Improvement the barrier and mechanical properties of whey protein isolate film using fructan obtained from Serish (Eremurus spectabilis) root as a novel polysaccharide

Abstract

In this study, we investigated the effect of fructan obtained from Serish root (Eremurus spectabilis) as a new film-base material in order to improve the barrier and mechanical properties of whey protein isolate (WPI) film. The effects of fructan (0, 50, 60, 70% v/v) and glycerol (Gly) (40 and 50% v/v) ratios on the mechanical, chemical, thermal, surface wetting, water vapor permeability (WVP), and morphological properties of WPI film were investigated. According to scanning electron microscope (SEM), the substitution of fructan to WPI significantly modified the surface properties of composite films, which had fewer cracks and pores compared to WPI films. The substitution of fructan decreased the water vapor permeability (6.64 × 10–6-1.85 × 10–6 g / m.s.pa) and increased the tensile strength (6.91–16.25 Mpa) and Young's modulus (30.84–42.84 Mpa) of the WPI film. Increasing the fructan content improved the mechanical properties and reduced the water vapor permeability of composite films. Fourier transform infrared (FTIR) spectra confirmed the formation of hydrogen bonding interactions between WPI and fructan. Differential scanning calorimetry (DSC) analysis exhibited a slight increase in the enthalpy values (81.43–154.3 J/g) with increasing fructan ratio of composite films, so that the thermal stability of WPI film improved due to stablishing more hydrogen bonds which also evidenced by FTIR. These results suggest that WPI 30 / Fructan 70 (40% Gly) can be considered as the best ratio for preparation of the composite film.