Presence of carbapenem resistance in hybrid E. coli pathovars from ready-to-eat fresh-cut fruits in Accra, Ghana.

AIM: This study reports the presence of carbapenem-resistant E. coli hybrid pathovars and its prevalence in 200 fresh-cut fruits from Accra. METHODS AND RESULTS: Standard culture methods were used to quantify microbial indicators and E. coli on fresh-cut fruits retailed in formal and informal outlets in Accra. The Kirby-Bauer disc diffusion method was used to determine the antibiotic resistance profile of E. coli, while multiplex PCR was employed to identify the virulence and carbapenem resistance genes. E. coli prevalence in cut-fruits was 17%, with pawpaw, watermelon, and mix-fruit having higher prevalence than pineapple. Of the 34 E. coli isolates from fresh-cut fruits, 44% showed broad resistance to beta-lactam antibiotics, while 5.9% showed carbapenem resistance. The study identified virulence genes associated with all E. coli isolates including stx1, stx2, escV, and ipaH, of which 97% were hybrid pathovars bearing genes for STEC/EPEC/EIEC. The carbapenemase gene, blaIMP, was associated with both carbapenem-resistant E. coli phenotypes identified. CONCLUSION: Despite a low carbapenem-resistance prevalence observed among E. coli isolates, hypervirulent hybrid strains of E. coli is present in fresh-cut fruits in the sampling area, posing a potential public health risk to fresh-cut fruit consumers.

Characterization of the extracellular proteases from Bacillus inaquosorum strain E1-8 and its application in the preparation of hydrolysates from plant and animal proteins with antioxidant, antifreeze and anti-browning properties.

BACKGROUND: Bacillus inaquosorum strains is widely recognized for their plant-growth-promoting and biocontrol capabilities, yet their roles in protease production remain unclear. The present study aimed to comprehensively assess the protease-producing performance of B. inaquosorum strain E1-8, at the same time as exploring the novel application of agricultural Bacillus proteases in the preparation of protein hydrolysates for fresh-cut fruits preservation. RESULTS: First, genomic sequencing revealed the diversity of E1-8 proteases, indicating 15 putative extracellular proteases. Subsequently, the fermentation conditions for E1-8 protease production were optimized, with sweet potato powder and soybean meal identified as the most suitable carbon and nitrogen sources, respectively, resulting in a maximum protease activity of 321.48 U mL-1. Upon culturing the strain under these optimized conditions, only an S8 family serine protease and an M48 family metalloprotease were revealed by secretomic analysis and protease inhibitor assays. Additionally, the optimal protease conditions for generating protein hydrolysates from soy, pea, fish and porcine proteins were determined. The molecular weight of the hydrolysates primarily ranged from 2000 to 180 Da, with a total of 17 amino acids identified. The application of these hydrolysates demonstrated a 2,2-diphenyl-1-picrylhydrazyl (i.e. DPPH) scavenging activity ranging from 58.64% to 84.12%, significantly reducing of the melting peaks and the freezing points. Furthermore, the browning index of apple slices stored at 4 °C decreased by 14.81% to 22.15% on the second day, and similar effects were observed in fresh-cut banana stored at 4 °C for 7 days. CONCLUSION: The protein hydrolysates obtained exhibit remarkable antioxidant, antifreeze and anti-browning properties for fresh-cut fruits. © 2024 Society of Chemical Industry.

Advanced application of slightly acidic electrolyzed water for fresh-cut fruits and vegetables preservation.

