Hexane Treatment Research Articles

Normal-hexane treatment on PET-based waste fiber depolymerization process

Abstract The global increase in polyethylene terephthalate (PET)-based waste fiber poses a persistent environmental risk. While efforts have been made to repurpose waste fibers into bags, clothing, and building materials, the depolymerization process to extract pure raw materials for recycling remains underdeveloped. This study investigates the impact of normal hexane treatment on the purity of terephthalic acid (TPA) recovered from wastewater containing sodium terephthalate, ethylene glycol, and impurities generated during polyester fabric weight reduction or waste fiber recycling processes. Nuclear magnetic resonance analysis of the recovered TPA (rTPA) revealed a maximum purity of 99.81%, suggesting the effective removal of diverse contaminants such as adhesives and surfactants present in waste fibers through normal hexane and activated carbon treatments. This research contributes to the development of efficient and sustainable PET waste fiber recycling processes, highlighting the potential of normal hexane treatment in enhancing the purity of rTPA.

Hexane defatting effects on rapeseed protein extractability and properties at neutral and mild pH 8.5

Rapeseed is a promising plant protein source yet to be fully explored. Traditionally, rapeseed proteins are extracted from hexane-defatted press cake at high alkaline conditions to maximise protein recovery. Instead of the traditional approach, this study explored the effects of extracting proteins from the whole-kernel seed, focusing on assessing the hexane defatting process followed by gentle protein extraction at neutral pH compared with pH 8.5. Extraction at neutral pH resulted in a napin-rich protein extract, while alkaline conditions favoured cruciferin extraction as expected. Hexane defatting destroyed the oil bodies's structure while detaching the cell membrane from the cell wall, causing dehydration, and enabling interactions between the seed constituents. Increasing cycles of hexane treatment greatly reduced the total protein recovery by 9 g/100 g under neutral pH and >60 g/100 g under mild alkaline conditions which affected the protein structure, leading to a more rigid structure with a slightly higher melting temperature.

Improving blueberry cold storage quality: the effect of preharvest hexanal application on chilling injuries and antioxidant defense mechanisms.

Blueberries are vulnerable to chilling injury (CI). This can lead to limited longevity when they are subjected to cold storage conditions. This study investigated the effectiveness of a preharvest spray containing 0.02% hexanal in reducing CI and improving the postharvest storage quality of 'Star' and 'Biloxi' blueberries. The blueberries were stored for a period of 5 weeks at 2 °C and in 90% relative humidity (RH). The findings revealed that the preharvest hexanal spraying of both cultivars delayed senescence by mitigating CI, as evidenced by the bolstering of the antioxidant defense system through increased superoxide dismutase (SOD), ascorbate peroxidase (APX), peroxidase (POD), catalase (CAT), and phenylalanine ammonia lyase (PAL) enzyme activity. The treated fruit also maintained elevated levels of total phenol content (TPC), total flavonoids (TFC), and vitamin C, demonstrating enhanced free radical scavenging capacity (FRSC), while exhibiting reduced polyphenoloxidase (PPO) activity, and reduced malondialdehyde (MDA), and H2O2 content in comparison with the control group. The preharvest hexanal treatment also suppressed fruit softening by maintaining greater firmness and higher membrane stability index (MSI) scores, inhibiting the activity of polygalacturonase (PG), pectinmethylesterase (PME), xylanase, and α-amylase, and reducing microbial counts (MC) and incidence of decay (DI) in comparison with the control. Preharvest hexanal treatment also improved the overall storage quality by reducing weight loss, total soluble solids (TSS), pH, and the TSS/acid ratio, while increasing titratable acidity (TA) in comparison with the control during cold storage. The findings suggest that hexanal, as a preharvest application, delays senescence effectively and preserves overall quality by enhancing cold tolerance through antioxidant defense mechanisms in blueberry storage under cold conditions. © 2024 The Author(s). Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

In Vivo Oxidation and Wear in Remelted Highly Cross-Linked Polyethylene Liners Retrieved at a Minimum of 10 Years After Total Hip Arthroplasty

