Effect of rice ageing and freeze-thaw cycle on textural properties of cooked rice (Oryza sativa L.) cv. Khao Dawk Mali 105



This study investigated the effect of rice grain ageing (0.7–12 months) and freeze-thaw 1–5 cycles on the textural properties of cooked rice. The cooked rice from aged rice grains was freezing and thawing up to five cycles. Ageing of the rice grain increased the hardness and decreased the stickiness of the cooked rice. Repeated freeze-thaw cycles caused an increase in hardness and a decrease in stickiness of aged cooked rice. Scanning electron micrographs showed a rough surface on the cooked rice after repeated freeze-thaw cycles, especially for cooked rice from rice aged for 12 months. Differential scanning calorimetry and X-ray diffraction showed increased starch retrogradation with increased freeze-thaw cycles. The gelatinisation temperature and gelatinisation enthalpy increased when rice was aged for longer periods. Thus, ageing of rice and the number of freeze-thaw cycles influence the textural properties of cooked rice.