Dual enzyme modified oat starch: Structural characterisation, rheological properties, and digestibility in simulated GI tract

Oat starches from three different varieties were treated with combination of β-amylase and transglucosidase and their structural, rheological, thermal, and digestibility through simulated GI tract conditions were investigated. By dual enzyme modification, the granules form a discontinuous compact fibrous structure with many surface cracks. The transformation from A-type to A + V type pattern with decrease in crystallinity was observed in dual enzyme modified starches. The ratio of intensity, 1047/1022 cm−1 and 995/1022 cm−1 of enzyme modified starches were reduced compared to their native ones as revealed from FTIR spectra. The resistant starch (RS3) content was increased to 35.81-48.88% from 17.14-23.9%. The viscosity of starches decreased on enzymatic treatment, exhibited shear-thinning behavior as reflected from the convex shaped graph. Also, dual enzyme treatment of starches resulted in significant decrease in amount of glucose release for Sabzaar than SKO20 and SKO90. The increase of RS observed in this study is associated with enhanced branch density and RS3 crystallites.