Effects of dual modification on thermal, structural and pasting properties of taro (Colocasia esculenta L.) starch

Abstract

In this study, organic taro starch was submitted to dual modification: the first modification was by heat-moisture treatment (HMT), which totalled nine treatments, combining three moisture levels (13, 19 and 25%), three time intervals (45, 60 and 75 min) and a temperature of 120 °C, and the second modification was by ultrasound (US), which was applied for 30 min at 60% amplitude (frequency of 20 kHz) for all the samples. The morphology of the granules did not show major changes; the relative crystallinity decreased after HMT and increased after the second treatment by US, varying between 26.9 and 32.7%. The Rapid Visco Analyser (RVA) profile showed a decrease in all parameters, except for the pasting temperature. The gelatinisation showed an increase in enthalpy change for all the HMT-modified samples, up to 14.8 J g−1. Moreover, an extension of the gelatinisation range also occurred, suggesting a higher stability in relation to heating; the values ranged from 9.3 (native sample) to 16.7 J g−1 for the HMT-modified sample. The dual-modified samples resulted in a lower gelatinisation temperature range and a decrease in enthalpy change; 4.1 J g−1 was the lowest value. The chemometric approach resulted in a better understanding of the behaviour of the samples modified by dual modification.