Tomato Surfaces Research Articles

Keratin-Based Composite Bioactive Films and Their Preservative Effects on Cherry Tomato.

In this study, keratins were extracted from pig nail waste through the reduction method using L-cysteine as a reductant. Curcumin was successively incorporated in a mixed solution including keratin, gelatin, and glycerin to prepare different kinds of keratin/gelatin/glycerin/curcumin composite films. The morphology of the keratin/ gelatin/glycerin/curcumin composite films were examined using scanning electron microscopy. The structures and the molecular interactions between curcumin, keratin, and pectin were examined using Fourier transform infrared spectroscopy and X-ray diffraction, and the thermal properties were determined through thermogravimetric analysis. The tensile strengths of keratin/gelatin/glycerin/curcumin and keratin/gelatin/curcumin composite films are 13.73 and 12.45 MPa, respectively, and their respective elongations at break are 56.7% and 4.6%. In addition, compared with the control group (no film wrapped on the surface of tomato), the ratio of weight loss of the keratin (7.0%)/gelatin (10%)/glycerin (2.0%)/curcumin (1.0%) experimental groups is 8.76 ± 0.2%, and the hardness value of the tomatoes wrapped with composite films is 11.2 ± 0.39 kg/cm3. Finally, the composite films have a superior antibacterial effect against Staphylococcus aureus and Escherichia coli because of the addition of curcumin. As the concentration of curcumin reaches 1.0%, the antibacterial activity effect of the film is significantly improved. The diameter of the inhibition zone of E. coli is (12.16 ± 0.53) mm, and that of S. aureus is (14.532 ± 0.97) mm. The multifunctional keratin/gelatin/glycerin/curcumin bioactive films have great potential application in the food packaging industry.

Effects of plasma bubble-activated water on the inactivation against foodborne pathogens on tomatoes and its wash water

The aims of the study were to evaluate the decontamination effect and inactivation mechanism of a plasma bubble-activated water (PBAW) treatment against foodborne pathogens and to analyze the physicochemical properties of PBAW. A decrease in pH and an increase in the oxidation-reduction potential of PBAW were observed. The study characterized the PBAW decontamination of Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes on tomato and its wash water. A 20-min PBAW treatment reduced foodborne pathogens on tomatoes and in wash water to levels below the detection limit (1 log CFU/g or 1 log CFU/mL, respectively). The PBAW treatment did not change the color properties of tomatoes. Propidium iodide uptake and membrane lipid peroxidation of PBAW-treated bacteria significantly increased with prolonged treatment time (P < 0.05). The hydrogen peroxide, nitrite, and nitrate concentrations in PBAW increased along with PBAW treatment time. These results indicated that PBAW effectively inactivated foodborne pathogens inoculated on tomato surfaces and in wash water by oxidizing the cell membrane and causing a loss of membrane integrity through the action of reactive species dissolved in the PBAW. This study demonstrates the potential for the application of the PBAW treatment to enhance the microbiological safety of the washing process with no deterioration in product quality.

The preharvest application of Aureobasidium pullulans S2 remodeled the microbiome of tomato surface and reduced postharvest disease incidence of tomato fruit

Microbial communities associated with plants are vital to regulating plant growth and controlling disease, although their potential functions have not been fully explained. The study of plant microbiome can help understand the microbial community structure. Thus, directional induction and remodeling microbial communities could reduce postharvest diseases and preserve fruit quality. This study employed high-throughput sequencing to determine whether the fungal and bacterial communities on tomato surface were changed due to preharvest treatment with Aureobasidium pullulans S2. At the same time, postharvest diseases, fruit quality, and surface microbial communities were examined during storage. The results showed that with the preharvest application of A. pullulans S2, significant changes were observed in fungal and bacterial communities of tomato during storage, including an increased fungal alpha diversity, shifts in community composition and structure (removed the abundance of Aureobasidium). Several potentially beneficial genera, Papiliotrema, Oidiodendron, Chloridium, Simplicillium, Methylobacterium and Acinetobacter, were found by analysis of the relationship between microbial taxa with fruit decay incidence and significantly enriched genera in the treatment group during storage. The functions of these taxa on tomatoes require further investigation, which will be helpful for directional regulation of the microbial composition in fruit and vegetables to achieve sustainable disease control strategies.

