Responses of Fresh-Cut Strawberries to Ethanol Vapor Pretreatment: Improved Quality Maintenance and Associated Antioxidant Metabolism in Gene Expression and Enzyme Activity Levels

Botrytis fruit rot management: What have we achieved so far?

Botrytis cinerea is a destructive necrotrophic phytopathogen causing overwhelming diseases in more than 1400 plant species, especially fruit crops, resulting in significant economic losses worldwide. The pathogen causes rotting of fruits at both pre-harvest and postharvest stages. Aside from causing gray mold of the mature fruits, the fungus infects leaves, flowers, and seeds, which makes it a notorious phytopathogen. Worldwide, in the majority of fruit crops, B. cinerea causes gray mold. In order to effectively control this pathogen, extensive research has been conducted due to its wide host range and the huge economic losses it causes. It is advantageous to explore detection and diagnosis techniques of B. cinerea to provide the fundamental basis for mitigation strategies. Botrytis cinerea has been identified and quantified in fruit/plant samples at pre- and post-infection levels using various detection techniques including DNA markers, volatile organic compounds, qPCR, chip-digital PCR, and PCR-based nucleic acid sensors. In addition, cultural, physical, chemical, biological, and botanical methods have all been used to combat Botrytis fruit rot. This review discusses research progress made on estimating economic losses, detection and diagnosis, as well as management strategies, including cultural, physical, chemical, and biological studies on B. cinerea along with knowledge gaps and potential areas for future research.

Responses of animals and plants to physiological doses of ethanol: a molecular messenger of hypoxia?

Our viewpoint is that ethanol could act as a molecular messenger in animal and plant organisms under conditions of hypoxia or other stresses and could elicit physiological responses to such conditions. There is evidence that both animal and plant organisms have endogenous levels of ethanol, but reports on the changes induced by this alcohol at physiological levels are sparse. Studies have shown that ethanol has different effects on cell metabolism at low and high concentrations, resembling a hormetic response. Further studies have addressed the potential cellular and molecular mechanisms used by organisms to sense changes in physiological concentrations of ethanol. This article summarizes the possible mechanisms by which ethanol may be sensed, particularly at the cell membrane level. Our analysis shows that current knowledge on this subject is limited. More research is required on the effects of ethanol at very low doses, in plants and animals at both molecular and physiological levels. We believe that further research on this topic could lead to new discoveries in physiology and may even help us understand metabolic adjustments related to climate change. As temperatures rise more frequently, dissolved oxygen levels drop, leading to hypoxic conditions and consequently, an increase in cellular ethanol levels.

Hydrogen Sulfide Enhances Browning Repression and Quality Maintenance in Fresh-Cut Peaches via Modulating Phenolic and Amino Acids Metabolisms

Effects of hydrogen sulfide (H₂S) on the browning and quality maintenance of fresh-cut peach fruit were studied. The results showed that H₂S treatment repressed the development of surface browning, suppressed the increase in respiration rate and weight loss, and delayed the decline of firmness while soluble solids content (SSC) and microbial growth were unaffected during storage. H₂S treatment maintained higher contents of phenolic compounds, especially neo-chlorogenic acid, catechin, and quercetin, and delayed the degradation of phenolic compounds by enhancing the activities of phenolic biosynthesis-related enzymes and inhibiting the oxidative activities of polyphenol oxidase (PPO) in comparison with control. Moreover, H₂S stimulated the accumulation of amino acids and their derivatives including proline, γ-aminobutyric acid (GABA), and polyamines (PAs) via enhancing biosynthesis and repressing degradation compared to control. These results suggested that H₂S treatment enhanced the accumulation of phenolic, amino acids, and their derivatives by modulating phenolic and amino acids metabolisms, which contributed to the higher antioxidant activity and membrane integrity maintenance, ultimately repressing browning development and maintaining the quality. Therefore, the current study speculated that H₂S might be a promising approach for browning inhibition and quality maintenance in fresh-cut peach fruit.

