Effect of Storage Conditions on the Physicochemical Characteristics of Bilayer Edible Films Based on Iron Yam–Pea Starch Blend and Corn Zein

Abstract

Edible iron yam–pea starch-based bilayer films with a water and oil proof layer of corn zein were prepared by casting method and stored under normal temperature (25 °C; relative humidity (RH): 43%, 54%, 65%), refrigeration (4 °C) and freezing (−17 °C) for 150 days. The mechanical properties, scanning electron microscope (SEM) micrographs, oxygen and water vapor permeability, color, transmittance, haze, water content were systematically evaluated after 0, 30, 60, 90, 120 and 150 days. The transmittance, haze, and water content of bilayer films changed greatly within 150 days, which indirectly indicated the changes of the internal microstructure of the film matrix. The results were further verified by SEM analysis. Water and oxygen resistance gradually become worse. At 25 °C and 54% RH, the barrier performances were relatively strong. Films had relatively good tensile strength at normal temperature and high humidity, and relatively good elongation at break at low temperature and high humidity. SEM observation showed that there was no interlayer separation during storage. The internal network structure disappeared and reappeared again. The changes of internal microstructure also verified the changes of barrier and mechanical properties of bilayer films.