MICROWAVE POPPING CHARACTERISTICS, CHEMICAL COMPOSITION AND MICROSTRUCTURE OF SORGHUM GRAIN

The chemical composition, physical properties (moisture, crude protein, crude fiber, ash content, thousand grain weight, bulk density) and grain microstructure were evaluated for different varieties of sorghum grain cultivated in Ukraine. Sorghum varieties (Dniprovsky, Kafrske, and Fulgus) were subjected to different preconditioning and process parameters of microwave heating to determine the popping characteristics of the grain. Each of the three sorghum varieties was pretreated by moisture conditioning up to 13, 15, and 17%, and popped in a microwave oven set at 450, 600 and 700 W for 150 s. Popping yield was insufficient for all sorghum varieties at microwave power 450 W and grain moisture content of 13 and 17%. Popping characteristics (popping yield, popping start, specific weight of popped grain and volume expansion ratio) and organoleptic properties were measured. Thousand grain weight, bulk density, protein, ash, crude fiber content, pericarp, aleurone, and translucent endosperm thickness were found to be significantly different among the three sorghum varieties. Varietal characteristics of sorghum grain had a strong impact on volume expansion ratio, which was negatively correlated with the size of the grain. The Fulgus grain variety showing the highest popping characteristics was found to have higher thousand grain yield (31.9 g), higher bulk density (869.8 g/dm(3)), lower protein (8.03%), ash (1.35%) and crude fiber (2.01%) content, thinner but well-packed pericarp (31 mu m), thinner aleurone (9 mu m) and thicker translucent endosperm (1.1 mm) than other varieties.