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Plants are a reservoir of phytochemicals, which are known to possess several beneficial health properties. Along with all the secondary metabolites, polyphenols have emerged as potential replacements for synthetic additives due to their lower toxicity and fewer side effects. However, controlling microbial growth using these preservatives requires very high doses of plant-derived compounds, which limits their use to only specific conditions. Their use at high concentrations leads to unavoidable changes in the organoleptic properties of foods. Therefore, the biochemical modification of natural preservatives can be a promising alternative to enhance the antimicrobial efficacy of plant-derived compounds/polyphenols. Amongst these modifications, low concentration of ascorbic acid (AA)–Cu (II), degradation products of ascorbic acid (DPAA), Maillard reaction products (MRPs), laccase–mediator (Lac–Med) and horse radish peroxidase (HRP)–H2O2 systems standout. This review reveals the importance of plant polyphenols, their role as antimicrobial agents, the mechanism of the biochemical methods and the ways these methods may be used in enhancing the antimicrobial potency of the plant polyphenols. Ultimately, this study may act as a base for the development of potent antimicrobial agents that may find their use in food applications.

Postharvest losses of whole and fresh-cut fruits and vegetables cause significant reductions in food availability and an increase in economic losses/damages. Additionally, regulatory agencies are increasingly restricting the postharvest use of synthetic chemicals. This has strengthened the need to develop environmentally friendly approaches to postharvest management, such as utilization of natural compounds, antagonist microorganisms, and treatments with abiotic stresses, among others. The current review focuses on the potential of low doses of abiotic stresses to extend the shelf life, increase the amount of health beneficial phytochemicals, and reduce postharvest losses of fresh produce. The positive effects of the responses to low doses of abiotic stresses are based on a biological phenomenon termed hormesis. Research to develop new technologies to improve postharvest handling of fresh fruit and vegetables as well as minimally processed products is critical. The phenomenon of abiotic stress hormesis in fresh fruit and vegetables shows the potential not only to enhance defense compounds that could reduce diseases during postharvest storage and extend shelf life but also to elevate the content of health-promoting substances. The beneficial effects of UV-C hormesis have been extensively investigated in numerous types of fresh produce. However, our knowledge on hormesis exhibited by other abiotic stresses is still limited. Hence, the objective of this review is to discuss the relevance of hormesis for postharvest research by examining whether all abiotic stresses exhibit the phenomenon, its biological significance, the potential application in various commodities, and how it may direct the future of postharvest research.

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Ozone and sulfur dioxide treatments can influence the expression patterns of PAL, chitinase and β-1,3-glucanase to different extents in different grape cultivars and under different exposure conditions. The upregulation of these genes may be involved in the mechanism by which these fumigants inhibit the decay caused by pathogenic fungi.

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Hydrogen peroxide (H2O2) is a reactive oxygen species (ROS) which participates in the signal transduction responses of plants toward biotic and abiotic stresses. Therefore, the objective of this study was to link the exposure of low doses of H2O2 to the improvement of the phytochemical composition of broccoli florets, in particular the content of glucosinolates (GLS), and hydroxy-cinnamates (HCA) without affecting the quality parameters of the vegetable. A dose of 1.25 mM H2O2 applied for 180 min was effective (hormetic) in maintaining the color of broccoli florets, which was also compared with a higher dose of 5.0 mM H2O2 applied for 180 min. The intensity of the treatments was related to respiration rate, which was monitored for 21 d at 4◦C along to weight loss. The initial respiration rate of florets exposed to both doses of H2O2 was significantly (p < 0.0001) higher relative to controls and resulted in weight loss in florets treated with the hormetic dose. The antioxidant capacity of florets, measured indirectly as Oxygen Radical Absorbance Capacity (ORAC) and ascorbic acid (AA), decreased in florets exposed to both doses. The concentration of glucobrassicins, aliphatic GLS, and HCA was consistently higher in florets treated with the two doses, compared to non-exposed florets. The enhancement of these compounds was accompanied by the over expression, immediately (6 h) after treatments, of tryptophan N-hydroxylase 2 (CYP79B3), dihomomethionine N-hydroxylase (CYP79F1), and phenylalanine ammonia-lyase (PAL) genes. Overall, the tested doses of H2O2 positively influenced the augmentation of indole-type and aliphatic GLS, as well as HCA in broccoli florets.