Microstructure and physicochemical characteristics of modified taro starch after annealing, autoclaving-cooling and heat moisture treatment

Abstract

This study investigated the effects of annealing, autoclaving-cooling and heat moisture treatment on the microstructure and physicochemical characteristics of taro starch. The taro starch was treated by the annealing process (24 hrs, 50oC), the heat moisture treatment (HMT) (moisture 25%, 3 hrs, 110oC), and the autoclaving (15 mins, 121oC)-cooling (24 hrs, 4oC) with 1 and 2 cycles. The results show that the autoclaving-cooling 2 cycles (AC-2C) changed the microstructure of taro starch into a very compact and dense structure because of formed double helix bound that cannot be hydrolyzed by pancreatic enzymes so it can be converted became resistant starch as the prebiotic source. Pasting properties analysis showed that AC-2C improved shear stress resistance, heat resistance and low retrogradation modified taro starch (MTS). The AC-2C treatment increased water binding capacity (73.84%), solubility (44.58%), and swelling power (16.71%) of MTS. The water-binding capacity had a positive correlation with solubility and swelling power. The AC-2C treatment increased amylose content (27.40%) and decreased reducing sugar level (6.36%) of MTS, so it can encourage the formation of resistant starch to improve the prebiotic properties of taro starch. Modified taro starch AC-2C is the best compared to HMT and annealing based on microstructure and physicochemical characteristics.