Effect of fermentation on protein fractions and tannin content of low- and high-tannin cultivars of sorghum

Abstract

Two sorghum cultivars-safra (low in tannin, 0.612%) and cross 35 : 18 (high in tannin, 1.104%)-obtained from Wad Medani Research Station were used in this study. The percentage of the protein fractions albumin, globulin, prolamin, glutelin and insoluble fraction for the safra cultivar were 11.5%, 8.2%, 60.2%, 10.2% and 10.1%, respectively, and for the cross 35 : 18 cultivar 10.0%, 4.7%, 67.9%, 9.4% and 8.1%, respectively. The tannin contents of fractions for the safra cultivar were 0.228%, 0.052%, 0.028% and 0.304% for the first four fractions, respectively, and for the cross 35 : 18 cultivar 0.376%, 0.056%, 0.136%, 0.536%, respectively, for the first four fractions. The two varieties were fermented for 14 h and the protein fractions and the tannin content of the fractions were determined at 2-h intervals. Results indicated that there was a decrease in the prolamin fraction, an increase in the glutelin and a slight increase in the albumin and globulin fractions for the safra cultivar. In the second cultivar, the prolamin content fluctuated during fermentation while the glutelin fraction increased towards the end of fermentation and the albumin fraction increased at the beginning of fermentation but decreased at the end. Most of the tannin was associated with the glutelin and albumin fractions. Fermentation decreased the tannin content for both cultivars, and the decrease of tannin reached 92% in the high-tannin variety. The tannin content of the protein fractions decreased during fermentation, especially in the albumin and glutelin fractions. © 1994.