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Starch is considered an important ingredient in the preparation of safe food. Current study investigates the physicochemical, morphological, thermal and pasting properties of rice starches, subjected to HMT at 13 g/100 g moisture, at different treatment times (10, 30 and 60 min), directly in the grain paddy rice and in the isolated starch. HMT reduced extraction yield of rice starch with increasing HMT time. The HMT starches had lower gelatinisation enthalpy when compared to native starch. HMT in grain reduced extraction yield of starch by the alkaline method with increasing time of exposure to high temperatures, altering the structure of starch-protein. The HMT in grains decreases the setback of the isolated starches, due to amylose-lipid complexation induced by high temperatures applied on modification. The hydrothermal treatment increased the mechanical and thermal stability of rice starches and promoted the strengthening of links, forming a more stable structure.

Summary The effects of heat–moisture treatment (HMT) (120 °C for 10, 30 and 60 min) on paddy rice grains before parboiling, on head rice yield (HRY), pasting and thermal properties, and colour and cooking characteristics of parboiled rice were studied. The results indicated that the HMT performed intensifies the changes in grains after parboiling, impacting pasting and thermal properties, which results in rice kernels with yellowish colouration and greater cooking time. HMT increased the temperatures of gelatinisation, with increasing HMT time from 10 to 60 min and reduced the gelatinisation enthalpy. HMT also affected the pasting properties of rice flours, reducing setback and viscosity and increased their stability to heat and mechanical agitation. The HMT performed in rice grains before the parboiling process with 60 min of the treatment decreased the HRY and increased the level of metabolic defects only in the treatment with 60 min.