Effects of starch gelatinisation and water migration on the hardness of parboiled rice

Summary Parboiled rice is well known for its high nutritional value, while its firm texture is still challenging to accept by consumers. In this study, the effects of starch gelatinisation and water migration on the increased hardness of parboiled rice were investigated. The hardness of parboiled rice was affected by starch gelatinisation, displaying an increasing trend with an increasing degree of starch gelatinisation (DSG). Examination of the water migration characteristics during soaking showed that the water uptake capacity of parboiled rice was significantly enhanced. Compared to white rice soaked at 90 °C, the water molecules in parboiled rice were restricted to the outer layer of starch. Significant correlations between rice hardness, DSG and moisture absorption‐related parameters were established, indicating that gelatinised starch limits the migration of water to the inside of the rice kernel, resulting in a firm rice grain. These results enhance the understanding of starch gelatinisation by parboiling and water migration properties during the cooking process of parboiled rice. This study provided new insights into the regulation of hardness by parboiled rice processing.