Extending the Postharvest Shelf Life of Strawberries Through a κ-Carrageenan/Starch-Based Coating Enriched with Zinc Oxide Nanoparticles

Abstract

The efficacy of an edible coating based on κ-carrageenan/cassava starch/zinc oxide nanoparticles (ZnONPs) on the postharvest quality of strawberries was studied over 9 days under environmental storage conditions. The Fourier Transform Infrared Spectroscopy (FTIR) spectra confirm the formation of semipermeable coatings loaded with ZnONPs (0, 1, 1.5, and 2%). The visual appearance of coated strawberries indicated nonmicrobial proliferation, while uncoated strawberries showed degradation after the third day. The weight loss outcomes suggest the lowest values for the κ75-1.5 (36.18%) compared to the control one (53.50%). The °Brix, pH, hardness, and color measurements support this. Principal Component Analysis (PCA) findings reveal that the κ75-1 and κ75-2 coatings maintained similar physicochemical quality, while κ75-1.5 maintained the greatest firmness (65% greater retention than the control). Furthermore, the absence of microbial colonies in the coated fruits corroborated the antimicrobial action of ZnONPs, confirmed by the inhibitory activity against Staphylococcus aureus, Salmonella typhimurium, and Escherichia coli. Thus, coatings containing ZnONPs proved effective in prolonging the quality of strawberries, preserving physicochemical properties, reducing postharvest losses, and contributing to more sustainable production and food security.