1-Methylcyclopropene treatment delays the softening of Actinidia arguta fruit by reducing cell wall degradation and modulating carbohydrate metabolism

Generative adversarial network integrated with metabolomics identifies potential biomarkers related to quality changes of atemoya (Annona cherimola × Annona squamosa) stored at 10 and 25 °C

Atemoya fruit deteriorates rapidly during post-harvest storage. A complete understanding of the metabolic mechanisms underlying this process is crucial for developing effective preservation strategies. Metabolomic approaches combined with machine learning offer new opportunities to identify quality-related biomarkers. This study compared atemoya quality stored at 25 °C and 10 °C using untargeted metabolomics integrated with generative adversarial network (GAN) and random forest (RF) analysis. It was found that GAN successfully amplified the metabolomic dataset 10-fold, enabling robust RF-based identification of 20 quality change-related biomarkers. These biomarkers were primarily involved in energy metabolism, reactive oxygen species regulation and primary metabolic pathways including amino acids, lipids and carbohydrates. Low-temperature storage inhibited respiration, preserved cell structure and altered specific glycerophospholipid metabolic pathways. These findings provide molecular insights into low temperature preservation mechanisms and establish a novel framework for metabolomic data analysis in postharvest research.

The transcription factors AdNAC3 and AdMYB19 regulate kiwifruit ripening through brassinosteroid and ethylene signaling networks

The pivotal role of ethylene (ETH) in fruit ripening has been extensively studied; however, the function of brassinosteroids (BRs) in regulating fruit ripening remains poorly understood. Specifically, the mechanism by which BRs interact with ETH to affect kiwifruit (Actinidia deliciosa) ripening is unclear. Our research showed that 2 genes encoding transcription factors, AdNAC3 and AdMYB19, and the fruit softening gene AdEXP3 (encoding a cell wall expansion protein, expansin 3) were upregulated by ETH and downregulated by BRs. Furthermore, AdNAC3 and AdMYB19 positively regulated the activity of the AdEXP3 promoter, and AdNAC3 positively regulated the promoter activity of AdMYB19. The physical interaction between AdNAC3 and the B-box-type zinc finger protein AdBBX32 affected fruit ripening. Transient overexpression and silencing experiments revealed that ETH upregulated and BRs downregulated the expression of AdNAC3 and AdMYB19, thereby regulating the expression level of AdEXP3 and participating in pectin degradation. Stable transformation of AdNAC3 in tomato fruits accelerated fruit color change and promoted fruit ripening. These results indicate that AdNAC3 and AdMYB19 are involved in the hormone interaction between BRs and ETH in regulating kiwifruit ripening, providing insights into the molecular mechanisms underlying the crosstalk between BRs and ETH.

γ-Aminobutyric acid treatment enhances quality and improves antioxidant activities of fresh-cut Euryale ferox stems during postharvest storage

Introduction

Fresh-cut Euryale ferox stem (FCEFS) is a nutrient-rich but underutilized vegetable that has a short shelf life, making it prone to softening and rotting.

Methods

The effects of different concentrations of γ-aminobutyric acid (GABA) on sensory quality and antioxidant activity during cold storage at 4°C for 20 d were examined.

Results

The results revealed that the FCEFS samples treated with 5 mM GABA maintained greater hardness and ascorbic acid, total phenolic compound and chlorophyll contents than the FCEFS samples not treated with GABA. FCEFS samples subjected to GABA treatment and stored under long-term cold storage conditions presented elevated sensory scores. The control group had ceased to possess commercial value on 16 d, and it was edible by 20 d following GABA treatment, which was corroborated by the notable colour characteristics and electronic nose analysis. Notably, GABA treatment delayed the decrease in soluble solid and endogenous GABA levels, and delayed the accumulation of malondialdehyde and the increase in lignin content in FCEFS during cold storage. In addition, GABA maintained high peroxidase (POD), superoxide dismutase (SOD), ascorbate peroxidase (APX) and phenylalanine ammonia lyase (PAL) activities.