Fresh-cut fruits and vegetables (F&V) play a pivotal role in modern diets due to their convenience and nutritional value. However, their perishable nature renders them susceptible to rapid spoilage, causing quality deterioration, safety risks, and economic losses along the supply chain. Traditional preservation methods, while effective to some extent, often fall short in maintaining the quality and safety of fresh-cut F&V. This comprehensive review examines the utilization of slightly acidic electrolyzed water (SAEW) as a novel preservation technique for fresh-cut F&V. The review encompasses the production mechanisms, sterilization principles, classifications and application of SAEW. It explores the effects of SAEW on microbial inactivation, quality parameters, and metabolic pathways in fresh-cut F&V. Additionally, it assesses the synergistic effects of SAEW when combined with other preservation methods. SAEW demonstrates remarkable potential in extending the shelf life of fresh-cut F&V by effectively inhibiting microbial growth, suppressing browning, preserving chemical content, and influencing various metabolic processes. Moreover, its synergy with different treatments enhances its overall efficacy in maintaining fresh-cut F&V quality. The review highlights the promising role of SAEW as an innovative preservation approach for fresh-cut F&V. However, challenges regarding its widespread implementation and potential limitations require further exploration. Overall, SAEW stands as a significant contender in ensuring the safety and quality of fresh-cut F&V paving the way for future research and application in the food industry.

Mechanism of exogenous methyl jasmonate in regulating the quality of fresh-cut Chinese water chestnuts.

Fresh-cut Chinese water chestnuts (CWCs) are susceptible to yellowing and browning during storage due to mechanical damage and the loss of protective outer skin, adversely affecting their marketability and shelf life. Methyl jasmonate (MeJA) is currently extensively used for food preservation, but it has not been used in Chinese water chestnuts. This study investigated the effect of MeJA treatment on the quality of fresh-cut CWCs. Fresh-cut CWCs immersed in 20 µM MeJA solution for 10 min and stored at 10°C for 5 d effectively delayed the yellowing process, reduced the respiration rate, and minimized the weight and soluble solids loss during storage. In addition, MeJA treatment induced the activities of superoxide dismutase (SOD) and catalase (CAT), which improved the antioxidant capacity of fresh-cut CWCs and inhibited the generation of reactive oxygen species (ROS). Meanwhile, MeJA treatment inhibited the activities of phenylalanine aminotransferase (PAL), polyphenol oxidase (PPO) and peroxidase (POD). The results of quantitative real-time PCR (qRT-PCR) showed that MeJA down-regulated the expression of CwCHS1, CwCHS2, CwCHS3 and CwCHI2 in freshly cut CWCs and inhibited the accumulation of flavonoids, thus delaying the surface discoloration of freshly cut CWCs.

Effects of film-forming components on the viability of probiotics and the application of synbiotic pectin film in preserving Da Xanh pomelo and Thai jackfruit fresh-cut.

Minimally processed products are highly convenient, and fresh-cut fruits coated with the synbiotic film have many advantages. This study investigated the film-forming components and preservation ability of Da Xanh pomelo and Thai jackfruit fresh-cut by synbiotic pectin film. The results showed that PA70 film combined with 1.5% FOS (fructooligosaccharides) had the highest number of viable cells of L. plantarum after 30 days of storage at 5 °C. The number of probiotic cells existing on fresh-cut products of Da Xanh pomelo and Thai jackfruit was always high (> 8 log CFU/g) and stable during 10 days of storage. In addition, jackfruit and pomelo fresh-cut preserved with probiotic film also showed probiotic activity in simulated stomach and small intestine medium with the number of probiotic cells (> 6 log CFU/g) and survival cell ratio after 4 h in small intestine medium reached 81.20 ± 0.92% (pomelo) and 82.16 ± 0.94% (Thai jackfruit).

Microfluidic-blow-spinning of carvacrol-loaded porphyrin metal - organic framework nanofiber films with synergistic antibacterial capabilities for food packaging.

The adherence of foodborne microorganisms threatens human health, necessitating the development of antibacterial food packaging films. In this study, the antibacterial agent carvacrol (CV), hindered by its high volatility and intense aromatic odor, was encapsulated within the photosensitive metal-organic frameworks (MOFs) material PCN-224 (loading rate 50%). Subsequently, the microfluidic-blow-spinning (MBS) technique was employed for the rapid fabrication of CV@PCN-224/polycaprolactone (PCL)/chitosan (CS) nanofiber films. The incorporation of CV@PCN-224 NPs enhances the nanofiber films' thermal stability and mechanical properties and improves the water vapor permeability while maintaining the sustained release of CV over an extended period and good biocompatibility. Due to the simultaneous loading of antibacterial agent (CV) and photosensitive agent (PCN-224), the CV@PCN-224/PCL/CS films exhibited good synergistic antibacterial functionality, as demonstrated by effective inhibition against both E. coli and S. aureus. All results show the vast potential of the prepared nanofiber films in antibacterial food packaging.

