High resistant starch content in crossbred red rice and its downstream products

Resistant starch (RS) has drawn considerable attention over the past decade due to its positive physiological properties as well as accessibility in many starchy foods. RS is the starch portion resistant to enzymatic hydrolysis in the human gut. Increased levels of RS in rice grains lower the glycemic index (GI) value ensuring a negative correlation with amylose content (AC). UKMRC-9 is a cross-bred red rice with GI=46 and an intermediate AC has been clinically proven to decrease postprandial blood glucose after ingestion. The objective of this study was to investigate the RS contents for cooked UKMRC-9 and its downstream products in the form of RTE (ready-to-eat). With the intention to optimise the RS contents through retrogradation of starch, these cooked rice and rice-based products were subjected to cooked-freeze and thawed cycles to simulate the modus operandi of food manufacturing and food service industry. Applying a method of enzymatically degrading starch samples according to the Association of Official Analytical Collaboration (AOAC) International, a total of 8 samples of UKMRC-9 and its downstream products were analysed for their RS contents. Cooked and frozen UKMRC-9 with coconut oil, UKMRC-9 raw and red rice noodles were computed with the highest RS at 16.52 g/100 g, 14.24 g/100 g and 11.42 g/100 g, respectively. The red rice bread, wholegrain bread and Kueh Angku have a RS value of 4.99 g/100 g, 4.97 g/100 g and 3.12 g/100 g. Based on RS classification, the RS contents of the former and latter can be categorised as high and intermediate. This study showed that UKMRC-9 was a good source of RS on its own, additional cooking and freezing processes and using it as an ingredient will further enhance the RS content of the final food products.