Rice contains a large amount of starch. When rice is cooked, heat and water cause the starch granules to absorb water, swell and lose their original structure. This process, called gelatinisation, is what gives freshly cooked rice its soft, fluffy texture. Once the rice cools, however, the starch molecules gradually rearrange themselves and become more ordered. This is known as retrogradation. As the process continues, the rice becomes firmer, drier and more compact. Refrigeration can make this texture change particularly noticeable. It does not necessarily mean the rice has spoiled. It is largely a change in the starch structure. A study published in the National Library of Medicine found that cooling cooked white rice increases resistant starch, with the highest level after 24 hours at 4°C followed by reheating. This treatment also significantly reduced the glycemic response compared with freshly cooked rice in healthy adults.