Alginate coatings applied on apple cubes as a vehicle for Lacticaseibacillus casei: probiotic viability and overall quality of a new functional product.

BACKGROUND: Worldwide, vegan and vegetarian lifestyles, as well as food allergies and intolerance (e.g. lactose intolerance and milk protein allergy) demand the development of alternatives to dairy-based probiotic foods. In the present study, probiotic Lacticaseibacillus casei CECT 9104 was added to alginate-based edible coatings enriched with inulin and oligofructose and applied to fresh-cut apple. Microbiological, physicochemical and sensory quality parameters of the apple cubes were monitored during 8 days of refrigerated storage. Lacticaseibacillus casei was tested for its antagonistic effect against inoculated Listeria innocua and Escherichia coli O157:H7. The viability of the probiotic strain during refrigerated storage and after simulated gastrointestinal digestion (GID) was evaluated. RESULTS: After 8 days of storage, 9.52-9.64 log colony-forming units (CFU) g-1 of L. casei were detected in apple samples. The functional apple cubes retained 8.31-8.43 log CFU g-1 of the probiotic after GID, without a significant effect of prebiotic addition. The microbiological quality and nutritional properties were maintained by the use of active coatings, whereas the sensory quality decreased after 8 days of storage. A bactericidal effect was exerted by the probiotic strain loaded in the coating against L. innocua artificially inoculated on apple cubes. Escherichia coli O157:H7 counts were reduced by 2.5 log after 8 days. CONCLUSION: This study has demonstrated the suitability of apple cubes as an alternative matrix to milk for carrying probiotic L. casei CECT 9104 and prebiotics, offering a promising alternative for the development of plant-based functional foods. © 2024 Society of Chemical Industry.

Dual imaging technique for a real-time inspection system of foreign object detection in fresh-cut vegetables.

Fresh-cut vegetables are a food product susceptible to contamination by foreign materials (FMs). To detect a range of potential FMs in fresh-cut vegetables, a dual imaging technique (fluorescence and color imaging) with a simple and effective image processing algorithm in a user-friendly software interface was developed for a real-time inspection system. The inspection system consisted of feeding and sensing units, including two cameras positioned in parallel, illuminations (white LED and UV light), and a conveyor unit. A camera equipped with a long-pass filter was used to collect fluorescence images. Another camera collected color images of fresh-cut vegetables and FMs. The feeding unit fed FMs mixed with fresh-cut vegetables onto a conveyor belt. Two cameras synchronized programmatically in the software interface simultaneously collected fluorescence and color image samples based on the region of interest as they moved through the conveyor belt. Using simple image processing algorithms, FMs could be detected and depicted in two different image windows. The results demonstrated that the dual imaging technique can effectively detect potential FMs in two types of fresh-cut vegetables (cabbage and green onion), as indicated by the combined fluorescence and color imaging accuracy. The test results showed that the real-time inspection system could detect FMs measuring 0.5 mm in fresh-cut vegetables. The results showed that the combined detection accuracy of FMs in the cabbage (95.77%) sample was superior to that of green onion samples (87.89%). Therefore, the inspection system was more effective at detecting FMs in cabbage samples than in green onion samples.

Transcriptome Analysis of Ethylene-Related Genes in Chlorine Dioxide-Treated Fresh-Cut Cauliflower.