BackgroundWith the decreasing age threshold for patients undergoing total hip arthroplasty (THA), there is an escalating demand for enhanced polyethylene durability. Although reports assessing wear in remelted highly cross-linked polyethylene (HXLPE) through radiographic imaging exist, a consensus regarding its oxidation level is lacking. This study investigated the wear, oxidation levels, and degradation of remelted HXLPE that was retrieved at least 10 years after THA. MethodsOur analysis focused on 7 cases of melted HXLPE liners retrieved ≥10 years after THA. All patients were women, who had an average age of 64 ± 6.5 years at the initial operation, and the mean postoperative period after THA was 12 years and 11 months ±1 year and 5 months. The wear conditions were measured by matching the shape analysis data obtained from a coordinate-measuring machine with a spherical model. Fourier-transform infrared spectroscopy was used to study the oxidation of polyethylene, and the polyethylene structure was evaluated using scanning electron microscopy. ResultsOsteolysis was not observed in any case on X-rays, computed tomography, or intraoperative findings during revision surgery. The average oxidation index (OI) of the sliding surface under load was 0.31 ± 0.22 in the 6 cases calculated after hexane treatment, and 0.69 for one case without hexane treatment. In the 6 cases calculated after hexane treatment, the average OI of the non–load-bearing sliding surface was 0.11 ± 0.20. Average wear values were 0.33 ± 0.11 mm at 45 degrees from the equatorial direction and 0.04 ± 0.07 mm in the opposite direction. The initial structure of the polyethylene was preserved at all sites with low oxidation levels; however, in one case with stem subsidence, morphological changes and a high OI were observed. ConclusionsLong-term oxidation and wear of remelted HXLPE liners retrieved from THA patients were minimal.

Hexanal Treatment for Improving the Shelf-life and Quality of Fruits: A Review

Fruits are rich sources of bioactive compounds such as lycopene, tannins, β-carotene, resveratrol, and lignan. These bioactive compounds’ antioxidative, antimicrobial, and antidiabetic properties are important in the human diet. Since fruits are one of the major sources of health-promoting nutrients for human consumption, they have high economic value. Ripening is a developmental process which involves changes in the colour, texture, taste, and metabolite composition of fruits, thus affecting their quality. In the market, the good quality of fruits depends on the ripening stage. Rapid ripening could shorten the shelf-life and quality of fruits. Shortened shelf-life causes fruit spoilage during post-harvest, transport, storage, and distribution. In turn, it will cause economic losses in the fruit market. Low-temperature storage is one of the techniques to prolong the shelf-life of fruits. However, this technique requires an expensive facility to achieve and maintain the low temperature. On the other hand, it has been reported that hexanal treatment could prolong the shelf-life and quality of fruits. It is also cheaper and easier to apply. However, the ripening inhibition mechanism of hexanal is not yet fully understood. The effectiveness of hexanal treatment on different fruits is also unclear. Numerous publications on hexanal treatment reported different formulations, techniques, and effectiveness rates on different fruits. Optimised formulation and technique are important to develop an efficient hexanal treatment strategy. Therefore, the mechanism, effectiveness, formulation, technique, and development of hexanal-based products to prolong the shelf-life of fruits are discussed in this review.

Identification and characterization of organic and glycosidic acids in the crude resin glycoside fraction of Ipomoea lacunosa seeds

