Effects of cooling methods on the cooling efficiency and quality of cooked rice

Rice is an important staple food, and often used in ready meals, which should be cooled rapidly after cooking. In the current research, cooked rice was cooled by vacuum cooling, air blast cooling, cold room cooling and plate cooling. It was found that vacuum cooling could chill the cooked rice with much shorter time but with higher weight loss than the other cooling methods. Vacuum cooling of the rice under different conditions could lead to changes of the cooling time and weight loss. If lower final pressure was used in the cooling process or less weight of cooked rice was vacuum cooled, shorter vacuum cooling time and lower weight loss could be obtained. If the rice was cooked for longer boiling time or was vacuum cooled with excess water, the cooled rice could have higher moisture content, but the cooling time would be prolonged significantly. Spraying water during vacuum cooling did not significantly prolong the cooling time, but increased the moisture content of cooled rice. On the other hand, longer boiling time, cooling with excess water and spraying water could reduce hardness of the cooled rice significantly. Only spraying of water could cause significant reduction in the adhesiveness of the rice.