In vitro digestion, physicochemical and morphological properties of low glycemic index rice flour prepared through enzymatic hydrolysis

Low glycemic index (GI) rice flour was prepared through enzymatic hydrolysis. Slowly digestible and resistant starch contents increased significantly (p ≤ 0.05) by 195.82% and 204.03%, respectively, while as total, rapidly digestible and digestible starch contents decreased significantly (p ≤ 0.05) by 55.40%, 51.67%, and 18.74%, respectively, after enzymatic hydrolysis. Glycemic load of low GI rice flour was significantly (p ≤ 0.05) lower than untreated rice flour. The degradation temperature of low GI rice flour (~275°C) was lower compared to untreated rice flour (~298°C). Particle size distribution analysis indicated that both surface mean- D [3, 2] and volume mean diameter – D[4, 3] of low GI rice flour were higher than untreated rice flour. SEM results revealed numerous cracks in low GI rice flour whereas the surfaces of starch granules of untreated rice flour were smooth without scratches. Low GI rice flour presented A- and V-type polymorphs while as untreated rice flour showed only A-type crystallinity pattern.