Concentration of plasticizers applied during heat-moisture treatment affects properties of the modified canna starch

Effects of the concentration of plasticizers applied during heat-moisture treatment (HMT) on the properties of canna starch were investigated. The modified starches were prepared by soaking starch in 0 (water), 1, 3, 5, 10, 20 and 30% w/w glycerol or sorbitol solution for 24h and adjusting the moisture content to 25% before HMT (100°C, 1h). Changes in the pasting profiles of heat-moisture treated starches were more obvious when glycerol solutions were used instead of water. An increase in the concentration of glycerol solution from 1% to 5% resulted in a progressive decrease in paste viscosity; paste viscosity then increased as the glycerol concentration rose from 10 to 30%. A similar trend was observed when sorbitol was used as a plasticizer, but with a lesser effect. A scheme for arrangements of the molecular structure of starch during the process of HMT was suggested.