Effects of different edible oils on in vitro starch digestibility and physical properties of rice starch and rice flour

Amylose has the ability to form inclusion complexes with lipids and is resistant to enzymatic hydrolysis. This research aimed to explore the impacts of different healthy edible oils, i.e., coconut oil (CO), rice bran oil (RO), palm oil (PO), and soybean oil (SO) on the in vitro starch digestibility and physical properties of rice starch and rice flour. Each edible oil (10% w/w) was transferred to rice starch and rice flour and cooked at 95 C-degrees for 8 min. The contents of rapidly digestible starch and resistant starch in both cooked rice starch and rice flour were reduced and increased, respectively, by the addition of all edible oils, especially the CO and PO. The cooked rice starch and rice flour with added CO and PO had higher melting temperatures and dissociation enthalpies of the amylose-lipid complex (ALC) and V-type crystalline order than those with RO and SO inclusion. The results suggest that the high amounts of saturated fatty acids in CO and PO favour the formation of stable ALC, which limits the starch digestibility of cooked rice starch and rice flour. ALC products could be used as an alternative functional food ingredient to improve our health.

Automated summary

This research found that adding different types of healthy edible oils to rice starch and rice flour can reduce the content of rapidly digestible starch and increase the content of resistant starch. In particular, coconut oil and palm oil resulted in cooked rice starch and rice flour with higher melting temperatures and dissociation enthalpies of the amylose-lipid complex and V-type crystalline order.