Comparative studies on the physicochemical properties and microstructure of raw and parboiled rice

The protein and mineral salts of rice were found to have increased while water-soluble substances were found to have decreased as a result of parboiling. Parboiling resulted in marked changes in the amylograph properties of rice paste, as well as increasing its resistance to alkali dispersion. The grains were shorter but wider, with lower water absorption and swelling capacity during cooking than those of raw-milled rice.The differences in ultrastructure between dry and cooked raw-milled and parboiled rice were studied with a scanning electron microscope. Complete deformation of the starch granules was evident in the raw-milled rice after cooking for 9 × 10² and 12 × 10² s, while those of parboiled rice showed great resistance to deformation. Variations in the over-cooked grains of both raw-milled and parboiled rice were studied.