Discussion

Treatment with 5 mM GABA maintained the shelf-life and sensory quality of the FCEFS for 20 d at 4°C. Therefore, these results indicate that GABA can be used to delay the softening of FCEFS and extend its cold storage and shelf-life.

Melatonin treatment delayed fruit softening by regulating postharvest carbohydrate metabolism of hami melon

Melatonin (MT) treatment has been proven to improve fruit quality. Herein, the efficacy of 0.5 mmol L-1 MT treatment on carbohydrate metabolism, fruit softening, and their relationship during storage of harvested Hami melons was investigated. The results indicated that compared with those in control group, MT treatment markedly delayed fruit softening and the total soluble solids/titratable acid ratio, inhibited cell wall polysaccharide degradation, and maintained the cell wall integrity in Hami melons. Besides, MT treated also increased the starch, sucrose, and sorbitol contents, enhanced sucrose phosphate synthase and sucrose synthase synthesis activities, whereas reduced pectin methyl esterase, polygalacturonase, cellulase, β-galactosidase, β-glucosidase, xyloglucan endotransglycosylase, amylase, sucrose synthase-cleavage, acid invertase, neutral invertase, sorbitol oxidase, NAD-sorbitol dehydrogenase, NADP-sorbitol dehydrogenase activities in Hami melons. Additionally, MT treatment downregulated the expression levels of CmPG, Cmβ-gal, CmAmy, CmAI, CmNI and CmSOX, and upregulated the expression of CmSPS. Collectively, MT could slow fruit softening and prolong its shelf life by regulating carbohydrate metabolism.

VvARF19 represses VvLBD13-mediated cell wall degradation to delay softening of grape berries

Fruit softening directly impacts its storage life, transportability, and customer acceptance. Auxin plays a key role during fruit ripening, but the underlying mechanisms of how auxin regulates fruit softening remain unclear. In this study, we investigated the regulatory roles of auxin on berry cell wall degradation during grape (Vitis vinifera L.) softening. During grape berry development, berry firmness and auxin content both firstly increase and then decrease, and peaks occur 4-6 weeks after full blooming. Exogenous NAA (α-naphthalene acetic acid, a synthetic auxin) treatment inhibits berry softening by delaying propectin, cellulose, and hemicellulose degradation, which maintains cell wall integrity in the grape flesh. Weighted gene co-expression network analysis (WGCNA) showed that VvLBD13, correlated with VvARF19, could be a key gene in this delaying of berry softening, and is involved in auxin signal transduction and cell wall degradation metabolism. Overexpression and transient overexpression of VvLBD13 in tomato or in grape berry indicate that VvLBD13 accelerates hemicellulose degradation by binding the promoters of VvXTH10 (xyloglucan endotransglucosylase/hydrolase 10) and VvEXPLA1 (expansion-like A1), which results in rapid softening after veraison. Collectively, this research furnishes an exhaustive understanding of the auxin-driven regulatory mechanisms of grape berry softening.

Caffeic acid enhances the postharvest quality by maintaining the nutritional features and improving the aroma volatiles for nectarine fruit

Maintaining the quality of postharvest nectarine fruit is considerably challenging owing to their vigorous metabolism processes. This study explored the effectiveness of the natural preservative caffeic acid in extending the shelf-life and improving the flavor quality of nectarine. The decay rate of caffeic acid-treated fruit was only 40.00 % but 73.33 % in control group at the end of storage. Other results showed that caffeic acid inhibited fruit quality deterioration, reflected in weight loss, peel color, pulp softening, respiration rate, malondialdehyde accumulation and ethylene biosynthesis. Findings might be attributed to increased levels of antioxidant compounds, such as ascorbic acid, simple phenols and flavonoids, which maintained high antioxidant capacity and metal reducing power of fruit cells. Notably, the content of phenolics was maintained at 241.11 mg kg-1 in caffeic acid-treated fruit by 8 d, which was only 138.21 mg kg-1 in control. Importantly, nectarine treated with caffeic acid possessed a suitable sugar-to-acid ratio, imparting the fruit with an excellent taste. Additionally, caffeic acid facilitated the effective release of esters and lactones, especially γ- and δ-decalactone with fruity aroma, and prevented green aroma and alcoholic off-flavor. The level of lactones in caffeic acid-treated fruit reached 126.76 μg kg-1 during mid-storage, giving the fruit an attractive flavor quality, while was only 50.61 μg kg-1 in control. Overall, caffeic acid exhibited the potential to preserve the quality of nectarine, ensuring both nutritional and edible value for fruit.