Resin glycosides are commonly found in plants belonging to the Convolvulaceae family. Ipomoea lacunosa L. (Convolvulaceae) is an herbaceous vine native to the United States. The resin glycosides of this plant have not been studied in detail. In this study, the components of the crude resin glycoside fraction extracted from the seeds of I. lacunosa are characterized. Alkaline hydrolysis of the crude resin glycoside fraction obtained from methanolic extract of the seeds yielded three organic acids, namely, 2S-methylbutyric, (E)-2-methylbut-2-enoic, and 2R-methyl-3R-hydroxybutyric acids, and a glycosidic acid fraction. Acidic hydrolysis of the glycosidic acid fraction yielded hydroxyl fatty acid components, including 7S-hydroxydecanoic, 11S-hydroxytetradecanoic, 11S-hydroxyhexadecanoic, 3S,11S-dihydroxytetradecanoic, 3S,11S-dihydroxyhexadecanoic, and 3S,12S-dihydroxyhexadecanoic acids, as well as monosaccharide components, including d-glucose, d-quinovose, d-fucose, and l-rhamnose. Trimethylsilyldiazomethane–hexane treatment of the glycosidic acid fraction further yielded eleven previously undescribed glycosidic acid methyl esters and two known glycosidic acid methyl esters. The structures of the obtained compounds were characterized using various spectral techniques. Four of the undescribed compounds were hexaglycosides, five were heptaglycosides, and two were octaglycosides. The aglycone of these compounds was either methyl 11S-hydroxytetradecanoate, methyl 3S,11S-dihydroxytetradecanoate, or methyl 3S,11S-dihydroxyhexadecanoate. Among the undescribed compounds identified, eight contained novel glycans, and three were rare bisdesmosides with sugar linkages at the C-3 and C-11 positions of methyl 3S,11S-dihydroxytetradecanoate.

Influence of Staggered Hexanal Treatment on Post-Storage Fruit Physiology, Functional Quality and Enzyme Activity of ‘Royal Delicious’ Apple

Influence of Staggered Hexanal Treatment on Post-Storage Fruit Physiology, Functional Quality and Enzyme Activity of ‘Royal Delicious’ Apple

Distinctive Processing Effects on Recovered Protein Isolates from Laurel (Bay) and Olive Leaves: A Comparative Study.

Although there is a well-known awareness of the nutritional potential of plant proteins, their utilization within food formulations is currently limited due to insufficient investigation of the functional properties or processing conditions. In this study, the protein contents of the remaining pulps of laurel (bay) (LL) and olive leaves (OL) after alcoholic washing (representing phenolic compound extraction), heat treatment (representing the usage of the leaves for tea brewing or as cooking aid), and deoiling process (representing oil extraction) were investigated. Bicinchoninic acid assay (BCA) indicated that the best protein yield was achieved with a direct isolation process after hexane oil removal. Both LL and OL isolates contained around 80% protein, but high temperature and alcohol content broke down the protein structure as well as decreased the final protein content (∼40%). Alcohol treatment appears to remove protein-bound phenols and increase fluorescence intensity in OL protein isolates while potentially causing structural alterations in LL proteins. In addition to a dramatic decrease in fluorescence intensity, the absolute zeta potentials of protein extracts of boiling OL and LL increased by 53 and 24%, respectively. The increased zeta potentials along with the decreased fluorescence intensity indicate the changes in the protein conformation and enhanced hydrophilicity of the protein structure, which can influence the functional properties of proteins. Protein extracts of deoiled LL had the highest ΔH value (180 mJ/mg), which is higher than other laurel and all olive protein samples. Laurel protein isolates became more thermally stable after hexane treatment. Moreover, the protein extracts after hexane treatment showed better emulsion capacity from both laurel (71.57%) and olive (61.87%). Water-binding capacity and thermal stability of the protein extracts from deoiled samples were higher than those of the other pretreatments, but the boiled samples showed higher oil-binding capacity due to protein denaturation. These findings indicate the importance of processing conditions in modulating protein properties for various applications.

Retaining overall quality of fresh figs by postharvest hexanal vapor treatment during cold storage

