Effects of Cooking Processes on Physical Properties of Cooked Rice

Abstract

This study aimed to elucidate the effects of different cooking methods on physical properties of cooked rice by analyzing cooked rice and water in which the rice was cooked before and after boiling. Three rice cookers were used: pressure induction heating (IH-P), induction heating with steam injection (IH-S), and steam heating (ST). Cooked rice sampled from IH-S showed the highest weight and moisture content, followed by that from IH-P and ST. IH-S rice also exhibited a greater weight and moisture content both before and after boiling. The degree of starch gelatinization was approximately 90% across all the methods. Soluble solids on the rice surface were the lowest in ST. Sensory evaluation revealed that rice cooked using ST was harder, less sticky, and had more distinct grains, while rice cooked using IH-S was softer and moister. These results align with the weight and moisture content and reflect differences in the mechanisms of heating: the ST method uses steam, wherein water does not evaporate, whereas water evaporates when IH-P and IH-S cookers are used. IH-S promotes water absorption before boiling, thereby shortening cooking time and reducing evaporation.