1-Methylcyclopropene Delays Browning and Maintains Aroma in Fresh-Cut Nectarines

The color and aroma of nectarines experience adverse effects from cutting, resulting in the fast senescence of fruit tissue. Therefore, 1-methylcyclopropene (1-MCP) was used to treat postharvest nectarines before cutting, and its effect on the surface browning and aroma alteration were investigated. The results indicated that 1-MCP restrained the soluble quinone (SQC) accumulation in fresh-cut nectarines by regulating the peroxidase (POD) and polyphenol oxidase (PPO) activities and the metabolism of phenolic compounds. Compared with the control, 1-MCP pre-cutting treatment maintained the ultrastructural integrity of the cell wall in fresh-cut nectarines, which also showed reduced malondialdehyde (MDA) content and reactive oxygen species (ROS) and enhanced the 1,1-Diphenyl-2-Picrylhydrazyl (DPPH) radical scavenging activities. Electronic nose and GC-MS analysis revealed that the aroma profiles presented significant differences in the control and 1-MCP treatment during the storage at 0 °C for 10 days. The browning value of the 1-MCP pre-cutting treatment was 29.95% lower than the control, which prevented the loss of aroma on day 10. The fresh-cut nectarines could still maintain the characteristic flavor, while the flesh maintains its firmness. The 1-MCP pre-cutting treatment improves the sensory and aroma characteristics of fresh-cut fruits, which is beneficial to the preservation of fresh-cut fruits, improves transportation efficiency, and then improves the overall quality and market attractiveness of the fruit.

DNP and ATP modulate the pulp softening and breakdown in fresh longan by acting on the antioxidant system and the metabolisms of membrane lipids and cell wall polysaccharides

Compared to the control longan, DNP treatment elevated pulp breakdown index, reduced the values of pulp firmness, CSP, ISP, cellulose, and hemicellulose by enhancing the activities of PE, PG, Cx, XET, and β-Gal. Additionally, DNP treatment increased the levels of PLD, lipase, LOX, PA, and SFA, and decreased the values of PC, PI, USFA, U/S, and IUFA, displaying higher cell membrane permeability and more severe cell membrane damage in longan pulp. Furthermore, DNP treatment weakened the levels of SOD, CAT, APX, AsA, GSH, TP, and TF, thereby exacerbating ROS outbreak and MDA production. These results indicate that DNP treatment destroyed the antioxidant system to cause ROS eruption. This disruption further disturbed the metabolisms of membrane lipids and cell wall polysaccharides, leading to the breakdown of cell membrane and cell wall, and eventually aggravated longan pulp softening and breakdown. However, ATP treatment exhibited the opposite effects of DNP treatment.

Preserving refrigeration and shelf life quality of hardy kiwifruit (Actinidia arguta) with alginate oligosaccharides preharvest application