SARS-CoV-2 pseudotyped virus persists on the surface of multiple produce but can be inactivated with gaseous ozone

Due to the immense societal and economic impact that the COVID-19 pandemic has caused, limiting the spread of SARS-CoV-2 is one of the most important priorities at this time. The global interconnectedness of the food industry makes it one of the biggest concerns for SARS-CoV-2 outbreaks. Although fomites are currently considered a low-risk route of transmission for SARS-CoV-2, new variants of the virus can potentially alter the transmission dynamics. In this study, we compared the survival rate of pseudotyped SARS-CoV-2 on plastic with some commonly used food samples (i.e., apple, strawberry, grapes, tomato, cucumber, lettuce, parsley, Brazil nut, almond, cashew, and hazelnut). The porosity level and the chemical composition of different food products affect the virus's stability and infectivity. Our results showed that tomato, cucumber, and apple offer a higher survival rate for the pseudotyped viruses. Next, we explored the effectiveness of ozone in deactivating the SARS-CoV-2 pseudotyped virus on the surface of tomato, cucumber, and apple. We found that the virus was effectively inactivated after being exposed to 15 ppm of ozone for 1 h under ambient conditions. SEM imaging revealed that while ozone exposure altered the wax layer on the surface of produce, it did not seem to damage the cells and their biological structures. The results of our study indicate that ozonated air can likely provide a convenient method of effectively disinfecting bulk food shipments that may harbour the SARS-CoV-2 virus.

Attachment and Survival of Salmonella enterica and Listeria monocytogenes on Tomatoes (Solanum lycopersicum) as Affected by Relative Humidity, Temperature, and Storage Time

Tomatoes (Solanum lycopersicum) are one of the most commonly consumed fruits worldwide. The fruit can become contaminated with Salmonella and Listeria monocytogenes at various stages of the production and supply chain, and these pathogens may survive under various storage conditions. The effects of relative humidity, temperature, and duration of storage on the attachment and survival of both pathogens on the surface of tomatoes were investigated. Fresh whole Roma tomatoes were inoculated with a cocktail of Salmonella or L. monocytogenes strains and stored at 5, 12, 25, 30, or 35°C for up to 10 days. Every day during storage, relative humidity and temperature were measured and tomatoes were removed to enumerate pathogens cells that were loosely attached (LA; cells were detached from the tomato surface by rinsing) and strongly attached (SA; sonication was required to detach cells from the tomato surface). The attachment strength (SR) was calculated to express the proportion of surviving SA cells on the tomato surface. The initial levels of Salmonella and L. monocytogenes on the tomato surface after inoculation were 6.6 and 6.5 log CFU per tomato for LA cells and 5.1 and 5.6 log CFU per tomato for SA cells, respectively. For both pathogens, the LA levels were higher (P < 0.05) than the SA levels. The LA and SA levels differed significantly as a function of temperature, relative humidity, and duration of storage. The SR for Salmonella was affected by storage time but not temperature, whereas the SR for L. monocytogenes was affected by storage time and temperature and relative humidity (P < 0.05). An understanding of the attachment and survival of Salmonella and L. monocytogenes on tomatoes stored under various temperature conditions may be useful for preventing or reducing the establishment of pathogens and for designing improved decontamination methods.

Inactivation of Pectobacterium carotovorum subsp. Carotovorum and Dickeya chrysanthemi on the surface of fresh produce using a 222 nm krypton–chlorine excimer lamp and 280 nm UVC light-emitting diodes

Pectobacterium carotovorum subsp. carotovorum and Dickeya chrysanthemi have been reported to cause soft-rot diseases to fresh produces. The aim of this research was to investigate the inactivation efficacy of a 222 nm KrCl excimer lamp and 280 nm UVC-LED against P. carotovorum subsp. carotovorum and D. chrysanthemi on fresh produces. When samples were subjected to UVC treatment by a excimer lamp or UVC-LED at 450 mJ/cm2, it was observed that soft-rot bacteria on the surface of iceberg lettuce, strawberry, and tomato were reduced by a maximum of 5, 3, and 5 log units, respectively. The surface properties of fresh products, such as hydrophobicity, roughness, and topographic image, were analyzed under the hypothesis that the characteristics of the sample surface affected the inactivation efficacy of the excimer lamp and UVC-LED. It was determined that there was an inverse correlation between the surface roughness and inactivation efficacy of UVC treatment. The texture properties of samples were not significantly different (P > 0.05) from those of untreated samples. The results of this research substantiate that the excimer lamp and UVC-LED can be applied to decontamination processes for inactivating soft-rot bacteria, thereby prolonging the shelf life of fresh produce and reducing economic losses.

