Influence of parboiling and physico-chemical characteristics of rice on the glycaemic index in non-insulin-dependent diabetic subjects

Objective: To study the influence of parboiling, amylose content and gelatinisation temperature of rice on the postprandial blood glucose and insulin responses in non-insulin-dependent diabetic ((NIDDM) subjects. Design and subjects: Twelve NIDDM subjects ingested high (27%) and low amylose content five test meals of 50g available carbohydrates as white bread, cooked polished rice with high (27%) and low amylose content (12%), with different gelatinisation temperature and as non-parboiled and parboiled. The meals were taken in random order after a 12h fast with approximately 7 days interval. Results: The glycaemic indices (GI) of all rice varieties were lower than that of white bread (P <0.001). Furthermore, GI of parboiled rice with a high amylose content was lower than that of parboiled rice with a low amylose content (50 +/- 7 vs 73 +/- 7, P <0.01). No differences were observed between parboiled rice with high and low gelatinisation temperature (50 +/- 7 vs 47 +/- 4, n.s.), nor between non-parboiled and parboiled rice (50 +/- 7 us 53 +/- 7, n.s.). Insulin responses to the five test meals were not significantly different in the NIDDM subjects. Conclusions: In NIDDM subjects the investigated rices were all low glycaemic as compared to white bread, independent of parboiling and physico-chemical characteristics. The mild parboiling process used did not influence GI. The study showed that the amylose content, but not the gelatinisation temperature, may be an useful criterion in selection of low GI rices also after parboiling.