Potential application of natural phenolic antimicrobials and edible film technology against bacterial plant pathogens

Abstract

In this study, antimicrobial edible film technology used frequently for inhibition of human pathogens in processed food was employed as a postharvest bio-based preservation method to prevent bacterial spoilage of fresh fruits and vegetables. Antimicrobial edible zein films were developed by incorporation of pure phenolic acids (PAs) such as gallic acid (GA), cinnamic acid (CA), vanillic acid (VA); essential oils (EOs) such as carvacrol (CAR), thymol (THY), eugenol (EUG) and citral (CIT) and phenolic extract (PE) from clove. In order to test synergetic effect of PAs, different amounts of PAs were added into film solution to obtain films containing mixture of GA and CA, GA and VA, CA and VA at different concentrations. The antimicrobial performances of edible films were tested on selected plant pathogenic bacteria including Pseudomonas syringae, Erwinia amylovora, Xanthomonas vesicatoria and Erwinia carotovora. The overall results of antimicrobial tests showed that films containing PAs between 1 and 4 mg cm-2 inhibited all pathogens while EOs at concentrations between 2 and 4 mg cm-2 and clove extract between 4 and 8 mg cm-2 were found effective against pathogens except P. syringae. Morover, the incorporation of combination of different PA showed greater inhibitory activity on plant pathogens than incorporation of a single PA into films. The edible zein coatings have already been applied for coating of fresh fruits and vegetables at the postharvest stage to suppress their respiration rate and prolong their refrigerated storage. This work clearly showed the benefit of incorporating a single or mixture of antimicrobial phenolic compounds, EOs and PEs in edible zein films against bacterial plant pathogens. The developed films might be employed against plant pathogens by coating fresh fruits and vegetables, seeds, seedlings, tree stems, soil as well as agricultural tools and constructions without using toxic chemicals. © 2020 International Society for Horticultural Science. All rights reserved.