Calcium regulation of carbohydrate modification in sorghum

Abstract

Two improved Nigeria sorghum cultivars (KSV 8 and ICSV 400) were used to evaluate the effects of steep water Ca2+ treatment on carbohydrate modification in sorghum. The response of all the carbohydrate mobilization indicators evaluated [- and - amylases, diastatic activity (DP), extract and
cold water soluble carbohydrates (CWS-carbohydrates)], to steep water Ca2+ treatment was highly significantly (p 0.001) cultivar and steep water Ca2+ treatment dependent. In contrast to KSV 8, Ca2+ treatment generally caused significant repression of -amylase development in ICSV 400. Development of -amylolytic activity in KSV 8 was however, significantly repressed by Ca2+ treatment. Interestingly, - amylase activity constituting well over 80% of total diastatic activity was attained in ICSV 400 grains
subjected to 100 ppm Ca2+ treatment. Hot water extract (HWE) showed statistically insignificant (p 0.1) linear variation with Ca2+ treatment. Although Ca2+ treatment significantly (p .001) repressed  CWS carbohydrates in both cultivars, significantly higher CWS-carbohydrates and HWE were released in ICSV 400 for each DP unit than the corresponding DP in KSV 8 malts would permit. Thus, suggesting important roles for factors other than DP, possibly proteolysis, in determining HWE and  CWS carbohydrates. The benefits of reduced kernel growth and malting loss were neutralized by the general repression of carbohydrate modification indices for both cultivars.