Alginate oligosaccharide (AOS) is a bioactive carbohydrate known for its preservation properties. However, the efficacy of preharvest AOS treatment in maintaining the postharvest quality of hardy kiwifruit (Actinidia arguta) has not been previously reported. This study explores the effects of preharvest AOS treatment (80 mg L-1) on A. arguta fruit, assessing visual quality, physiological attributes, aroma, and antioxidant capacity during refrigeration and shelf life. Results showed that AOS treatment maintained higher lightness, chroma, firmness, and antioxidant levels (total phenolics, flavonoids, ascorbic acid, and glutathione), along with antioxidant enzyme activities (peroxidase, catalase, and ascorbate peroxidase). Specifically, AOS-treated fruit had 9% higher chroma and double the firmness after 60 days of refrigeration. AOS treatment reduced ripening and senescence, with 25% lower soluble solids content, 22% lower respiration rate, 30% lower ethylene production, and 35% lower malondialdehyde content. Electronic nose analysis indicated that AOS treatment suppressed changes in fruit aroma and off-odor development, maintaining significantly higher quality during the shelf life period. These findings demonstrate the effectiveness of AOS as a sustainable method to extend shelf life and preserve the quality of A. arguta fruit, enhancing its market value and consumer appeal. PRACTICAL APPLICATION: The research on using alginate oligosaccharides (AOS) for preharvest treatment of hardy kiwifruit (Actinidia arguta) has practical applications in the food industry. By extending the shelf life and preserving the quality of the fruit during storage, this method can help reduce postharvest losses and improve the market value and consumer appeal of A. arguta fruit. This sustainable preservation technique offers an eco-friendly alternative to traditional methods, enhancing the freshness and nutritional quality of the fruit available to consumers.

Salicylic Acid Treatment Ameliorates Postharvest Quality Deterioration in 'France' Prune (Prunus domestica L. 'Ximei') Fruit by Modulating the Antioxidant System

The potential of salicylic acid (SA) in delaying postharvest fruit senescence has been extensively documented; nevertheless, its effect on antioxidant activity and quality of 'France' prune fruit is largely unknown. The study investigated the effects of SA (0.5 mM) on postharvest quality deterioration of 'France' prune fruit. Results indicated that SA impeded the increase in respiration rate and weight loss, and mitigated the decrease of soluble solids content (SSC), titratable acidity (TA) content, firmness, and hue angle. SA sustained the ascorbate-glutathione cycle by inducing the production of ascorbic acid (AsA) and glutathione (GSH) and attenuates flavonoids, total phenols, and anthocyanins degradation by inhibiting polyphenol oxidase (PPO) activity and PdPPO. Moreover, SA significantly improved superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD), and glutathione reductase (GR) activities and gene expression levels, sustained higher 2,2'-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) and 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical scavenging capacity, ferric reducing antioxidant power (FRAP), and hydroxyl radical (·OH) inhibition capacity, and impeded the production of hydrogen peroxide (H2O2) and superoxide anion (O2•-). Overall, SA improved the antioxidant capacity by inducing the synthesis of defense response-related substances and promoting antioxidant enzyme activities to sustain the storage quality of 'France' prune fruit.

Metal-organic frameworks-based moisture responsive essential oil hydrogel beads for fresh-cut pineapple preservation

The preservation of fresh-cut fruits and vegetables has attracted attention to the shelf-life reduction caused by high humidity. Herein, alginate/copper ions cross-linking, in-situ growth and self-assembly techniques of metal-organic frameworks (MOFs) were utilized to prepare a moisture responsive hydrogel bead (HKUST-1@ALG). As the multistage porous structure formation, tea tree essential oil (TTO) load capacity in hydrogel bead (TTO-HKUST-1@ALG) was increased from 6.1% to 21.6%. TTO-HKUST-1@ALG had excellent moisture response performance, and the release rates of TTO increased from 33.89% to 70.98% with moisture increasing from 45% to 95%. Besides, TTO-HKUST-1@ALG exhibited excellent antimicrobial, antioxidant capacity, and biocompatibility. During storage, TTO-HKUST-1@ALG effectively improved the cell membrane integrity by maintaining the balance of reactive oxygen species metabolism. The degradation of cell wall structure and tissue softening were delayed by inhibiting the cell wall-degrading enzymes activity. Briefly, TTO-HKUST-1@ALG improved the storage quality and extended shelf-life of fresh-cut pineapple, which was a promising preservative.