Effects of Ethanol Treatment on Storage Quality and Antioxidant System of Postharvest Papaya

Papaya is the fourth most favored tropical fruit in the global market; it has rich nutrition and can be used for medicine and food processing. However, it will soften and mature in a short time after harvest, resulting in a lot of economic losses. In this study, papaya fruits were soaked in 0, 12.5, 25, 50, and 100 ml/L ethanol solutions for 2 h and stored at 25°C for 14 days, by which we explored the effects of ethanol treatment in papaya after harvest. At an optimal concentration of ethanol treatment, color changing of the papaya fruits was delayed for 6 days, and decay incidence and average firmness of the fruits were shown as 20% and 27.7 N, respectively. Moreover, the effect of ethanol treatment on antioxidant systems in the papaya fruits was explored. It was observed that ethanol treatment contributed to diminish the development of malondialdehyde (MDA), ethylene, and superoxide anions. Furthermore, the activities of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) were promoted than those of control group, while the activities of peroxidase (POD), phenylalanine ammonia-lyase (PAL), and polyphenol oxidase (PPO) were brought down. In addition, the principal component analysis (PCA) showed that PAL, ethylene, and superoxide anions were the main contributors for the maturity and senescence of postharvest papaya. In this experiment, ethanol treatment had the potential of delaying the ripening and maintaining the storage quality of papaya fruits.

Effect of CaCl2 Treatment on Enzymatic Browning of Fresh-Cut Luffa (Luffa cylindrica)

Enzymatic browning is a major issue that reduces the commercial value of Luffa cylindrica during storage, processing, and transportation. Our results showed that 1% CaCl2 treatment was optimal for reducing the surface browning of fresh-cut luffa. After storage at 25 °C for four days, the treated luffa had a significantly higher total phenolic (TP) content than the untreated luffa. At the end of the storage period, the calcium treatment showed low malondialdehyde (MDA) and hydrogen peroxide (H2O2) accumulation in the luffa. The treated luffa maintained higher superoxide dismutase (SOD), catalase (CAT), and phenylalanine ammonia lyase (PAL) activities and lower polyphenol oxidase (PPO) activity as compared to the untreated luffa. Furthermore, the genes regulating SOD (e.g., SOD1, SOD2, and SOD3), CAT (e.g., LcCAT1 and CAT2), and PAL (e.g., PAL1 and PAL2) in calcium-treated luffa were upregulated to varying degrees, suggesting that Ca2+ inhibited the browning of fresh-cut tissue by regulating the activities of those enzymes. Ultrastructure images showed that the treated luffa could maintain the relative integrity of the cell membrane and organelles. Therefore, Ca2+ might act as a second messenger to reduce ROS oxidative damage and maintain the cell membrane integrity. This study provides new insights into the breeding of new luffa varieties that are resistant to browning and post-harvest treatments to reduce the browning of luffa tissue.

Effects of resveratrol treatment on quality and antioxidant properties of postharvest strawberry fruit

Strawberry fruit is one of people's favorite fruits. It has high nutritional value and health care effects. Strawberries lose their edible value quickly after being picked because of their thin skin, which is easily damaged. In order to find a method to maintain the quality of strawberries, the effects of resveratrol treatment on the nutritional quality and antioxidant metabolism of strawberry fruit were studied. The result indicated that 100 μM resveratrol was the optimal concentration to delay the occurrence of decay. Strawberry fruit treated with resveratrol delayed the decrease in firmness, total soluble solids (TSS), total phenolics content (TPC), total flavonoid content (TFC), vitamin C (Vc) content,1,1-diphenyl-2-picrylhydrazyl (DPPH), and 2,2'-azino-bis (3-ethylbezothi- azot-hiazoline-6-sulfonic acid) (ABTS) radical scavenging capacities. The malondialdehyde (MDA) content, hydrogen peroxide (H₂ O₂ ) content, and superoxide anion (O₂ ^•- ) production of control fruit were significantly higher than those of treated fruit. Strawberry fruit treated with resveratrol also increased the activities of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) during storage. Therefore, resveratrol has been proved to effectively improve the nutritional quality and antioxidant properties of strawberry fruit. PRACTICAL APPLICATIONS: Strawberry fruit is rich in nutrients, which is beneficial to human health. But strawberry fruit has high water content and soft tissue, which is easy to be damaged and decayed. Therefore, it is particularly important to find a way to maintain strawberry fruit quality. In this study, resveratrol has good antioxidant, health care, and antibacterial properties. Resveratrol treatment can maintain the nutritional quality of strawberry fruit and can be used as an effective method for strawberry fruit preservation.

