Characterization of Sodium Alginate-Based Edible Active Coating Incorporated with Dendrobium officinale Polysaccharides and Its Application in Grape Packaging

In the present study, Dendrobium officinale polysaccharides (DOPs) are incorporated into sodium alginate (SA) for the development of SA-DOPs films. The physical, mechanical, and functional properties of SA-DOPs composite films and their ability to preserve fresh grapes are investigated. The results reveal that the addition of DOPs can significantly enhance the thickness, swelling ratio, tensile strength, elongation at break, and thermal stability of the films (p < 0.05) whereas the water solubility and water vapor permeability are decreased. Fourier transform-infrared (FT-IR) spectroscopy results reflect interaction of chemical groups and bonds between SA and DOPs. The result of scanning of electron microscopy (SEM) indicates smooth for SA-DOPs films while control film exhibits rough. The SA-DOPs films exhibit potential antioxidant effects on 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radicals. Furthermore, the composite films exhibit remarkable inhibition of the growth of Escherichia coli and Staphylococcus aureus (p < 0.05). In addition, the SA-DOPs coatings can effectively reduce weight loss, inhibit polyphenol oxidase activity, extend the shelf life of the grapes at room temperature (25 ± 1 °C) for 14 days. These results indicate that the SA-DOPs edible coatings might be a promising candidate in food preservation industries.