Combination of organic acid and heat–moisture treatment: impact on the thermal, structural, pasting properties and digestibility of maize starch

Maize is the most important source of starch used for industrial applications. Its starch properties can be improved by either single or double modification. Heat–moisture treatment (HMT) and acid modification are known to promote an increase in the levels of slowly digestible starch and resistant starch (RS). In this study, maize starch was treated by conventional HMT (with deionised water) using different organic acids (lactic, citric and acetic). The thermal, structural and pasting properties, morphology and digestibility were evaluated and compared to the native starch. The enthalpy of the native maize starch ranged from 10.30 to 8.78 J g−1 after heat treatment with acetic acid. The starches treated by HMT using lactic and citric acids did not show gelatinisation peaks. The relative crystallinity also decreased after acid–heat treatment, while conventional HMT did not present significant difference in relation to the native starch. The peak viscosity for the native starch was 1,805.5 mPa s. After HMT with acetic and lactic acid, this figure was 969.5 and 41.5 mPa s, respectively. The treated maize starch by HMT with citric acid did not show viscosity peaks in the RVA profile. The morphology of the starches was not strongly affected by acid–heat treatment. HMT increased the RS content; the treatments with lactic and citric acid produced the highest values, with a fivefold increase in relation to the native maize starch (8.45%). The results indicate a possible application for acid–heat treatment starches in functional foods with reduced viscosity.