Physicochemical properties, resistant starch content and enzymatic digestibility of unripe banana, edible canna, taro flours and their rice noodle products

Unripe banana, edible canna and taro flours, which have been reported to contain significant amounts of fibre, were investigated for their physicochemical properties, resistant starch (RS) content and in vitro starch digestibility, and compared with commercial high-fibre-modified starches from corn and tapioca. Differential scanning calorimetry showed a single endothermic peak located around 70-83 degrees C for the samples except the modified starches, which exhibited no transition enthalpy. The samples showed different pasting behaviours in the Rapid Visco-Analyser (RVA) ranging from full to restricted swelling. The RS content varied from 1-26 g per 100 g dry sample, and the estimated glycaemic indices (GIs) of the samples were from 67% to 99%. Generally, samples with high RS were low in GI values. The starches produced acceptable rice noodles but with reduced rate of starch digestion and GI. The effects of the unripe banana, edible canna and taro flours on starch digestibility were either comparable or better than the commercial modified starches. These flours can substitute commercial modified starches to lower GIs of noodles and identical foods.