Effects of in-package atmospheric cold plasma treatment on the qualitative, metabolic and microbial stability of fresh-cut pears.

BACKGROUND: The greatest hurdle to commercial marketing of fresh-cut fruits and vegetables is limited shelf life due to microbial hazards and quality deterioration. Atmospheric cold plasma (ACP) is an emerging non-thermal technology with significant potential to improve the safety and storability of fresh products. The objective of this study was to evaluate the effects of ACP, generated in sealed packaging, on the qualitative, metabolic and microbial stability of fresh-cut pears during simulated cold storage. RESULTS: ACP treatments were effective in inhibiting the growth of mesophilic aerobic bacteria, yeast and mold, particularly CP3 (65 kV, 1 min), which could prolong shelf life to the greatest extent. While decontamination was not always associated with an increase in plasma intensity. Moreover, at 65 kV for 1 min, ACP treatment had the potential to retard respiration, and maintain organoleptic properties and other quality attributes. Additionally, peroxidase and pectin methylesterase (PME) activities were reduced immediately after treatments. These effects were dependent on treatment voltage and time, while a subsequent recovery in activity was only observed for PME. CONCLUSION: The results obtained from this study will contribute to an understanding of the effects of in-package ACP treatments on the storability and microbial safety of fresh-cut pears. This knowledge could be beneficial in reducing quality losses for fresh-cut pears and the preservation of other products. © 2021 Society of Chemical Industry.

Control of postharvest soft rot caused by Erwinia carotovora of vegetables by a strain of Bacillus amyloliquefaciens and its potential modes of action.

Erwinia carotovora subsp. carotovora (Ecc), the causal agent of bacterial soft rot, is one of the destructive pathogens of postharvest vegetables. In this study, a bacterial isolate (BGP20) from the vegetable farm soil showed strong antagonistic activity against Ecc in vitro, and its twofold cell-free culture filtrate showed excellent biocontrol effect in controlling the postharvest bacterial soft rot of potatoes at 25 °C. The anti-Ecc metabolites produced by the isolate BGP20 had a high resistance to high temperature, UV-light and protease K. Based on the colonial morphology, cellular morphology, sporulation, and partial nucleotide sequences of 16S rRNA and gyrB gene, the isolate BGP20 was identified as Bacillus amyloliquefaciens subsp. plantarum. Further in vivo assays showed that the BGP20 cell culture was more effective in controlling the postharvest bacterial soft rot of green peppers and Chinese cabbages than its twofold cell-free culture filtrate. In contrast, the biocontrol effect and safety of the BGP20 cell culture were very poor on potatoes. In the wounds of potatoes treated with both the antagonist BGP20 and the pathogen Ecc, the viable count of Ecc was 31,746 times that of BGP20 at 48 h of incubation at 25 °C. But in the wounds of green peppers, the viable count of BGP20 increased 182.3 times within 48 h, and that of Ecc increased only 51.3 %. In addition, the treatment with both BGP20 and Ecc induced higher activity of phenylalanine ammonia-lyase (PAL) than others in potatoes. But the same treatment did not induce an increase of PAL activity in green peppers. In conclusion, the present study demonstrated that the isolate BGP20 is a promising candidate in biological control of postharvest bacterial soft rot of vegetables, but its main mode of action is different among various vegetables.