Chlorine dioxide (ClO2) is widely used for the quality preservation of postharvest horticultural plants. However, the molecular mechanism of how ClO2 works is not clear. The purpose of this study was to understand ethylene-related molecular signaling in ClO2-treated fresh-cut cauliflower florets. Transcriptome analysis was used to investigate ethylene-related gene regulation. A total of 182.83 Gb clean data were acquired, and the reads of each sample to the unique mapped position of the reference genome could reach more than 85.51%. A sum of 2875, 3500, 4582 and 1906 differential expressed genes (DEGs) were identified at 0 d, 4 d, 8 d and 16 d between the control group and ClO2-treated group, respectively. DEGs were enriched in functions such as 'response to oxygen-containing compounds' and 'phosphorylation', as well as MAPK signaling pathway, plant hormone transduction pathway and so on. Genes, including OXI1, MPK3, WRKY22 and ERF1, which are located at the junction of wounding, pathogen attack, pathogen infection or ethylene signal transduction pathways, were up-regulated in response to stress. ETR and CTR1 (both up-regulated), as well as three down-regulated genes, including BolC5t34953H (a probable NAC), BolC1t05767H (a probable NAC) and BolC2t06548H (a probable ERF13), might work as negative regulators for ethylene signal transduction. In conclusion, ethylene-related genes and pathways are involved in ClO2 treatment, which might enhance stress resistance and have a negative feedback mechanism.

α-Lipoic acid treatment regulates enzymatic browning and nutritional quality of fresh-cut pear fruit by affecting phenolic and carbohydrate metabolism.

Fresh-cut pear fruit is greatly impacted by enzymatic browning, and maintaining quality remains a challenge. This study examined the impact of exogenous α-lipoic acid (α-LA) treatment on enzymatic browning and nutritional quality of fresh-cut pears. Results revealed that 0.5 g/L α-LA treatment effectively maintained color and firmness, and inhibited the increase in microbial number. The α-LA treatment also reduced MDA and H2O2 contents, decreased PPO activity, and enhanced SOD, CAT, and PAL activities. The α-LA treatment notably upregulated phenolic metabolism-related gene expression, including PbPAL, Pb4CL, PbC4H, PbCHI and PbCHS, and then increasing total phenols and flavonoids contents. Furthermore, it also influenced carbohydrate metabolism-related gene expression, including PbSS, PbSPS, PbAI and PbNI, maintaining a high level of sucrose content. These findings indicated that α-LA treatment showed promise in reducing browning and enhancing fresh-cut pears quality, offering a potential postharvest method to prolong the lifespan and maintain nutritional quality.

Evaluation of acetic acid treatment of fresh-cut water chestnuts using gray-correlation analysis based on the variation-coefficient weight.

Introduction: The demand for fresh-cut water chestnuts, a convenient and nutritive vegetable, is increasing in market. However, the slicing of water chestnuts can cause mechanical damage to tissue, which results in quality deterioration. We aimed to select the optimal treatment through a comprehensive comparison of the preservation effect of acetic acid, which could prolong the shelf life of fresh-cut water chestnuts and improve their storage quality. Methods: A comprehensive evaluation was conducted using the gray-correlation method based on the variation-coefficient weight to observe the treatment of 0, 2 and 5% acetic acid. Their effects on color, weight loss rate, and the content of ascorbic acid, total sugar, reducing sugar, soluble protein, and free amino acid were determined. Results: The color, weight loss rate, and nutritional content of fresh-cut chestnuts varied under different processing and storage times. When stored for more than 4 days, the b* value, and the content of total sugar and soluble protein in CK were higher than those in 2% or 5% acetic acid, but the weight loss rate, and the content of ascorbic acid and free amino acid in CK were less than those in acetic acid treatments. Considering various indicators, it was difficult to determine which treatment to choose for fresh-cut water chestnut preservation. The gray-correlation analysis results indicated that when stored for 8, 12, or 16 days, the gray-correlation degree of 5% acetic acid was the highest, while that of the control was the lowest. It could be directly concluded by the gray-correlation degree that when the storage time exceeded 4 days, acetic acid could be used to improve storage quality, and 5% acetic acid had a better preservation effect than 2%. Fresh-cut water chestnuts can be stored for 4 days without the need for acetic acid treatment. Conclusion: These findings could provide information and comprehensive evaluation methods for the preservation of fresh-cut fruits and vegetables. The next step is to evaluate the preservation effect of acetic acid by measuring its effects on other indicators of fresh-cut water chestnuts (e.g., flavonoids, and microorganisms), providing ideas for the research of preservatives.

Transcriptome analysis reveals ozone treatment maintains ascorbic acid content in fresh-cut kiwifruit by regulating phytohormone signalling pathways.