Strength of Salmonella attachment on apple and tomato surfaces: Effect of antimicrobial treatments on population reduction and inactivation

Presence of bacteria and its survival on produce surfaces is important in developing non-thermal processing interventions for food safety. In this study, whole apples and tomatoes were individually inoculated with Salmonella bacteria at 4.6 log CFU/g and 3.0 log CFU/g, respectively and then allowed to air dry in a laminar flow biological hood (NuareTM, Plymouth, MN, USA) before antimicrobial treatments at 0, 20 min, 30 min, 60min, 120 min, 360 min, 540 min and 1440 min post inoculation, respectively. After washing treatments, strength of attachment for Salmonella bacteria on apple and tomato surfaces was calculated. The efficacy of a new antimicrobial solution developed in our laboratory, was compared to 1.5% hydrogen peroxide and 200 ppm chlorine treatments. The relative strength of Salmonella attached on whole apples and tomatoes averaged 0.22 and 0.25, respectively. The 200-ppm chlorine and 1.5% hydrogen peroxide (H 2 O2) treatments achieved 2.8 log CFU/g inactivation, while the new antimicrobial solution led to 3.9 log CFU/g and 2.9 log CFU/g reductions on tomatoes and apple surfaces, respectively. Strength of bacterial attachment increased at 360 min post inoculation. The attachment phenomena impacted the activity of all antimicrobial treatments in reducing bacterial populations, except the organic acid solution.

Effects of pulsed light and aerosolized formic acid treatments on inactivation of Salmonella enterica on cherry tomato, reduction of microbial loads, and preservation of fruit quality

Fresh produce remains the leading cause of foodborne illness outbreaks. Novel nonthermal technologies are needed to reduce the risk of pathogen contamination. The objective of this study was to develop a novel intervention technology exploiting integration of high intensity short time (10 s) pulsed light (PL) and aerosolized formic acid (AFA) for inactivation of Salmonella and maintenance of quality of cherry tomato. Smooth surface of tomatoes, inoculated with a cocktail containing three serotypes of Salmonella enterica, was treated with PL for 10 s followed by 2 min treatment with 1% AFA. Non-inoculated tomatoes were used to study the treatment effects on native microflora and quality. PL delivered significant inactivation at low doses. An optimal 10 s PL treatment equivalent to a dose of 10.5 J/cm2, provided 2.2 log CFU/g reduction while a 2 min exposure in 1% AFA antimicrobial yielded comparatively low, 1.7 log CFU/g reductions of Salmonella on tomato. The combination treatments of PL (10 s) followed by 1% AFA (2 min) provided additive inactivation yielding 4.2 log CFU/g reductions (P ≤ 0.05) of the pathogen. During cold storage (10 °C) the survivor population declined further providing 4.8 log CFU/g reductions on day 21. The combination PL-AFA treatment significantly reduced the native microbiota of tomato and also hindered their growth while in storage for three weeks. Mold and yeast (M&Y) spoilage organism populations declined to below the detection level. Furthermore, the quality factors as firmness and color of tomatoes were not significantly affected by the combination treatments. The treatment boosted the redness appearance of tomatoes indicating favorable consumer acceptability. Overall, our results demonstrate that combination of PL and AFA treatment could potentially be used as a novel approach to enhance microbial safety and quality of tomatoes.

Antimicrobial activity of chitosan film containing nanocomposite of Trachyspermum ammi (ajwain) seed oil loaded Halloysite nanotubes against foodborne pathogenic microorganisms

