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 [α- and β- 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 α-amylase development in ICSV 400. Development of β-amylolytic activity in KSV 8 was however, significantly repressed by Ca²⁺ treatment. Interestingly, β-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.

Key words: Sorghum malt, steep water Ca²⁺ treatment, amylase, CWS-carbohydrate, diastatic power, extract.