Ascorbic acid (AsA) is an indicator of the nutritional value of freshly cut kiwifruit during storage at 4℃, and its degradation can be inhibited after ozone treatment (1 mg/L, 10 min). The aim of this study was to elucidate the regulatory mechanism affecting AsA metabolism in fresh-cut kiwifruit after ozone treatment. In this study, ozone treatment not only prevented the decrease in AsA/dehydroascorbic acid and delayed the accumulation of total soluble solids/titratable acidity, but also altered phytohormone levels differently. Transcriptomic profiling combined with cis-acting element and correlation analysis were performed to reveal that abscisic acid and salicylic acid synergistically delay AsA degradation under ozone-treatment conditions. Actinidia03760, encoding ascorbate peroxidase, could be specifically recognized by the bZIP transcription factor and is considered a key candidate gene for further research. Collectively, ozone treatment is a promising method for preserving AsA content and improving the nutrition of fresh-cut kiwifruit.

Active Packaging Film Developed by Incorporating Starch Aldehyde-Quercetin Conjugate into SPI Matrix.

In this study, soy protein isolate (SPI) films incorporating quercetin-grafted dialdehyde starch (DAS-QR) and DAS/QR, respectively, were developed. The structural, physical, and functional properties of the composite films were determined. The results suggested that DAS-QR and DAS/QR formed hydrogen bonding with the SPI matrix, which improved the structural properties of the films. The light-blocking capacity, thermal stability, hydrophobicity, tensile strength, elongation at break, and antioxidant and antibacterial abilities of SPI films were improved by DAS-QR and DAS/QR. Notably, SPI films incorporated with DAS-QR exhibited better performance than those with DAS/QR in terms of antioxidant (SPI/DAS-QR: 79.8% of DPPH and 62.1% of ABTS scavenging activity; SPI/DAS/QR: 71.4% of DPPH and 56.0% of ABTS scavenging activity) and antibacterial abilities against S. aureus (inhibition rate: 92.7% for SPI/DAS-QR, 83.4% for SPI/DAS/QR). The composite coating film SPI/DAS-QR effectively maintained appearance quality, delayed the loss of weight and total soluble solids, postponed malondialdehyde accumulation, and decreased peroxidase activity and microbial contamination in fresh-cut potatoes. These good performances highlight SPI/DAS-QR as a promising active packaging material for fresh-cut product preservation.

γ-aminobutyric acid treatment inhibits browning and promotes storage quality by regulating reactive oxygen species and membrane lipid metabolism in fresh-cut stem lettuce.

The effects of γ-aminobutyric (GABA) on enzymatic browning, storage quality, membrane and reactive oxygen species (ROS) metabolism in fresh-cut stem lettuce were investigated. The results illustrated that GABA treatment delayed browning degree, polyphenol oxidase (PPO) activity and the expression of LsPPO. Meanwhile, higher chlorophyll and ascorbic acid contents were exhibited in GABA-treated stem lettuce, as well as the slower microbial propagation. Further investigation revealed that exogenous GABA application declined malondialdehyde content, electrolyte leakage and the enzyme activities of membrane metabolism, and the expression levels of related genes were also downregulated. In addition, GABA treatment scavenged ROS and strengthened the enzyme activities of ROS metabolism, as well as the expression levels of corresponding genes. Taken together, these findings implied that the repressed enzymatic browning and microbial propagation in GABA-treated stem lettuce were due to the inhibition of ROS accumulation, enhancement of membrane stability and increased resistance to oxidation.

Combined Ascorbic Acid and Mild Heat Treatment to Improve the Quality of Fresh-Cut Carrots.

