Biochemical Changes during Traditional Fermentation of Saudi Sorghum (Sorghum bicolor L.) Cultivars Flour into Khamir (Local Gluten Free Bread).

Effect of traditional fermentation on pH, titratable acidity, proteins, amino acids, and sugars contents of three local sorghum cultivars namely Hamra, Biadah and Shahla used in making khamir local bread were investigated. During 24 fermentations, the pH of fermented dough dropped sharply and this was coincided with increase in total acidity. Fermentation was found to cause no significant change in protein content of the cultivars. Amino acid analysis, revealed slight insignificant improvement in lysine, and leucine content but there was a slight decrease in valine, phenyl alanine and arginine content in fermented dough. Glucose, fructose and maltose content of the three sorghum cultivars increased considerably in the early stages of fermentation, followed by decrease towards the end of fermentation. Low amount of sucrose detected in the three cultivars and it was completely utilized after 8 hrs. of fermentation.

Effects of microwave heat treatment on fungal growth, functional properties, total phenolic content, and antioxidant activity of sorghum (Sorghum bicolor L.) grain.

Sorghum grains were subjected to microwave heating at different power levels 350 and 500 W for application times of 15, 30, and 45 s. The effect of microwave heating on fungal growth, protein content, in vitro digestibility, protein solubility, and functional and antioxidant properties of sorghum grain was investigated. The microwave heating at 350 and 500 W significantly reduced fungal incidence in the grain up to 26.2 and 33.4%. No significant changes were found in the crude protein and digestibility of protein, water holding capacity, and oil holding capacity of sorghum. However, application of microwave energy at 500 W for 30 & 45 s caused a sharp reduction on the protein solubility (8.2-7.6%), foaming capacity (6.47-0.98%), emulsion capacity (0.43-0.32 mL/g) and the emulsion stability (2.2-1.6%) of sorghum grain, respectively. Conversely, a significant increment of grain total phenolic content up to 47.1 and 50.8 mg GAE/g and the antioxidant activity up to 40.9 and 59.1% after microwave heat treatment at 350 and 500 W for 45 s, respectively, was observed. These findings revealed that sorghum grain should be treated with microwave at 350 and 500 W for 45 and 15 s, respectively, in order to maintained and enhanced its functional and nutritional properties. Accordingly, microwave heating, particularly at low power, may be an effective emerging method for improving the physicochemical and nutritional properties of sorghum grain.