Development of novel bio-based methods for inhibition of plant pathogens

Abstract

In this thesis, to develop a post-harvest bio-based preservation method for spoilage of fresh fruits and vegetables, antimicrobial packaging commonly applied for inhibition of human pathogenic bacteria was adapted for inhibition of plant pathogenic bacteria including Pseudomonas syringae, Erwinia amylovora, Xanthomonas vesicatoria and Erwinia carotovora. The zein based films were developed by incorporation of pure phenolic acids such as gallic acid (GA), cinnamic acid (CA), vanillic acid (VA); essential oils such as carvacrol (CAR), thymol (THY), eugenol (EUG) and citral (CIT) and phenolic extracts obtained from clove, artichoke, oregano and walnut shells into film forming solutions. The films containing phenolic acids between 1 and 4 mg/cm2 were effective on all bacteria. Essential oils at concentrations between 2 and 4 mg/cm2 and clove extract at concentrations between 4 and 8 mg/cm2 were found effective against pathogens except P. syringae. The HPLC analysis showed that the clove extracts owe its inhibitory activity to high concentration of GA which is a potent antimicrobial. The incorporation of natural compounds and extracts into films caused significant changes in morphologies and mechanical properties of films. This thesis showed the good potential of antimicrobial films against plant pathogens for the first time in the literature.