Figs (Ficus carica L.) are rich in nutrients, but their rapid metabolic changes due to the climacteric respiratory behavior during ripening make them a highly perishable commodity, which leads to quick deterioration in quality and a shortening storage period. In this study, the influence of hexanal vapor (0.01% or 0.02% introduced as HEX-I and HEX-II, respectively) treatments were evaluated on ‘Abbas’ figs during storage at 4 ± 1 °C, 90% RH for 18 d. Both concentrations of hexanal treatments delay senescence while retaining quality, as indicated by a greener fruit peel (lower a* value), higher pulp firmness, membrane stability index (MSI), titratable acidity (TA), and lower total soluble solids (TSS), weight loss, and TSS/acid ratio than the untreated fruit. Total content of phenol (TPC), flavonoid (TFC), and vitamin C, as well as free radical scavenging capacity (FRSC) were higher in hexanal-treated fruit as compared to untreated fruit. All hexanal-treated fruit had lower hydrolytic enzyme and polyphenoloxidase (PPO) activity but higher catalase (CAT) and peroxidase activity (POD) than the control. Decay incidence (DI) and microbial counts (MC) (mold and yeast) increased during storage but were suppressed in all treated fruit. Though both concentrations of hexanal were effective in retaining quality and delaying senescence, the higher concentration was more effective than the lower one. Therefore, hexanal vapor at 0.02% can be used to preserve quality and prolong the storage period of ‘Abbas’ figs under low-temperature storage conditions.

Hexane Treatment to Facilely Tailor Polyamide Nanofiltration Membrane Performance: The Critical Role of Treatment Duration

Hexane Treatment to Facilely Tailor Polyamide Nanofiltration Membrane Performance: The Critical Role of Treatment Duration

Identification of Cell-Attachment Factors Derived from Green Algal Cells Disrupted by Sonication in Fabrication of Cell Plastics.

Cell plastics which are composed of unicellular green algal cells have been proposed in previous studies. While unicellular green algae can be freely arranged using fabrication processes, a matrix is required to attach the cells together. To date, although the cell contents collected from Chlamydomonas reinhardtii show the possibility of attaching cells, but it is unclear which components can be considered attachment factors. Therefore, in this study, C. reinhardtii cells were disrupted with sonication, and the components were separated and purified with hexane. The cell plastics with only 0.5 wt% of intermediate showed similar mechanical properties to those with 17 wt% and 25 wt% of cell components that were untreated with hexane, meaning that the purified intermediates could function as matrices. The purified intermediate was composed of approximately 60 wt% of protein as the main component, and proteomic analysis was performed to survey the main proteins that remained after hexane treatment. The protein compositions of the cell content and purified intermediate were compared via proteomic analysis, revealing that the existing ratios of 532 proteins were increased in the purified intermediate rather than in the cell content. In particular, the outer structure of each of the 49 proteins-the intensity of which was increased by over 10 times-had characteristically random coil conformations, containing ratios of proline and alanine. The information could suggest a matrix of cell plastics, inspiring the possibility to endow the cell plastics with more properties and functions.

TMT-Based Quantitative Proteomics and Non-targeted Metabolomic Analyses Reveal the Antibacterial Mechanism of Hexanal against Vibrio parahaemolyticus.

Hexanal is a phytochemical with antimicrobial activity. However, its antibacterial effect and mechanism against Vibrio parahaemolyticus (V. parahaemolyticus) remain unclear. The study aims to elucidate the associated mechanism using tandem mass tag quantitative proteomics and non-targeted metabolomics. Hexanal treatment reduced intracellular ATP concentration, increased membrane permeability, and destroyed the morphology and ultrastructure of V. parahaemolyticus cells. Proteomics and metabolomics data indicated that 572 differentially expressed proteins (DEPs) and 241 differential metabolites (DMs) were identified in hexanal-treated V. parahaemolyticus. These DEPs and DMs were involved in multiple biological pathways including amino acid metabolism, purine and pyrimidine biosynthesis, etc. Bioinformatics analysis revealed that hexanal damaged the structure and function of cell membranes, inhibited nucleotide metabolism, and disturbed carbohydrate metabolism and tricarboxylic acid cycle (TCA) cycle, which ultimately resulted in growth inhibition and bacterial death. The study is conducive to better understand the mode of action of hexanal against V. parahaemolyticus and offers experimental foundation for the application of hexanal as the antibacterial agent in the seafood-associated industry.

Postharvest hexanal application delays senescence and maintains quality in persimmon fruit during low temperature storage.

