The effect of various cations, anions, acids and oxidising agents on the gelatinisation properties of cassava starch was studied and wide variation was observed in the pasting and swelling properties. Sodium chloride and sodium thiosulphate slightly lowered the peak viscosity of cassava starch with increase in concentration, whereas with sodium sulphite, calcium chloride and sodium hypochlorite, a more significant decrease in the viscosity and breakdown was observed. Ferrous sulphate, alum, aluminium chloride and acids enhanced the peak viscosity at lower concentrations followed by a decrease at 1% and above. Sodium metabisulphite elevated the viscosity at 0.05 and 0.1%, while sodium hypochlorite lowered the viscosity and breakdown. DSC studies showed that aluminium chloride, sodium sulphite, and sodium thiosulphate brought about an increase in T onset , T end and DH values at higher concentrations. A decrease in swelling volume was observed from 0.05 to 1% concentration of sodium chloride and above that there was a gradual increase. With sodium sulphite, a significant increase in swelling volume was observed at 2.5 and 5% levels. With 0.05 and 0.1% aluminium chloride and sodium metabisulphite an increase in swelling volume was noticed, but at higher concentrations there was a drastic fall. Sodium chloride, sodium sulphite, sodium thiosulphate and calcium chloride brought about decrease in starch paste clarity with increase in salt concentration, whereas ferrous sulphate, aluminium chloride, sodium hypochlorite, hydrochloric acid and acetic acid improved the starch paste clarity.

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The proteinase and -amylase isoinhibitors of lesser yam were isolated through TCA precipitation and DEAE cellulose chromatography. The major peak with proteinase inhibitor activity obtained by DEAE-cellulose chromatography was further fractionated to five isoinhibitor fractions with molecular weights 67, 50, 27, 15, and 12 kDa respectively in GPC and PAGE. On the contrary, the major peak with -amylase inhibitor activity segregated into four isoinhibitors with molecular weights 63, 31, 24, and 16 kDa. Unlike most trypsin inhibitors the lesser yam proteinase inhibitors (LYTI) exhibited proportionate decrease in trypsin inhibition with increase in inhibitor concentration. The inhibitor potential of lesser yam -amylase inhibitor (LYAI) however, increased with increase in inhibitor concentration. The LYTI was fairly thermostable, retaining 50% activity even after heating for 4 h at 90 C, while the LYAI was much less stable at this temperature. Out of the five fractions of LYTI, isoinhibitors II and IV possessed anti-chymotryptic activity, while isoinhibitors I and V exerted 16 and 25% inhibition of -amylase respectively. The study showed the existence of bi-functional trypsin/amylase and trypsin/chymotrypsin inhibitors, which also ORDER REPRINTS exhibited glycoprotein nature. Although red flour beetle proteases and -amylases were not inhibited by the LYTI and LYAI, mild inhibition was observed against the respective enzymes of coffee bean weevil, rice weevil, and sweet potato weevil.

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