Extruded rice noodles: Starch digestibility and glycemic response of healthy and diabetic subjects with different habitual diets

High amylose rice variety was extruded to noodles and the starch digestibility and glycemic response of one healthy and two non-insulin dependent diabetic groups (Quezon City, Philippines and Toronto, Canada) with different habitual diets were determined. Rice extrusion significantly reduced the starch digestibility by 15% and the glycemic index in healthy volunteers by 36%. In both diabetic populations, the reduction in glycemic index was similar at 24%, suggesting that the effect was reproducible, and also that glycemic response was not affected by previous daily exposure of the subjects to rice. The effect of extrusion appears to be related to the starch gelatinization and retrogradation which occurred during processing as indicated by the lower amylograph viscosity and softer gel consistency of the rice noodles compared to the milled rice, as well as by the retrogradation test. The low glycemic response to high amylose rice and particularly the rice noodles suggests that these foods may have health benefits to both normal and diabetic individuals.