Effect of moisture content on cooking time of rice

Rice is the main food for nearly half of the world's population. Cooking of rice consumes more energy in households as well as in industries which use rice as an input material for preparing certain foods. In order to reduce the energy spent for cooking and to obtain perfectly and uniformly cooked rice, soaking before cooking is traditionally practiced in some countries. This paper depicts a study of soaking rice prior to cooking. The proposed method uses two models which describe the moisture level when soaking at room temperature less than the gelatinization temperature and the moisture transfer model at temperatures above gelatinization and therefore cooking the rice grain. The moisture movements through the rice grain when soaking and when cooking are developed using the non-linear moisture diffusion equation. Both models are solved numerically using a finite element package in an elliptical geometry which is adjustable depends on the type of the rice. The validity of the proposed model is verified by the good fit between the experimental and theoretical curves and it is observed that the non-linear diffusion equation is a better way to describe the moisture transfer model in a rice grain.