Thermal and physicochemical properties of rice grain, flour and starch

Three types of rices, namely, Thailand rice (Indica), Nipponbare (Japonica) , and Himenomochi (Japonica waxy), in grain, flour, and starch forms have b een studied for their thermal and physicochemical properties. In grain form , Indica was slender and Japonica rices were bold and thick. Indica had the highest protein and amylose equivalent. Protein contents in isolated starc hes varied from 0.2 to 0.9%. Cooked Indica grain was hardest and waxy rice was softest; stickiness was highest in Japonica rice. Glass transition temp erature (Tg) was highest in Indica rice flour (similar to 222 degrees C) an d almost the same in Japonica rice flours. Melting point was highest for Ja ponica (similar to 264 degrees C) and almost the same for Japonica waxy and Indica rice flours. Tg values of starches were almost the same in Indica a nd Japonica waxy (similar to 287 degrees C); defatting caused reduction in this property in all of the starches. Highest melting point was shown by In dica starch (similar to 276 degrees C) and was almost the same for the othe r two starches. Protein and fats play a critical role in glass transition a nd melting points of rice flours and their respective starches. Viscosities of the cooked pastes of flour and starch during cooking in an RVA instrume nt and their gel and other properties have been discussed.