EFFECTS OF AIR REST PERIOD ON THE MOBILISATION OF SORGHUM RESERVE PROTEINS

Abstract

The influence of air rest treatment period on the mobilisation of storage proteins of two improved Nigerian sorghum cultivars ICSV 400 and KSV 8 was evaluated. Grains were steeped in distilled water for a total period of 48 h at 30°C with a 6 h final warm steep at 40°C under four different cycles incorporating 1, 2, 3 or 4 h air rest period respectively. Cold water soluble protein, cold water soluble protein modification index, total cold water solubles, total free alpha amino acid nitrogen, carboxy-peptidase and proteinase activities were determined after 6 days malting. All these protein modification indices were highly significantly affected by length of air rest and cultivar, plus their pair-wise interactions. The levels of all these variables were also higher in sorghum cultivar ICSV 400 compared to KSV 8 except for proteinase activity. Significant differences in grain storage protein complexity and structure coupled with probable differences in key proteinase iso-forms are advanced as possible explanation for the higher proteinase activity recorded in KSV 8 malts.