In-vitro digestibility, rheology, structure, and functionality of RS3 from oat starch

•Modified starches showed high contents of RS3 and good bile acid binding capacity.•Confirmational studies by SEM, XRD, ATR-FTIR and DSC.•Modified oat starches showed shear thickening behavior.

Starches isolated from three different varieties of oat were modified with dual autoclaving-retrogradation treatment to make modified food starches with high contents of type 3 resistant starch (RS3). FT-IR spectroscopy showed increase in the ratio of intensity of 1047 cm−1/1022 cm−1 on treatment. Morphology of the oat starches changed into a continuous network with increased values for onset temperature (To), peak temperature (Tp), and conclusion temperature (Tc). XRD showed an additional peak at 13° and increase in peak intensity at 20° inclusive of the major X-ray diffraction peaks which reflects formation of amylose–lipid complex from dual autoclaving-retrogradation cycle. Peaks at 13° and 20° are the typical peaks of the V-type pattern. Rheological analysis suggested that retrogradated oat starches showed shear thickening behavior as revealed from Herschel-Bulkely model and frequency sweep.