Effect of annealing treatment on physicochemical properties, rheology and in vitro digestion of potato starch-galactomannan complexes

Abstract

The effect of annealing treatment on the physicochemical properties, flow behavior, and especially in vitro digestibility of potato starch-galactomannan (locust bean gum, tara gum, guar gum, and fenugreek gum) complexes was investigated. Scanning electron microscopy and particle size analysis showed that the galactomannan (GTM) increased the size of potato starch (PS) and adhesions appeared in the starch-galactomannan complexes (PS-GTM). After annealing treatment (ANN), more adhesions appeared in the PS-GTM. However, ANN had little effect on the size of the PS and PS-GTM. GTM decreased the ΔH of the PS, and the short-range ordering (R 1047/1022), To, Tc, and Tp of the PS-GTM increased after ANN. Moreover, the diffraction pattern of the PS still was B-type after the addition of GTM and ANN. However, the relative crystallinity of the PS-GTM was decreased after ANN. Rheology showed that all the complexes exhibited elastic gel structures (G' > G″), and the addition of GTM increased the apparent viscosity, gel-like properties, and modulus of the PS. In vitro digestion showed that the addition of GTM increased the resistant starch (RS) content in the PS, and the RS was positively correlated with the ratio of mannose and galactose under the effect of ANN, with the RS content of the Tara gum complexes increasing from 69.73% to 89.42%. This study provides valid information for the development of healthy, low GI functional foods.