A Multilayered Edible Coating to Extend Produce Shelf Life

In this study, a new edible coating material with enhanced mechanical and gas barrier properties was studied by coupling silk fibroin (SF) with poly(vinyl alcohol) (PVOH). SF and PVOH water suspensions were mixed at different ratios to form multilayered membranes that, after a phase separation, assembled on the surface of fresh-cut produce upon dip coating. The effects of the mixing ratio on transparency, mechanical properties, water vapor, and oxygen permeability of the films were investigated. Higher PVOH fractions corresponded to an increased ductility (increased elongation at break and decreased Young's modulus), which is essential for a food packaging material. A coating with SF:PVOH weight ratio 1:1 presented the minimum water vapor permeability and was selected to perform perishable food preservation studies. Weight loss and color changes of coated fresh-cut apples over 14 days of storage at 4 °C were significantly lower than those of uncoated controls. The addition of ascorbic acid to the coating material was also investigated to obtain an active food coating with oxygen scavenging properties. The obtained results demonstrated the ability of SF:PVOH blends to assemble into bilayered edible coatings that extend the shelf life of fresh-cut produce.