In vitro starch digestibility of rice flour is not affected by method of cooking

- Cooking method had little effect on in vitro starch digestion in rice flours.
- Pressure cooking at low water content favored formation of amylose-lipid complex.
- Cooked waxy flour displayed less starch hydrolysis than cooked non-waxy flours.
- Viscosity of the gelatinized starch influenced in vitro digestion of cooked rice.

This study evaluated the effects of different cooking methods on in vitro starch digestibility of three rice varieties. Results from differential scanning calorimetry and X-ray diffraction of cooked rice flours showed that rice starch was completely gelatinized after cooking. The overall paste viscosities of cooked indica hybrid flour (IHF) and japonica flour (JF) were lower than those of their corresponding raw flours. However, cooked waxy flour (WF) showed much higher paste viscosities than raw flours, especially the viscosity at the start of RVA testing. Cooking increased greatly the rate and extent of starch digestion of IHF and JF, but had a small effect on WF. There were small differences in rate and extent of starch digestion of rice after cooking under various conditions. Cooking methods were found to have little effect on in vitro starch digestibility of rice. Viscosity of the gelatinized waxy starch matrix affected in vitro starch digestibility. This study enables us to gain a better understanding of cooking effects on in vitro digestibility of starch in rice flour.