Edible coating based on whey protein isolate nanofibrils for antioxidation and inhibition of product browning

Whey protein isolates (WPI) have been studied for film formation because of their favorable functional properties and industrial surplus; however, little is known regarding whey protein nanofibrils (WPNFs) as raw material for edible films. In the present study, WPNF-based edible coatings plasticized with glycerol (Gly) and trehalose (Tre) were studied. WPI (5%) can self-assemble into nanofibrils at 80 °C for 10 h under 220 rpm constant magnetic stirring. Compared with that of WPI, the hydrophobic and antioxidant activities of WPNFs were significantly increased. The microstructures and functions of WPI/Gly, WPNF/Gly, and WPNF/Gly/Tre films were characterized by scanning electron microscopy and atomic force microscopy, and by analyzing their contact angles, film thickness, transparency, moisture content, and solubility in water. Results showed that the formation of WPNFs increased surface smoothness, homogeneity, continuity, hydrophobicity, and transparency, and decreased the moisture content and water solubility of the films. To evaluate the performance of the edible coating, coated fresh cut apples were analyzed during storage. We found that the coatings containing WPNF (5%, w/v), Gly (4%, w/v) and Tre (3%, w/v) afforded the best protective action toward retarding the total phenolic content, browning, and product weight loss. Overall, the low cost, high biocompatibility, and consumer acceptance in taste tests support the ready application of these optimized WPNF films for commercial purposes.