Effect of fermentation and germination on the in vitro protein digestibility of low and high tannin cultivars of sorghum

Three sorghum cultivars, safra, dabar 1-1 (low in tannin: 0.61 and 0.24%, respectively) and cross 35:18 (high in tannin: 1.10%) obtained from Wad Medani Research Station were used in this study. Safra and cross 35:18 were fermented for 14 h and then the protein was fractionated and the IVPDs of the fractions were determined at 2 h intervals. The IVPD of the protein fractions of the low tannin cultivar increased due to the effect of fermentation and, in the case of the high tannin sorghum cultivar, it increased during the first 6 h of fermentation for the albumin, globulin and prolamin; then it decreased in the remaining period of fermentation. The IVPD of the glutelin fraction increased during the last 6 h of fermentation. Dabar 1-1 and cross 35:18 cultivars were soaked in water for 10 and 20 h and germinated for 72 h. The protein was fractionated every 24 h and the IVPDs of the fractions were determined. For the low tannin cultivar, the IVPDs of the fractions albumin, globulin and glutelin increased, but the IVPD of the prolamin fraction decreased when the grains were soaked for 10 h. When the grains were soaked for 20 h, the IVPD of the fractions albumin, prolamin and glutelin increased, but the IVPD of the globulin fraction decreased. In the case of the high tannin cultivar, the IVPD decreased for all fractions except for the prolamin fraction when the grains were soaked for 10 h.