Influence of Gamma Radiation and Processing on Anti-nutritional Factors and Nutritive value of grains of Three Sorghum {Sorghum bicolor (L.)Moench} cultivars

Abstract

Influence of Gamma Radiation and Processing on Anti-nutritional Factors and Nutritive Value of the Grains of Three Sorghum {Sorghum bicolor (L). Moench} Cultivars By Ismat Gorashi Abd Allah Mohammed Abstract: The aim of this work was to investigate the effect of Gamma radiation and different processing on the anti-nutritional factors and nutritive value of the grains of three sorghum (Sorghum bicolor L. Moench) cultivars; namely, Dabar, Wad Ahmed and Karamaka sorghum grains were they are different tannin –containing cultivars. Irradiation was conducted using three doses of 5, 10 and 15KGy. The treatments were irradiation, fermentation, cooking and fermentation followed by cooking. Tannins and phytate were the target anti-nutritional factors. The parameters analysed were in vitro protein digestibility, minerals, amino acids, tannin and phytate. Preliminary analysis showed that Karamaka had the highest tannin content (2.9% as catechin equivalent), while Dabar had the lowest (0.1% as catechin equivalent). The grains of the three cultivars had almost similar phytate content a range of 266 - 272 mg/100 g. Karamaka had the lowest in vitro protein digestibility (35.2%) which could be due to the high tannin content. The availability of major and trace elements was relatively low which could be attributed to the grain phytate content. The grains of the three sorghum cultivars were relatively rich in some of the essential amino acids such as isoleucine, leucine, phenylalanine, tyrosine and valine, and poor in lysine, methionine, cysteine and threonine relative to FAO/WHO/UNU reference values. Irradiation and /or processing significantly (PX04;0.05) reduced tannins and phytate contents in the three cultivars. The highest reduction in tannin content (84.7%) in Karamaka due to the irradiation followed by cooking of fermented dough. The highest phytate reduction (65.21%) was in Dabar by irradiation followed by fermentation. Tannins and phytate contents significantly (PX04;0.05) decreased with increasing irradiation dose, while in vitro protein digestibility increased. Fermentation of sorghum grains significantly (PX04;0.05) improved its in vitro protein digestibility, and the highest increase (81.11%) was in Dabar obtained by irradiation followed by fermentation. Major and trace elements availability was significantly (PX04;0.05) improved by fermentation and irradiation doses of 10 and 15KGy although the best results were obtained by irradiation followed by fermentation. Cooking reduced the availability of all minerals in sorghum grains. Irradiation and cooking treatments drastically affected amino acid levels, yet fermentation has improved most of the amino acid levels specially Lysine which is considered a limiting amino acid in sorghum proteins