Effect of ethanol fumigation on pericarp browning associated with phenol metabolism, storage quality, and antioxidant systems of wampee fruit during cold storage

Wampee fruit is a popular fruit cultivar in South-East Asia due to its high levels of nutrients and antioxidants; however, pericarp browning leads to a short storage life with great economic loss during years. The purpose of this work was to determine whether postharvest ethanol fumigation affected pericarp browning development of wampee fruit during 12 days of storage at 8 ± 0.5°C, and if so, how it is related to phenol metabolism and how it affects quality attributes and antioxidant systems during storage. After fruits were fumigated with 100, 300, 500, and 800 μl/L for 5 hr at 22 ± 0.5°C, ethanol significantly reduced the development of pericarp browning by increasing total phenolics (TP) content and decreasing the activity of polyphenol oxidase (PPO), especially in 500 μl/L ethanol treatment. Additionally, ethanol delayed the losses in fruit firmness (FF), soluble solid content (SSC), and titratable acidity (TA), retarded weight loss and accumulation of malondialdehyde (MDA) content and maintained relatively high contents of ascorbic acid (AsA), total flavonoids (TF), and total antioxidant capacity (TAC) and activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD). In conclusion, results demonstrated that postharvest ethanol fumigation in wampee fruit has ability to reduce pericarp browning development by regulating phenol metabolism and enhancing antioxidant systems.

Nanocomposite packaging regulates extracellular ATP and programed cell death in edible mushroom (Flammulina velutipes)

Our previous study indicated that nanocomposite packaging material (Nano-PM) containing nano-Ag, nano-TiO₂, nano-SiO₂ and nanoattapulgite alleviated postharvest senescence of Flammulina velutipes by regulating respiration and energy metabolism. In this study, extracellular ATP (eATP) and programmed cell death (PCD) were employed as critical factors to further investigate the senescence mechanism of postharvest F. velutipes. Results demonstrated that Nano-PM delayed apyrase activity decrease and stimulated critical oxidative phosphorylation-related gene expression to inhibit eATP content increase, which is a crucial signaling molecule related to delaying senescence. The regulation of eATP resulted in alleviating PCD including chromosomal concentration, DNA fragmentation, Ca²⁺ influx, high caspase-1 activity and cytochrome c content and leading to high cell viability. Overall, Nano-PM alleviated PCD and postharvest senescence of F. velutipes by regulating extracellular ATP.

Physiological and Metabolomic Analysis of Cold Plasma Treated Fresh-Cut Strawberries

Cold plasma technology offers new opportunities to the decontamination and preservation of fruits and vegetables. In the present research, strawberries were cut into four wedges and then treated with dielectric barrier discharge plasma at 45 kV for 1 min and stored for 1 week (4 °C). Metabolomic analysis suggested that plasma treatment improved the biosynthesis of the metabolites in the "flavones and flavonol biosynthesis" pathway and "biosynthesis of phenylpropanoids" pathway in fresh-cut strawberries. Physiological assay demonstrated that plasma treatment maintained the texture properties and inhibited microbial growth of fresh-cut strawberries. In addition, plasma treatment also promoted the accumulation of total phenolics, total flavonoid, and anthocyanin by enhancing the critical enzyme activities and activating related gene expression in phenylpropanoid as well as reactive oxygen species metabolism, which contributed greatly to the enhancement of antioxidant capacity of strawberry wedges. Our investigation provided a new perspective of the effect of plasma treatment on the safety and quality of strawberry wedges and suggested that cold plasma treatment holds promise as an emerging processing technology for improving the quality and antioxidant activity of postharvest fruits and vegetables.