Involvement of energy and cell wall metabolisms in chilling tolerance improved by hydrogen sulfide in cold-stored tomato fruits

KEY MESSAGE

Hydrogen sulfide improved cold resistance of tomato fruits by regulating energy metabolism and delaying cell wall degradation, thereby alleviating the damage of cold storage on fruits. Postharvest cold storage in tomato fruits extended shelf life but caused the appearance of chilling injury (CI), appeared by softness and spots on the surface of the fruits. These changes were linked closely with energy and cell wall metabolisms. Hydrogen sulfide (H2S), as the gaseous fresh-keeping regulator, was used in the present study to investigate the effects of H2S on energy and cell wall metabolisms in tomato fruits during cold storage. Fruits after harvest were fumigated with different concentrations (0, 0.5, 1, 1.5 mM) of sodium hydrosulfide (NaHS) solution as H2S honor for 24 h and stored at 4 °C for 25 days. The results showed that 1 and 1.5 mM NaHS solution fumigation promoted the accumulation of endogenous H2S, followed by the increase in L-cysteine desulfurase (LCD) and D-cysteine desulfurase (DCD) activities in fruits during cold storage. It was also found that 1 and 1.5 mM NaHS treatments improved H+-ATPase, Ca2+-ATPase, cytochrome C oxidase (CCO), and succinic dehydrogenase (SDH) activities. Moreover, the contents of cellulose and hemicellulose were increased by 1 and 1.5 mM NaHS, following down-regulated activities of cellulase (CL), pectin lyase (PL), α-mannosidase (α-man) and β-Galactosidase (β-Gal) and down-regulated expression of PL1, PL8, MAN4 and MAN7 genes. Thus, H2S alleviates CI led by cold storage in tomato fruits via regulating energy and cell wall metabolisms.

Construction of photocatalytic coating for alleviating the shriveling of postharvest fruit cucumber after simulated transportation

The shriveling of fruit cucumber was commonly occurred during supply chain, photocatalyst exposed to UV light can endow the coatings with ethylene removal capacity to reduce the respiration of fruit and water loss. The study developed a novel photodynamic technology responsive photocatalytic coating with exceptional ultraviolet (UV) photocatalytic degradation of ethylene ability to decay the shriveling of postharvest fruit cucumber during supply chain. This coating involved the integration of Carbon dots (CDs)-loaded nano ZnO and the skillful selection of pullulan (Pul) and apple pectin (AP) matrix. The CDs/ZnO coatings boasted an impressive array of photocatalytic degradation of ethylene and adhesion properties, including high ethylene removal rates of 32.04 % in 60 min UV light stimulation. The decrease of cell-wall strength, degradation of the cell wall polysaccharides and water loss resulted in cucumber shriveling. Compared with CK sample, after UV-CDs/ZnO coating treatment, the higher firmness and cell wall polysaccharides were found in cucumbers with lower cell wall degrading enzymes activities, weight loss and water movement, which was associated with the decrease of respiration and ethylene accumulation. The UV-CDs/ZnO coatings possessed promising potential for alleviating the shriveling of postharvest fruit cucumber and applications in fruits preservation in the future.

Characterization and the mechanism underlying the cryoprotective activity of a peptide from large yellow croaker (Pseudosciaena crocea)

Ice crystal-induced protein denaturation is the main cause of the deterioration of fish during frozen storage and transportation. In this study, the ultra-performance liquid chromatography - quadrupole - time of flight (UPLC-Q-TOF) technique was used to identify and screen tryptic peptides Ile-Glu-Glu-Leu-Glu-Glu-Leu-Glu-Ala-Glu-Arg (IEELEEELEAER) from large yellow croaker (Pseudosciaena crocea). The results were used study their cryoprotective effects on turbot fish meat during freeze-thaw cycles at different concentrations, and to investigate their anti-freezing mechanism. The results showed that the I-2.0 group effectively inhibiting the degeneration and structure changes of myofibrillar proteins after three freeze-thaw cycles, and the Ca2+-ATPase activity (1.65 μmolPi/mg/h), increased by 55.86% compared with that of the control group. Additionally, peptide IEELEEELEAER could provide antifreeze protection by binding to the surface of ice crystals and inhibiting their transformation. This peptide acts as a natural cryoprotectant and might be used for the cryogenic storage and transportation of fish products.

