Edible Coatings Containing Oregano Essential Oil Nanoemulsion for Improving Postharvest Quality and Shelf Life of Tomatoes

Abstract

Edible coatings have attracted significant interest in maintaining quality and improving the shelf life of fresh fruit and vegetables. This study aimed to improve tomato storability by using edible coatings, based on alginate cross-linked with calcium chloride, and containing an oregano essential oil (OEO) nanoemulsion as a natural antimicrobial. The coating formulations were preliminary optimized in terms of alginate and calcium chloride concentrations, using response surface methodology, to obtain a thin (~5 µm) and uniform layer on the tomatoes surface. The optimized coating (prepared using sequential dipping in a 0.5% w/w sodium alginate solution and in a 2.0% w/w calcium chloride solution) was enriched by incorporating an OEO nanoemulsion, formulated with lecithin as a natural emulsifier, at an OEO concentration of 0.17% w/w in the alginate solution. The nanoemulsion did not significantly affect the coating thickness and uniformity but improved the wettability of the tomato skin. More specifically, the alginate-based edible coatings exhibited a strong interaction with the hydrophobic tomato skin surface (higher than water), promoting surface adhesion. The addition of OEO nanoemulsion in the coating, by providing more hydrophobic sites, further improved the wetting capability and adhesion of the coating solution on the tomato surface. The developed edible coatings successfully contributed to prolonging the tomato shelf life, by reducing the growth of the endogenous microbial flora (total microbial load, yeasts, and molds) over 14 days at room temperature in comparison with the control, with significantly better performances for the edible coating containing the OEO nanoemulsion.

Effect of Chitosan Coatings with Cinnamon Essential Oil on Postharvest Quality of Mangoes

“…When compared with other postharvest technologies, edible coatings have many advantages. They can form a protective layer on the surface of the mangoes, which can effectively block the epidermal pores and regulate the gas microenvironment around the mangoes, thus reducing water transpiration and oxidation caused by the amount of oxygen transmission, and maintaining the quality of mangoes [ 5 , 6 ].…”

NC‐1 coating combined with 1‐MCP treatment maintains better fruit qualities in honey peach during low‐temperature storage

“…Low‐temperature refrigeration is intended for temperature regulation to inhibit enzyme activity and reduce the intensity of cell respiration, thereby delaying the growth rate of microorganisms. Chemical inhibitors may usually delay fruit softening, reduce respiration peak and inhibit ethylene biosynthesis, such as 1‐methylcyclopropene (1‐MCP) (Shetty et al ., 2018; Sun et al ., 2018; Mendy et al ., 2019; Thakur et al ., 2019; Chen et al ., 2020; Pirozzi et al ., 2020).…”

Application of Encapsulation Technology in Edible Films: Carrier of Bioactive Compounds

“…Edible coatings incorporated with oregano essential oil nanoemulsion applied on tomato surface were found to have significant inhibitory action on the growth of spoilage microbes. However, these nanoemulsion-based edible coatings also retained the other quality characteristics of the tomatoes stored at ambient temperature conditions for more than 2 weeks (Pirozzi et al, 2020). Alginate-based edible coating encapsulating lemongrass essential oil applied on fresh-cut Fuji apples prevented the activity of Escherichia coli (Salvia-Trujillo et al, 2015).…”