ENZYME-INHIBITORS IN TUBER CROPS AND THEIR THERMAL-STABILITY

Tubers of Cassava (Manihot esculenta), yams (Dioscorea esculenta), aro ids (Amorphophallus campanulatus, Colocasia esculenta, Xanthosoma sagi ttifolium) and Coleus (Solenostemon rotundifolius) were screened for i nhibitory activities against amylase, trypsin and chymotrypsin. Coleus tuber possessed the highest anti-amylase activity, whereas Colocasia tuber was the most potent source of anti-tryptic and anti-chymotryptic activity. Xanthosoma tubers exhibited amylase inhibitory activity and Amorphophallus tubers antiprotease activity. Dioscorea esculenta had low levels of amylase and chymotrypsin inhibitors, while Cassava tuber s were totally free of inhibitors. When tubers were processed by press ure cooking, there was significant reduction/complete elimination in i nhibitory activity. Partial retention of inhibition was observed in th e case of amylase inhibitor in Dioscorea, chymotrypsin inhibitor in Co locasia and trypsin inhibitor in Colocasia, Coleus and Amorphophallus. In vitro experiments on heat stability of the different inhibitors re vealed almost similar pattern of inactivation.