Mild heat (MH) treatment and ascorbic acid (AsA) addition can improve the quality of fresh-cut produce when used individually; however, their combined effect remains unclear. Herein, fresh-cut carrots were used as models to explore the effects of MH (50 °C)-AsA (0.5%) on quality properties including reactive oxygen species (ROS) metabolism, antioxidants, lignin metabolism, naturally present microbes, and inoculated pathogens (Escherichia coli O157: H7 and Salmonella Typhimurium) during storage (0-5 d, 4 °C). The results indicate that the antioxidant properties in the MH-AsA group were consistent with those of single treatments, resulting in a consistent ROS-scavenging effect. From day 3-5, lignin synthesis was significantly inhibited by MH-AsA as compared with single treatments, probably because the two enzymes (phenylalanine ammonia-lyase and peroxidase) responsible for lignin synthesis exhibited lower expressions. Microbial analysis revealed that MH-AsA treatment led to the lowest counts of both pathogens and aerobic mesophilic bacteria at 0-5 d. Conversely, the inhibitory effect of MH-AsA treatment on mold and yeast was consistent with the single treatments. These results suggest that MH-AsA is a low-cost and safe approach to improve the physiological characteristics of fresh-cut produce while reducing microbial risk.

Prediction model of browning inhibitor concentration and its optimal composition for mass processing of ready-to-eat fresh-cut 'Fuji' apple (Malus domestica Borkh.) strains.

In this study, we optimized the composition of the browning inhibitor for apples and established a prediction model for the browning inhibitor concentration in mass-processed fresh-cut apples based on electrical conductivity measurements. The "Fuji" apples that were harvested in Chungju, Korea, were used for this study. Vitamin C mixture (VCM) and trehalose (Tre) were used as browning inhibitors at a 4% ratio. The browning reaction under Δ3 of BI (browning index) for 5 days was defined as the target shelf-life of the apple flesh. The ΔBI of VCM and Tre was lower than that of VCM by 4%. It is revealed that the electrical conductivity of the browning inhibitor was highly correlated with its concentration and the number of soaked apples. Finally, the regression of the conductivity was fitted as Y = -0.0024 (number of soaked apples) + 0.5111 (R2 = 0.9931). In the validation test, the conductivity must be maintained at 0.4373 S/m or higher to maintain the target anti-browning level of Δ3 or less, which corresponded to ∼80% of the initial qualitative level after manufacture. The conductivity measurement of the browning inhibitor is suitable for monitoring and predicting its concentration in the mass processing of fresh-cut apple production due to the convenience of this method. PRACTICAL APPLICATION: The conductivity measurement of browning inhibitors can be applied not only to the mass processing of apple production but also to the anti-browning treatment of other fruits and vegetables, due to the convenience of this method. From these research results, it is expected to derive a formula that can predict the concentration of browning inhibitors through simple experiments for other fruits or vegetables.

An insect lac blanket-mimetic and degradable shellac hydrogel/chitosan packaging film with controllable gas permeation for fresh-cut vegetables preservation.

Fresh-cut products are extremely perishable due to the processing operations, and the atmosphere environment, especially CO2, O2 and H2O, could profoundly affect their shelf life. Herein, an insect "lac blanket"-mimetic and facile strategy was proposed for fresh-cut vegetables preservation, employing porous shellac hydrogel microparticles as gas "switches" in chitosan film to regulate CO2, O2 and H2O vapor permeability. Thus, the shellac hydrogel/chitosan hybrid film presented the controllable and wide range of gas permeability, compared with the chitosan film. The shellac-COOH nanoscale vesicles aggregated to form shellac hydrogel network via hydrophobic binding. The shellac hydrogel microparticles played a certain lubricating effect on the hybrid film casting solution. The hydrogen bond network between shellac hydrogel and chitosan contributed to the excellent mechanical properties of the hybrid film. The hybrid film also exhibited remarkable water-resistant, antifogging properties, optical transparency and degradability. The hybrid packaging films prepared through this strategy could adjust the internal gas (CO2, O2, H2O and ethylene) contents within the packages, and further exhibited admirable preservation performance on three fresh-cut vegetables with different respiratory metabolisms. This gas permeation-controlled strategy has great potential in fresh food preservation and various other applications that need a modified atmosphere.

Effects of washing with boric acid solutions on residual boric acid content, microbiological load, and quality of fresh-cut spinach.

