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

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

Keywords
Heat–moisture treatment, Canna starch, Plasticizer, Pasting properties

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