Effect of processing on nutritionally important starch fractions in rice varieties

In the present study the effect of processing on starch fractions (rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch) were measured, using controlled enzymic hydrolysis with pancreatin and amyloglucidase, in six rice varieties; namely, BT rice, Gauri rice, Sona masoori, parboiled rice, Salem parboiled rice, and steamed rice. The processes studied were pressure cooking, boiling, steaming and straining. Rapidly available glucose (RAG) was also measured to derive a Starch Digestion Index (SDI). Cooking of rice by different methods decreased the amylose content. The degree of gelatinization ranged from 56 to 95, with pressure cooking resulting in the maximum degree. The starch fractions varied depending on the cooking method. Significant inverse correlations were seen between RDS and SDS (r = 0.40, P < 0.05), and between amylose and SDI (r = 0.60, P < 0.01). RAG and RDS related positively (r = 0.90, P < 0.01). The SDI of rice varieties cooked by the boiling and straining method were significantly higher (P < 0.05). The results emphasize that cooking methods influence the nutritionally important starch fractions in rice varieties.