SUSCEPTIBILITY OF STARCH TO IN-VITRO ENZYME HYDROLYSIS IN RICE, RICE FLAKES AND INTERMEDIARY PRODUCTS

The susceptibility of starch to in vitro hydrolysis by different enzym es was studied in raw rice, flaked rice and intermediary products obta ined at various stages during processing of rice to flakes Starch hydr olysis was lowest namely 100 to 370 g/kg, in raw rice but increased to 410 to 870 g/kg after processing and up to 100% after cooking, depend ing on the enzymes used and the assay conditions selected. Starch degr adation was maximal after treatment with pancreatin followed by amylog lucosidase and less; by alpha-amylase. However, addition of pepsin inc reased the susceptibility of starch hydrolysis indicating that a fract ion of starch might be complexed with protein. This appeared to be the case with flakes obtained by single pressing in a heavy duty cereal r oller flaker rather than those produced by repented gradual pressing i n an edge-runner. Conditions favourable for starch retrogradation and also deep-fat frying of flakes reduced the susceptibility of starch to enzyme hydrolysis. Heat treatment of moist paddy (rice) and mechanica l damage during flaking increased the availability of starch bl rice t o enzymic hydrolysis. A parr of starch got complexed with protein, the reby partly decreasing its susceptibility to hydrolysis.