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The aim of the present study was to investigate the effects of ethanol vapor on the inhibition of Alternaria alternata and Botrytis cinerea in postharvest blueberry and the induction of defense-related enzymes (DREs) activities in fungi-inoculated blueberries stored at 0±0.5°C for 16days. Results indicated that ethanol vapor markedly inhibited the mycelial growth of A. alternata and B. cinerea in a dose-dependent manner, with inhibition rates of 9.1% (250μlL−1), 36.4% (500μlL−1), and 5.5% (1,000μlL−1) on A. alternata and 14.2% (250μlL−1), 44.7% (500μlL−1), and 76.6% (1,000μlL−1) on B. cinerea , respectively. Meanwhile, ethanol vapor also enhanced the activities of DREs in fungi-inoculated blueberries, including β -1,3-glucanase (GLU), chitinase (CHI), phenylalnine ammonialyase (PAL), peroxidase (POD), and polyphenol oxidase (PPO). In particular, 500μlL−1 ethanol vapor increased the activities of DREs by 84.7% (GLU), 88.0% (CHI), 37.9% (PAL), 85.5% (POD), and 247.0% (PPO) in A. alternata -inoculated blueberries and 103.8% (GLU), 271.1% (CHI), 41.1% (PAL), 148.3% (POD), and 74.4% (PPO) in B. cinerea -inoculated blueberries, respectively. But, the activity of PPO was decreased by 55.2 and 31.9% in 500μlL−1 ethanol-treated blueberries inoculated with A. alternata and B. cinerea , respectively, after 8days of storage. Moreover, the surface structure and ultrastructure of 500μlL−1 ethanol-treated blueberry fruit cells were more integrated than those of other treatments. The findings of the present study suggest that ethanol could be used as an activator of defense responses in blueberry against Alternaria and Botrytis rots, by activating DREs, having practical application value in the preservation of postharvest fruit and vegetables. [ABSTRACT FROM AUTHOR]

BACKGROUND Blueberry is universally acknowledged as a kind of berry rich in antioxidants. Cold plasma, an emerging non‐thermal treatment technology, has been proved to be able to maintain or improve the antioxidant level while inactivating the microorganisms on the surface of fruits and vegetables. Postharvest blueberries were treated with atmospheric cold plasma (ACP; 12 kV, 5 kHz) for 0 s (Control), 30 s (ACP‐30), 60 s (ACP‐60), and 90 s (ACP‐90) in this study, and the effects of ACP on the antimicrobial properties, antioxidant activities, and reactive oxygen species (ROS) production were investigated during storage at 4 ± 1 °C for 40 days. RESULTS: Total aerobic bacteria and mold populations on ACP‐treated blueberries decreased significantly in a time‐dependent manner (P < 0.05), and decreased by 0.34–1.24 and 0.57–0.87 log10CFU g−1 respectively on ACP‐60‐treated blueberries during storage. The decay rate of blueberries was decreased by 5.8–11.7% and the decrease of blueberry firmness was slowed down by ACP‐60. But the total phenol, anthocyanin, and ascorbic acid contents increased, and superoxide dismutase, catalase, and peroxidase activities were enhanced in ACP‐treated blueberries. The free radical scavenging activity and total antioxidant capacity (T‐AOC) were enhanced. Hydrogen peroxide (H2O2) and superoxide anion (O2−) production rates declined by 27.3% and 41.3% at day 40 of storage, respectively. CONCLUSION: It is suggested that ACP may be a promising non‐thermal treatment technology for postharvest sterilization and preservation of blueberry under suitable conditions. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

• Ethanol vapor delayed the decline in firmness of postharvest blueberries. • Ethanol vapor delayed degradation of cell wall polysaccharides in blueberry. • Ethanol vapor inhibited activities of cell wall-degrading enzymes in blueberry. • Ethanol vapor delayed the disruption of the cell wall structure of blueberry. Blueberry fruit were treated with 500 μL L−1 ethanol for 18 h and then stored at 0 ± 0.5 °C with 90 % relative humidity (RH) for 40 d. The firmness, contents of cell wall polysaccharides, activities of cell wall-degrading enzymes (CWDEs), and cell wall ultrastructure in the blueberry fruit were determined during storage. The results showed that the decline in firmness of blueberries was delayed by ethanol vapor treatment during cold storage and shelf life, compared to the control. The contents of water-soluble pectin (WSP) and 4 % KOH-soluble fraction (4KSF) in ethanol-treated blueberries were reduced compared to those in the control. The contents of EDTA-soluble pectin (ESP), Na 2 CO 3 -soluble pectin (SCSP), 24 % KOH-soluble fraction (24KSF), and cellulose in ethanol-treated blueberries were higher than the control. The activities of pectin methylesterase (PME), polygalacturonase (PG), carboxymethyl cellulase (CMCase), β -glucosidase (β -Glu), β -galactosidase (β -Gal), α -galactosidase (α -Gal), and α -mannosidase (α -Man) in blueberries were suppressed by ethanol vapor treatment. However, there was no significant difference in the activity of α -arabinofuranosidase (α -Af) between ethanol-treated blueberries and the control. Moreover, ethanol vapor treatment delayed the destruction of the cell wall structure of the blueberry fruit via ultrastructural observations. Ethanol vapor treatment can retard the disassembly of cell wall polysaccharides by inhibiting CWDEs activities, thereby delaying blueberry softening. [ABSTRACT FROM AUTHOR]