Ajwain seed oil (ASO) is a volatile organic compound possessing antimicrobial properties against a wide range of microorganisms. Halloysite nanotubes (Hal) are aluminosilicate natural clay minerals with about 200–2000 nm in length and diameters between 10-50 nm. The structure of Hal allows a sustained release of antimicrobial agents to microbial cells which can be beneficial in the food packaging field. In this work, we loaded ASO into Sodium hydroxide (NaOH) treated Hal and further incorporated it with chitosan to develop an innovative antimicrobial food packaging nanocomposite film. The developed nanocomposite films were characterized by UV–visible spectroscopy, Fourier transform infrared spectroscopy, Raman Spectroscopy, Differential scanning calorimetry, Field emission scanning electron microscopy and X-ray diffraction. The antimicrobial properties of the developed nanocomposites were studied against two bacterial strains (Escherichia coli and Bacillus mojavensis) and two fungus strains (Aspergillus niger and Aspergillus flavus) potential food spoilage microorganisms. The nanocomposite (ASO-NaOH-Hal) prevented the growth of Esherichia coli up to 99%, Bacillus mojavensis up to 95%, Aspergillus niger about 97%, and Aspergillus flavus about 97% at concentrations of 5 mg/ml, 7 mg/ml, 5 mg/ml and 5 mg/ml, respectively. And the chitosan film containing ASO-NaOH-Hal presented a clear zone of inhibition against the above-mentioned bacterial strains and inhibited the growth of fungus on the tomato's surfaces therefore, this nanocomposite film could find application in the food packaging field owing to its antimicrobial and antioxidant properties.

Rapid Trace Detection of Pesticide Residues on Tomato by Surface-Enhanced Raman Spectroscopy and Flexible Tapes

The non-judicious use of pesticides in agro-food poses a severe threat to food safety and human health. As an emerging chromatographic fingerprint provider, surface-enhanced Raman spectroscopy analysis (SERS) sheds bright light on sensitive and nondestructive detection of pesticide residues. This research proposed a novel strategy to detect three-pesticide residues (thiabendazole, carbendazim, and chlorpyrifos) on tomato peel based on the flexible and sticky SERS substrate. After selecting the best commercial adhesive tape (3M9080), the SERS substrate was constructed by optimizing the parameters in the preparation process of AuNPs. Therefore, a new simple “tape-wrapped SERS” way for pesticide residue analysis was established with a simple procedure of “absorption, separation, and drop addition.” Based on chemometrics method, the limit of semiquantitative detection was 20, 36, and 80 ng/cm2 for thiabendazole, carbendazim, and chlorpyrifos, respectively, on tomato surface, which indicated that the proposed method could meet the requirement of actual application with a large prospect in agro-food safety detection.

Efficacy of a Mixed Peroxyorganic Acid Antimicrobial Wash Solution against Salmonella, Escherichia coli O157:H7, or Listeria monocytogenes on Cherry Tomatoes

A study was conducted to evaluate a new organic mixed peroxyacid solution produce wash composed of a combination of organic acids (lactic acid and one or more fruit acids) and hydrogen peroxide for activity against foodborne pathogens. The mixed peroxyacid was challenged against Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes in suspension or on the surface of dip-inoculated cherry tomatoes. Cherry tomatoes were also treated with 8 ppm of free chlorine in the form of sodium hypochlorite. When tested against planktonic cells of Salmonella and E. coli O157:H7 in pure culture for 120 s, these pathogens were reduced by 7.5 and 7.1 log CFU/mL, respectively, by the 0.40% peroxyacid solution, and L. monocytogenes was decreased by 5.0 log CFU/mL by the 0.80% solution. When cherry tomatoes were dip inoculated and treated with 8 ppm of free chlorine, Salmonella and E. coli O157:H7 populations decreased by 2.5 and 2.6 log CFU/g, respectively; these reductions were not significantly different from those obtained after sterile water rinses. However, the 1.0% peroxyacid solution reduced the same microorganisms by 3.8 and 3.4 log CFU/g, respectively, which was significantly greater (P < 0.05) than the reductions achieved by the 2-min sterile water rinse. For tomatoes dip inoculated with L. monocytogenes, populations were reduced by 3.5 log CFU/g by the 1.0% peroxyacid solution, which was significantly greater (P < 0.05) than reductions achieved by 8 ppm of free chlorine (2.6 log CFU/g) or sterile water (1.7 log CFU/g). These results indicate that this peroxyacid combination is an effective organic antimicrobial agent for preventing cross-contamination during the washing of cherry tomatoes and can inactivate S. enterica, E. coli O157:H7, and L. monocytogenes by up to 3.8, 3.4, and 3.5 log CFU/g, respectively.