Insufficient disinfection of fresh-cut spinach poses significant health risks, along with potential issues like odor, color changes, and softening during short-term storage. To address these challenges, boric acid solutions were explored as an alternative to chlorine washes, which are known to produce toxic compounds. Among various concentrations, 1 % boric acid exhibited the most effective microbial inactivation, leading to substantial reductions in total mesophilic aerobic bacteria, total yeast and mold, and Enterobacteriaceae counts, with reductions of 1.64, 1.38, and 1.77 logs, respectively. Additionally, washing spinach leaves with this solution for 1 min maintained quality parameters, with enhanced antioxidant activity (55.26 mg kg-1 Trolox equivalent), increased total phenolic content (1214.06 mg kg-1 gallic acid equivalent), retention of chlorophyll a (839.16 mg kg-1), chlorophyll b (539.61 mg kg-1) and ascorbic acid content (264.72 mg kg-1). Mechanical properties such as puncture strength (1.81 N) and puncture distance (52.78 mm) also showed favorable outcomes, alongside optimal moisture content at 89.81 %. Notably, residual boric acid content was lowest in spinach leaves (1252.49 mg kg-1) and highest in the wash water (53.88 mg kg-1) after treatment. Scanning electron microscopy images demonstrated maintained tissue integrity, while Hunter Lab readings indicated minimal color changes post-washing. Additionally, sensory evaluations and various physicochemical analyses further supported the efficacy of boric acid washing. Consequently, washing spinach leaves with a 1 % boric acid solution for 1 min yielded favorable results across multiple quality parameters. These findings suggest the potential of boric acid as a safe and effective alternative disinfectant in the fresh-cut produce industry, highlighting its practical implications for food safety and quality. Future research should focus on exploring long-term effects and optimizing washing protocols for broader applications.

Inhibitory effect and molecular mechanism on tyrosinase and browning of fresh-cut apple by longan shell tannins.

Tyrosinase is a biological macromolecule closely related to browning of fruit and vegetables, melanin production, and tyrosinase inhibitors are usually used to prevent browning and pigmentation. In this study, longan shell tannins (LSTs) were screened as tyrosinase inhibitors and their structures were proved to be mixtures of procyanidins (condensed tannins) and ellagitannins (hydrolyzed tannins). Enzymatic experiments verified that LSTs were efficient inhibitors, and the IC50 values for monophenolase and bisphenolase were 176.04 ± 10 and 59.94 ± 5 µg mL-1, respectively. Fluorescence detections and molecular docking revealed that the combination of LSTs to tyrosinase was mainly driven by hydrogen bonding, hydrophobic interaction, as well as van der Waals force, which changed the microenvironment of tyrosine and tryptophan residues as well as enzyme conformation. Circular dichroism and molecular dynamics simulation showed that LSTs affected secondary structures of tyrosinase, resulting in structural stretching and conformational modification of the enzyme. In addition, preservation studies demonstrated that LSTs owned the ability to delay the browning of fresh-cut apples by inhibiting phenolic metabolism, strengthening the antioxidant system, and reducing lipid peroxidation. This paper testified that LSTs are exteaordinary tyrosinase inhibitors, and offered a scientific foundation for the application of LSTs in food industry and medicine.

Preservative effects of Osmanthus fragrans flower flavonoids on fresh-cut Yuluxiang pear.

Osmanthus fragrans flower flavonoids (OFFF) possess superior antioxidant and antibacterial activities. However, scant information exists on the efficacy of these secondary metabolites as preservatives for fresh-cut fruits and vegetables. Here, OFFF were tested as a natural preservative for the first time in fresh-cut Yuluxiang pear (Pyrus bretschneideri Rehd.) to assess effects on fruit quality. OFFF-treated samples showed significant retention of firmness, titratable acid, soluble solid content, and weight. Moreover, OFFF maintained the original fruit color, inhibited the decline of total phenol, reducing power and 2,2-diphenyl-1-picrylhydrazyl radical scavenging power, and diminished polyphenol oxidase and peroxidase oxidase activities. Furthermore, OFFF treatment effectively inhibited microbial growth. OFFF-treated samples also displayed better sensory quality. Considering cost and effectiveness, the most suitable concentrations of OFFF extract for fresh-cut Yuluxiang pear preservation were 0.7 and 0.9 mg/mL. The results indicate that OFFF treatment may be a potent strategy to inhibit browning and enhance nutritional properties of fresh-cut pear fruit.