Persimmon (Diospyros kaki L.) fruit is characterized by rapid metabolic changes following ripening, and softening occurs due to the gradual breakdown of the cell membrane by the direct catabolic cascades of the phospholipase-D enzyme on the phospholipid bilayer. The cell membrane weakening is also enhanced by the generation of ROS during stress conditions such as cold storage and postharvest handling. This research evaluated the postharvest hexanal dipping application on persimmon fruit storage quality. The response of "MKÜ Harbiye" persimmon fruit to exogenous hexanal at different concentrations (0.04% and 0.08%, named as HEX-I and HEX-II, respectively) on quality parameters, chilling injury (CI), microbial growth, antioxidant compounds, and free radical scavenging capacity (FRSC) during storage at 0 °C and 80-90± 5% RH for 120 d were evaluated. Both hexanal treatments retained quality and delayed senescence, as indicated by greener peel (lower a* and L* values), higher firmness, total phenol concentration (TPC), FRSC, and titratable acidity (TA), but lower weight loss, electrical conductivity (EC), rate of CO2 , ethylene production, decay, and microbial growth than the control. Total soluble solids (TSS) were lower in treated fruit than the control up to 100 days, but it was much lower in HEX-I treatment as compared to HEX-II treatment. HEX-I treatment exhibited lower CI than the other treatments during storage. Hexanal at 0.04% could be used to increase the storage period of "MKÜ Harbiye" persimmons up to 120 d at 0 °C and 80-90± 5% RH by retaining quality and delaying senescence. This article is protected by copyright. All rights reserved.

Effects of Phospholipase D Inhibitors Treatment on Membrane Lipid Metabolism of Postharvest Banana Fruit in Response to Mechanical Wounding Stress

Banana fruit is a widely cultivated and economically important crop, and it is susceptible to mechanical damage. The effects of three different phospholipase D inhibitors (0.1% n-butanol, 0.05% 2-butanol, and 0.1% hexanal) on the cell membrane integrity and membrane lipid metabolism in wounding banana fruits during storage were investigated. The results indicated that wounded banana treated with phospholipase D inhibitors showed significant (p < 0.05) delay in the ripening and senescence process than the control group after a 9-day storage. Of the three PLD inhibitors, hexanal showed the best effect in maintaining firmness, suppressing the increase of total soluble solids (TSS) and respiration rate, and reducing malondialdehyde (MDA) content and cell membrane permeability of wounded banana fruits. Furthermore, hexanal more efficiently decreased the phospholipase D (PLD) and lipoxygenase (LOX) activities, lowered the contents of phosphatidic acid (PA) and diacylglycerol (DAG), and inhibited the reduction of phosphatidylcholine (PC) and phosphatidylinositol (PI) after 6 days of storage, compared to n-butanol or 2-butanol. These results demonstrate that application of hexanal treatment may be a reliable method to delay the senescence of harvested bananas subjected to mechanical wounding.

Efficacy of Hexanal Field Spray on the Postharvest Life and Quality of Papaya Fruit (Carica papaya L.) in Kenya

Papaya is a thin-skinned fruit that ripens and softens over a very short time, usually in 3 days, predisposing the fruit to physical damage and phyto-pathogen invasion even with careful handling further shortening postharvest shelf life. The objective of this study was to determine the efficacy of Hexanal, naturally occurring compound, on-farm spray, in managing the postharvest shelf life of papaya in two agro-ecological zones in Kenya. A formulation of Hexanal containing Tween 20 and ethanol was made by volume basis (v/v) and spray treatment at 1 and 2% in “Solo sunrise” and “Mountain” papaya cultivars. The experiment was a randomized block design with ninety-six plants per farm randomly selected. Spraying was applied at 30 days, 30 + 15 days, and 15 days to harvest time on mature green papaya. Control papaya fruits were sprayed with clean tap water as control. Data were collected on color changes and fruit retention on tree. The fruits were harvested when two to three yellow stripes were visible from the lower end of the fruits for postharvest analysis. Hexanal sprayed papaya fruits were retained for at least 13 days longer compared to the control fruits on tree. Hexanal treatment at 2% revealed an improved effect on managing papaya postharvest shelf life. All fruits treated with Hexanal significantly showed reduced rate of color break, softening, and enhanced extension of fruit shelf life by at least 6 days. Hexanal treatment also delayed ethylene and respiratory peaks by three days and showed no significant ( P ≤ 0.05 ) difference in the levels of total titratable acidity and total soluble solids. The results of this study indicate that Hexanal applied as a preharvest spray on mature green “Solo sunrise” and “Mountain” papaya cultivars grown in Kenya, is effective in prolonging shelf life and postharvest quality.

