Steady/dynamic rheological characterization and FTIR study on wheat starch-sage seed gum blends

Abstract

In this study, the interactions of wheat starch (WS) (5%, w/w) with sage seed gum (SSG) (0–0.50%, w/w) were explored by steady and dynamic rheological tests and Fourier transform infrared (FTIR) spectroscopy measurements as well. Higher levels of SSG incorporation resulted in increase in limiting strain (γL, up to 137%), yield stress at the limit of the linear viscoelastic (LVE) range (τy, up to 852%) and flow-point stress (τf, up to 3083%) values. WS-SSG blends indicated an intermediate behaviour between a weak gel and a strong elastic gel (tan (δ) = 0.17–0.40). All blends exhibited shear-thinning and thixotropic flow behaviours, which were intensified at higher concentration of SSG. More SSG incorporation caused increase in the yield stress values achieved from the stress ramp method by 4308%. A bigger particle size was observed in the presence of 0.50% SSG. According to FTIR spectra, interactions between starch and SSG was promoted with increasing of SSG in the models. When SSG was added to starch, connection between water and –COO- groups resulted in the blocking of the interactions among SSG chains and amylose, and the interactions amid SSG chains. The changes in starch structure were assessed focusing on the intensity ratio of the bands at 1047 and 1022 cm−1 which represents the amount of ordered starch to amorphous starch. In the first and fifth days of storage, this ratio for control sample was higher than that of the samples containing SSG.