Synergistic Effects of 1-MCP Fumigation and ε-Poly-L-Lysine Treatments on Delaying Softening and Enhancing Disease Resistance of Flat Peach Fruit

Flat peach, a predominant fruit consumed in China, is highly susceptible to softening and perishable. The impact of 1-methylcycloproene (1-MCP) fumigation combined with ε-poly-L-lysine (ε-PL) on softening and postharvest reactive oxygen species (ROS) and phenylpropanoid pathway metabolisms in peaches and its relationship to disease resistance were investigated. Findings revealed that a combination of 1 µL L-1 1-MCP and 300 mg L-1 ε-PL effectively suppressed the activity of cell-wall-degrading enzymes and the disassembly of cell wall structure, thus maintaining higher firmness and lower decay incidence. Compared to the control group, the synergistic approach bolstered enzymatic responses linked to disease resistance and ROS-scavenge system, consistently preserving total phenolics, flavonoids, ascorbic acid, and glutathione levels. Concurrently, the accumulation of hydrogen peroxide and malondialdehyde was significantly diminished post-treatment. These results show that there is good synergistic effect between 1-MCP and ε-PL, which could effectively maintain the quality of flat peach fruit by modulating cell wall metabolism and enhancing the resistance.

Comprehensive Evaluation of Ten Actinidia arguta Wines Based on Color, Organic Acids, Volatile Compounds, and Quantitative Descriptive Analysis

Actinidia arguta wine is a low-alcoholic beverage brewed from A. arguta with a unique flavor and sweet taste. In this study, the basic physicochemical indicators, color, organic acid, and volatile aroma components of wines made from the A. arguta varieties 'Kuilv', 'Fenglv', 'Jialv', 'Wanlv', 'Xinlv', 'Pinglv', 'Lvbao', 'Cuiyu', 'Tianxinbao', and 'Longcheng No.2' were determined, and a sensory evaluation was performed. The findings show that 'Tianxinbao' produced the driest extract (49.59 g/L), 'Kuilv' produced the most Vitamin C (913.46 mg/L) and total phenols (816.10 mg/L), 'Jialv' produced the most total flavonoids (477.12 mg/L), and 'Cuiyu' produced the most tannins (4.63 g/L). We analyzed the color of the A. arguta wines based on CIEL*a*b* parameters and found that the 'Kuilv' and 'Longcheng No.2' wines had the largest L* value (31.65), the 'Pinglv' wines had the greatest a* value (2.88), and the 'Kuilv' wines had the largest b* value (5.08) and C*ab value (5.66) of the ten samples. A total of eight organic acids were tested in ten samples via high-performance liquid chromatography (HPLC), and we found that there were marked differences in the organic acid contents in different samples (p < 0.05). The main organic acids were citric acid, quinic acid, and malic acid. The aroma description of a wine is one of the keys to its quality. A total of 51 volatile compounds were identified and characterized in ten samples with headspace gas chromatography-ion mobility spectrometry, including 24 esters, 12 alcohols, 9 aldehydes, 3 aldehydes, 2 terpenes, and 1 acid, with the highest total volatile compound content in 'Fenglv'. There were no significant differences in the types of volatile compounds, but there were significant differences in the contents (p < 0.05). An orthogonal partial least squares discriminant analysis (OPLS-DA) based on the odor activity value (OAV) showed that ethyl butanoate, ethyl pentanoate, ethyl crotonate, ethyl isobutyrate, butyl butanoate, 2-methylbutanal, ethyl isovalerate, and ethyl hexanoate were the main odorant markers responsible for flavor differences between all the A. arguta wines. Sensory evaluation is the most subjective and effective way for consumers to judge A. arguta wine quality. A quantitative descriptive analysis (QDA) of the aroma profiles of ten grapes revealed that the 'fruity' and 'floral' descriptors are the main and most essential parts of the overall flavor of A. arguta wines. 'Tianxinbao' had the highest total aroma score. The flavor and quality of A. arguta wines greatly depend on the type and quality of the A. arguta raw material. Therefore, high-quality raw materials can improve the quality of A. arguta wines. The results of the study provide a theoretical basis for improving the quality of A. arguta wines and demonstrate the application prospects of HS-GC-IMS in detecting A. arguta wine flavors.