Pasting properties of heat-moisture treated canna starches using different plasticizers during treatment

Different plasticizers (propanol, propylene glycol, glycerol, erythritol, xylitol and sorbitol) were used for plasticizing canna starch during heat-moisture treatment (HMT). Pasting properties of the modified starches were determined and compared with those of native starch and of HMT starch using water as a plasticizer. Canna starch was soaked in 5% (w/w) plasticizer solutions and adjusted to 25% moisture content before heating at 100 °C for 1 h. The least change in paste viscosity was found when water was used as a plasticizer. Viscosity of the modified starches decreased as the molecular weight of plasticizers decreased. Plasticizer content in starch granules increased with decreasing molecular weight of the plasticizer, as well as with increased soaking time (from 10 min to 4 and 24 h). However, pasting profiles of HMT starches prepared by soaking for 4 h were comparable to those soaked for 24 h, indicating that there was an effective limit of plasticizers. The plasticizer content in starch granules played a greater role in HMT than the number of hydroxyl groups.