Meta-analysis and comparative study of different oils and cooking methods on glycemic response of brown and white rice

Lian, Yun Ping (2025) Meta-analysis and comparative study of different oils and cooking methods on glycemic response of brown and white rice. Master dissertation/thesis, UTAR.

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Abstract

Rice, a staple food, has a high glycemic index (GI), contributing to adverse metabolic health outcomes. To mitigate this, different processing technologies and cooking methods have been developed to alter starch proportions, including rapidly digestible (RDS), slowly digestible (SDS), and resistant starches (RS). Retrogradation, achieved by cooling cooked rice, recrystallises gelatinised starch into a more resistant form. Additionally, incorporating oils to rice during cooking forms amylose-lipid complexes (ALC), slowing glucose release. However, the combined effects of retrogradation and oil treatments on nutritional composition and glycemic response remain underexplored. This study examined the impact of palm oil (PO) and coconut oil (CO) on the starch profile of brown and white rice using three cooking methods (A: stir-frying raw rice with oil before steaming, B: adding oil to cooking water during steaming, C: stir-frying steamed rice with oil), followed by refrigeration at 4°C for 12 hours. A meta-analysis showed that retrogradation significantly (p<0.05) increased RS and decreased RDS in white rice. Proximate analysis revealed changes in moisture, crude fat, and carbohydrate content across treatments. Brown rice with both oil treatments showed the lowest release of glucose across three cooking methods. Both oil treatments demonstrated a reduction in the RDS and an increase in the RS in both rice across three cooking methods. A greater integrity of swollen starch granules was observed in oil-treated rice across all cooking methods via scanning electron microscopy. Additionally, the indigestible RS demonstrated prebiotic potential by promoting the growth of Lacticaseibacillus casei and Lacticaseibacillus rhamnosus while reducing oligosaccharides over 24 hours. CO-treated white rice prepared using Method A showed the greatest probiotic growth. These findings highlight the potential for oil treatments and retrogradation to reduce the glycemic response of rice while improving gut health, addressing a critical research gap and offering practical dietary strategies for metabolic health management.

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