Characterization and Expression of Phospholipase D Putatively Involved in Colletotrichummusae Disease Development of Postharvest Banana Fruit

Phospholipase D (PLD) in plants plays an important role in growth, development, and stress response. The effect of hexanal on PLD in banana fruit responding to Colletotrichum musae infection remains poorly understood. In this study, four putative PLD genes, named as MaPLD1, MaPLD2, MaPLD3, and MaPLD4 were identified from banana fruit. The four MaPLDs can be classified into three of the seven known PLD families according to sequence characterization. Their deduced amino acid sequences displayed homology of PLDs from other plant species. Furthermore, the specific expression analysis of PLD genes in banana fruit in response to infection in C. musae was studied and the response relationship between PLD family members and banana fruit under anthracnose stress was clarified. Changes in both the activity of PLD and PLC, and the connection between hexanal and phospholipases in the banana fruit C. musae infection were compared. The results showed that the incidence of disease in banana inoculated with C. musae was dramatically increased after 6 days of storage, the activation of PLD and PLC in infected anthracnose fruit before disease development, and that this activation was inhibited by hexanal treatment, which suggested that both enzymes play a protective role in banana fruit to cope with C. musae infection and the participation of hexanal in their regulation. Of the four MaPLD genes, the anthracnose had a stronger effect on MaPLD1 and MaPLD4. These data demonstrated that hexanal treatment could enhance fruit disease resistance to C. musae, and that PLD could take part in the disease defensive system of harvested banana fruit to C. musae by modulating the metabolism of cell membrane lipids, and thus suppress disease development in C. musae -inoculated banana during storage.

Hexanal application reduces postharvest losses of mango (Mangifera indica L. variety "Kent") over cold storage whilst maintaining fruit quality

Mango (Mangifera indica L.) is a widespread crop that is affected by many factors that promote deterioration and limit its shelf life. This study aims to evaluate the effect of hexanal treatment and cold storage conditions on mango quality and postharvest losses. Mangoes var "Kent" were harvested from a commercial orchard located in Korhogo in the northern area of Ivory Coast. The fruit was then dipped in an aqueous hexanal formulation and stored at a cold temperature (13 ºC) before ripening at laboratory temperature (30 °C). Their quality was assessed during storage and after ripening. The results showed that hexanal reduced postharvest losses by 22.85% and spoilage by 12% after four weeks of cold storage. Furthermore, the results revealed that hexanal treatment increased fruit firmness and ascorbic acid content compared to control fruit. However, there was no difference in soluble solids content, titratable acidity, pH, dry matter, and colour between treated and control fruit. Sensory analysis showed that hexanal treatment improved some sensory descriptors such as overall likeability, chewiness, sweetness, and colour of the mango flesh. Therefore, our study suggests that postharvest dipping of mangoes in the hexanal solution, combined with cold storage conditions, extends the shelf life of the fruit while maintaining or even improving its organoleptic features.

Volatile compositions of strawberry fruit during shelf life using pre and postharvest hexanal treatment

