A novel pumpkin seeds protein-pea starch edible film: mechanical, moisture distribution, surface hydrophobicity, UV-barrier properties and potential application

Abstract

The pumpkin seeds protein (PSP) films have good gas barrier properties and elongation at break, but their inferior tensile strength and high moisture adsorption needed to be overcome. There are few reports about modification of PSP films so far. This study was to investigate the effects of different ratios (0:5, 1:4, 1.5:3.5, 2:3, 2.5:2.5 and 5:0) of pea starch (PS)/ pumpkin seeds protein (PSP) on the morphology, mechanical properties, water vapor permeability (WVP), optical properties, hydrophobicity, and oil resistance of blend films. According to the results, the scanning electron micrographs of surface and cross-sections indicated the good biocompatibility between PS and PSP. The tensile strength was enhanced from 5.02 MPa to 16.41 MPa with the incorporation of PS at 40% level, but the elongation at break was decreased meanwhile. The addition of PS enhanced the hydrophobicity and reduced the swelling degree of films. And then, the composite films incorporated with PS were more transparent at visible region. The oil soaking had little effect on the mechanical properties of composite films with low starch content. The addition of starch led to the closer interaction between water molecules and macromolecules in film-forming matrix. In addition, the PS/PSP composite films showed inferior barrier properties of water vapor and ultraviolet light compared with pure PSP films. Based on the above various factors, the composite film composed of PS and PSP in a suitable proportion has the potential to package oily foods.