Changes in tannin and cyanide contents and diastic activity during germination and the effect of traditional processing on cyanide content of sorghum cultivars

Abstract

Investigation of three sorghum cultivars showed that tannin content of ungerminated seeds were 220, 410 and 400 mg/100 g for Waznashra, Feterita and Gadamelhamam cultivars, respectively. For all cultivars, ungerminated seeds were found to contain no free or total cyanide. Their diastatic activities (the combined α- and β-amylase activities) were found to be zero. For all cultivars, tannin content was slightly increased when seeds were germinated for different periods. Both free and total cyanide were significantly increased with the length time of germination for all cultivars. Fermentation and heat treatment of germinated seeds significantly reduced cyanide content and only traces were detected in the final product (Hulu-murr and Merissa). Fermentation alone was found to reduce cyanide content, although not as much as when it was accompanied by heat treatment. Diastatic activity markedly increased with time of germination for Feterita and Gadamelhamam cultivars while for Waznashra it increased markedly up to day 3 after which it started to decline rapidly. Results indicated that germination of sorghum seeds for different periods increased tannin and cyanide contents, while changes in diastatic activity depend on type of cultivar. Traditional processing was found to reduce cyanide contents of germinated seeds.