Changes in volatile compositions were determined in Rubygem strawberry variety related to pre and postharvest hexanal application during shelf life. For this concern, Rubygem variety was treated with hexanal vapor and spray applications which were, doses (0%, 0.01%, 0.02%) pre and postharvest after hexanal applications strawberry fruits were stored at 2°C and RH 90% conditions. Effects of hexanal spray and vapor applications of strawberry fruit volatile profiles were analyzed with HS-SPME/GC–MS techniques. Differences among treatments were identified in volatile compositions at 3 days intervals during 15 days of shelf life. The results showed that, hexanal application type and concentration effected the percentage of volatile composition of esters, ketones, terpens, alcohols, acids, aldehydes, and others during shelf life. The hexanal application form and concentration were effected the amount and composition of volatiles of Rubygem strawberry fruit. As a result, hexanal spray application has important effects on ester percentage, however, hexanal vapor treatment increased the alcohols percentage of strawberries at the end of shelf life. Practical applications Application of organic substances of hexanal pre and postharvest season has been successfully used due to their environmentally friendly effects. Hexanal is volatile gases, organic aldehydes which are the source of plant extract and used as food additives. There are many research on hexanal application to prevent microbial growth after harvest. In the present study, hexanal spray and vapor applications were used to determined the volatiles profile strawberries fruit during shelf life.

Hexanal induces early apoptosis of Aspergillus flavus conidia by disrupting mitochondrial function and expression of key genes.

Aspergillus flavus is a notorious saprophytic fungus that compromises the quantity and quality of postharvest grains and produces carcinogenic aflatoxins. The natural compound hexanal disrupts cell membrane synthesis and mitochondrial function and induces apoptosis in A. flavus; here, we investigated the molecular mechanisms underlying these effects. The minimum inhibition and fungicidal concentration (MIC and MFC) of hexanal against A. flavus spores were 3.2 and 9.6 μL/mL, respectively. Hexanal exposure resulted in abnormal spore morphology and early spore apoptosis. These changes were accompanied by increased reactive oxygen species production, reduced mitochondrial membrane potential, and DNA fragmentation. Transcriptomic analysis revealed that hexanal treatment greatly altered the metabolism of A. flavus spores, including membrane permeability, mitochondrial function, energy metabolism, DNA replication, oxidative stress, and autophagy. This study provides novel insights into the mechanism underlying the antifungal activity of hexanal, suggesting that hexanal can be used an anti-A. flavus agent for agricultural applications. KEY POINTS: • Hexanal exposure resulted in abnormal spore morphology. • The apoptotic characteristics of A. flavus were induced after hexanal treatment. • Hexanal could change the expression of key A. flavus growth-related genes.

Transcriptomics of Improved Fruit Retention by Hexanal in 'Honeycrisp' Reveals Hormonal Crosstalk and Reduced Cell Wall Degradation in the Fruit Abscission Zone.

Apples (Malus domestica Borkh) are prone to preharvest fruit drop, which is more pronounced in ‘Honeycrisp’. Hexanal is known to improve fruit retention in several economically important crops. The effects of hexanal on the fruit retention of ‘Honeycrisp’ apples were assessed using physiological, biochemical, and transcriptomic approaches. Fruit retention and fruit firmness were significantly improved by hexanal, while sugars and fresh weight did not show a significant change in response to hexanal treatment. At commercial maturity, abscisic acid and melatonin levels were significantly lower in the treated fruit abscission zone (FAZ) compared to control. At this stage, a total of 726 differentially expressed genes (DEGs) were identified between treated and control FAZ. Functional classification of the DEGs showed that hexanal downregulated ethylene biosynthesis genes, such as S-adenosylmethionine synthase (SAM2) and 1-aminocyclopropane-1-carboxylic acid oxidases (ACO3, ACO4, and ACO4-like), while it upregulated the receptor genes ETR2 and ERS1. Genes related to ABA biosynthesis (FDPS and CLE25) were also downregulated. On the contrary, key genes involved in gibberellic acid biosynthesis (GA20OX-like and KO) were upregulated. Further, hexanal downregulated the expression of genes related to cell wall degrading enzymes, such as polygalacturonase (PG1), glucanases (endo-β-1,4-glucanase), and expansins (EXPA1-like, EXPA6, EXPA8, EXPA10-like, EXPA16-like). Our findings reveal that hexanal reduced the sensitivity of FAZ cells to ethylene and ABA. Simultaneously, hexanal maintained the cell wall integrity of FAZ cells by regulating genes involved in cell wall modifications. Thus, delayed fruit abscission by hexanal is most likely achieved by minimizing ABA through an ethylene-dependent mechanism.