Antibiotic resistance in soil and tomato crop irrigated with freshwater and two types of treated wastewater

Agricultural use of treated wastewater (TWW) is an effective means to reduce freshwater (FW) consumption. However, there is a growing concern regarding the potential dissemination of antibiotic resistance elements by TWW irrigation. We hypothesized that higher levels of antibiotic resistance genes (ARGs) would be detected in soil and crops irrigated with TWW compared to FW irrigation. To test our prediction, samples of water (FW, secondary TWW, and tertiary TWW), irrigated soils, and crops (tomato) surface wash were collected during two consecutive growing seasons. The ARGs conferring resistance to sulfonamide, fluoroquinolone, penicillin, erythromycin and tetracycline were quantified in the samples, alongside Class 1 integron-integrase and the bacterial 16 S rRNA encoding genes. Contrary to our hypothesis, ARGs in the irrigation water were not propagated to either the irrigated soil, or the tomato. The tomato surface wash featured a variety of ARGs that were undetected in neither the waters nor the irrigated soils. Therefore, we cautiously question the link between irrigation water quality and the soil and produce resistomes.

Aureobasidium pullulans S-2 reduced the disease incidence of tomato by influencing the postharvest microbiome during storage

Biological control of postharvest fruit diseases by antagonistic microorganisms is considered an effective alternative to chemical fungicides. The influence of microbial antagonists on the fruit-associated microbiome provides a new perspective for the in-depth study of the antagonistic mechanism. In this study, the biocontrol effect of A. pullulans S-2 against postharvest diseases of tomatoes was investigated. At the same time, the fungal and bacterial microbiota on tomato surfaces were investigated by high-throughput sequencing. The results showed that A. pullulans S-2 could inhibit the decay incidence, maintain fruit firmness and reduce weight loss of tomato. In addition, the treatment group could maintain higher titratable acidity, ascorbic acid and lycopene content than the control group. More dramatic changes in fungal diversity than in bacterial diversity were observed in the microbiota after the application of A. pullulans S-2. Aureobasidium was significantly enriched in the treatment group, while Cladosporium, Mycosphaerella, Alternaria and Penicillium decreased compared to the control group. Pantoea, Brevibacterium, Brachybacterium, Serratia, Glutamicibacter and Pseudomonas also showed significant differences between the two groups. This study shows that the application of A. pullulans S-2 leads to changes in the bacterial and fungal community that can inhibit plant pathogens and reduce the incidence of fruit diseases. It provides new insights into the dynamics of the surface microbiome of tomato after treatment with microbial antagonists.

Coherently designed sustainable SERS active substrate of Ag/TiO2 hybrid nanostructures for excellent ultrasensitive detection of chlorpyrifos pesticide on the surface of grapes and tomatoes

Pesticide residues contain extremely noxious elements and are found on the surface of fruits which cause serious problems to human health even at very low concentrations. From this, we developed a facile strategy and scientifically confirmed the structure, surface engineering, and spectroscopy properties of Ag/TiO2 hybrid nanostructures (nanoplates, nanorods) modified SERS active substrate for detection of chlorpyrifos on the surface of grapes and tomatoes via paste, peel off, and paste again approach. Benefiting from it, Ag/TiO2 nanorods as SERS active substrate exposed a significant enhancement for ultrasensitive performance with a dynamic linear range of 10−2 to 10-9 M. The low detection limit (LOD) was found to be 2 ng/cm2 for grapes and 5 ng/cm2 for tomatoes based on signal to noise ratio (S/N=3) with correlation coefficient R2 = 0.9983 and 0.9966, which lower than the reported values. Interestingly, the Ag/TiO2 modified SERS active sensor was able to demonstrate excellent ultra-sensitivity, reusability for the real sample analysis and could cheer up the commercial sensor for on-site detection of pesticide on fruits and vegetables in the near scenario.

Contrasting responses to soil and water salinity in stomata and canopy traits produced convergence of water-use in tomatoes (Solanum esculentum) and okra (Abelmoschus esculentus): application to water management.

Salinity constrains agricultural sustainability and crops differ in their response. We tested the hypothesis that contrasting responses in canopy and stomatal traits to salinity will cause convergence of water-use in okra and tomato. Stomata were found almost exclusively (>90%) on the lower leaf surface of tomato, but okra produced ~30% of stomata on the upper leaf surface. While salinity reduced the magnitudes of canopy and stomata traits in tomato, stomata traits were either unaffected or enhanced in okra. Salinity reduced the rates and duration of stomatal conductance (gs ) in both crops, more severely in tomato, in which gs was restricted to early mornings in contrast to its bell-shape trend in okra. The superiority of okra in its stomata traits was compensated by the larger plant canopies in tomato, resulting in both daytime canopy transpiration and total plant water-use within 17% and 28%, respectively, of each other for the two crops. A tight stomatal control of transpiration that minimised use of water and its uptake from the soil conferred a superior salinity tolerance on tomato over okra. In both crops, stomata density (D) was inversely correlated with stomata area (A), while water-use was positively correlated with plant leaf area, in addition to D and A in tomato; gs was also correlated with stomata area index in tomato. Differences in water-use for both crops were relatively narrow, despite the several-fold differences in their canopy and stomata traits. Under saline conditions, irrigation intervals should be long for tomato but short for okra. © 2021 Society of Chemical Industry.

