Caracterização da dupla modificação física em propriedades termoanalíticas, físico-químicas, estruturais e de pasta da fração amilácea de taro (colocasia esculenta l. schott) orgânico

Abstract

Taro (Colocasia esculenta L. Schott) is a tuber that possesses up to 80% of starchy material in its composition (dry basis) and the size of its granules ranges from 1 μm to 6 μm, while other fonts may have granules up to 100 μm. Native starches can present technological processing limitations, and thus, physical, chemical and biological modifications are performed to improve its application range. In this study, organic taro starch was modified by heat-moisture treatment (HMT), with different moisture levels (13, 19 and 25%) and different time intervals (45, 60 and 75 min). All treatments were performed at 120 °C followed by ultrasound (US) for dual modification. The US was applied for 30 min and 60% of amplitude, at a fixed frequency of 20 kHz, for all samples. The morphology of the native and modified samples where evaluated by scanning electron microscopy (SEM), the pasting properties by viscoamilography (RVA), the gelatinization event by differential scanning calorimeter (DSC) and cristallinity pattern by X-ray difratometry. The major differences where in the relative crystallinity that increased from 26.9% to 32.7%. Additionally, the pasting profile showed a decrease in all parameters. The gelatinization showed an enthalpy increase for all HMT-modified samples, up to 14.88 J/g (native sample: 9.45 J/g). Moreover, a peak broadening was observed, suggesting higher heating stability. Due to this, previous studies suggest that HMT starch can be used in canned and frozen food. The dual modified samples resulted in gelatinization shortening and had a decrease in enthalpy, reaching 4.1 J/g at the minimum. This is due to the higher hydration and lower swelling power of the granule, which indicates a good dispersibility. This gives the taro potential to be used in biodegradable films. Keywords: modified starch, ultrasound, heat-moisture treatment, non-convetional starch.