination. These results suggested that germinating sorghum grain could be a functional food with rich GABA and health-promoting nutrients.(3) The optimal germination temperature and pH value of culture solution for GABA formation in sorghum grains were studied and selected firstly. The optimal temperature and pH was30℃and6, respectively, for GABA accumulation.Subsequently, the effects of adding NaCl, pyridoxal-5-phosphate (PLP) and CaCl2to culture solution on glutamate decarboxylase (GAD) activity and GABA accumulation of germinating sorghum grains were investigated. To optimize the components in culture medium for GABA accumulation response surface methodology (RSM) were used. Results showed that GAD activity and GABA yield were dependent on the addition of NaCl, PLP and CaCl2into the culture medium. Box-Behnken design indicated that the optimal culture components for GABA accumulation were:NaCl at a concentration of41.07mmol/L, PLP at a concentration of82.63μmol/L and CaCl2at a concentration of0.40mmol/L. Under the optimal conditions, the maximum production of GABA (0.336mg/100g DW) was obtained. Analysis of variance for the regression model suggested that the model can quite exactly predict GABA accumulation in sorghum grains during germination.(4) The changes in tannins, phytic acid, mineral extractability (as an index for mineral bioavaliability), in vitro protein digestibility (IVPD), total phenolics, total flavonoids, antioxidant activity and phenolic acid composition during3-day germination were determined. Changes in the contents of tannin, flavonoids and total phenolics were monitored during the germination. The content of tannin increased by39%after germination for3days. As a result of germination, phytate was significantly(p<0.05) reduced. IVPD was markedly increased, and HC1extractability of both major and trace minerals was improved. The scavenging capacity of sorghum flour against·OH and O2-· tended to increase with germination although no significant difference was observed after1-d germination. Gallic acid,p-Hydroxybenzoic acid, protocatechuic acid and syringic acid present the major phenolic acids in germinating Butanna grains.(5) Germinating sorghum grains were processed into flour and used to substitute wheat flour at different proportions of5%,10%and15%which significantly affected farinograph and extensograph characteristics of the mixed flours. Substitution of wheat flour with germinating sorghum flour decreased the water absorption and dough viscosity. Mixed flour containing5%and10%germinating sorghum flour showed a significant improvement in dough development time, dough stability and softening of dough.Sensory qualities of composite breads were compared using a hedonic scale sensory questionnaire. Results revealed that substitution at5%or10%with germinating sorghum flour gave values as good as the control sample and produced acceptable bread. Germinating sorghum bread was accepted by most consumers, due to a softer and moister crumb and fine malt flavor. The results revealed that germination time for sorghum grain had a significant effect on the sensory profiles of its bread.