Trifluralin recognition using touch-based fingertip: Application of wearable glove-based sensor toward environmental pollution and human health control.

Monitoring of herbicides and pesticides in water, food, and the environment is essential for human health, and this requires low-cost, portable devices for widespread deployment of this technology. For the first time, a wearable glove-based electrochemical sensor based on conductive Ag nano-ink was developed for the on-site monitoring of trifluralin residue on the surface of various substrates. Three electrode system with optimal thicknesses was designed directly on the finger surface of a rubber glove. Then, fabricated electrochemical sensor used for the direct detection of trifluralin in the range of 0.01 μM to 1 mM on the surface of tomato and mulberry leaves using square wave voltammetry (SWV) and difference pulse voltammetry technique. The obtained LLOQ was 0.01 μM, which indicates the suitable sensitivity of this sensor. On the other hand, this sensor is portable, easy to use, and has a high environmental capability that can be effective in detecting other chemical threats in the soil and water environment.

Transcription of Listeria monocytogenes Key Virulence Genes on Tomato, Cucumber and Carrot

The aim of the present study was to assess the transcription of Listeria monocytogenes key virulence genes, namely sigB, prfA, hly, plcA, plcB, inlA, inlB, inlC and inlJ during subsistence on the surface of tomato, cucumber and carrot stored at 4, 10 and 30 °C for 0, 0.5, 6 and 24 h. Gene relative transcription was assessed through reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The results obtained, indicated that the relative transcription of plcA, plcB and inlB was more affected during subsistence on cucumber surface whereas the relative transcription of sigB, prfA, hly, inlA and inlC was more affected on tomato surface. Subsistence of the pathogen on carrot surface had only marginal effect on the relative transcription of the virulence genes assessed in the present study. In the majority of the cases, the aforementioned effects were dependent on the storage temperature employed.

Antibacterial activity and the physicochemical characteristics of plasma activated water on tomato surfaces

A new technique, plasma activated water (PAW), was used to inactivate bacteria on the tomato surface. The PAW was generated at 60 Watts (W) for 20 min using air flow rates at 6 or 10 standard liter per min (slm) with 1 or 2 plasma jet(s). Tomatoes inoculated with Salmonella Typhimurium, Escherichia coli, or Listeria monocytogenes were treated by the PAW for 30, 60, 90, 120, 150, 180 or 210 s. Significantly higher reductions (p < 0.05) of bacterial populations were obtained with 2 plasma jets. More than 5 log reductions of S. Typhimurium, E. coli, and L. monocytogenes were obtained when treated with 2 acting plasma jets for 30, 180, and 210 s, respectively. When treatment time increased, lower values of pH and higher values of oxidative reduction potential, nitrite, nitrate, ozone, and peroxide were obtained. An analysis of the electron paramagnetic resonance confirmed the generation of reactive oxygen species in PAW. This study showed that PAW was effective against bacteria on tomato surfaces and offered evidences for the antibacterial mechanism of PAW.

Antiviral Effects of Pomegranate Peel Extracts on Human Norovirus in Food Models and Simulated Gastrointestinal Fluids.

Human noroviruses (HuNoV) are the dominant cause of viral gastroenteritis in all age groups worldwide. In this study, we investigated the effects of pomegranate peel extract (PPE) on the reduction of HuNoV in different food models, on surfaces of fresh produce (green onion and cherry tomato), in low-fat milk, and simulated gastrointestinal fluids. The antiviral efficacy of PPE against HuNoV was evaluated by quantifying the number of residual virus genomes using a quantitative reverse transcription PCR (qRT-PCR) assay. Pomegranate peel, considered as a waste product of industrial processing, is known for beneficial health effects and broad antimicrobial activity due to the high content of phenolic compounds and tannins. PPE showed significant antiviral properties against HuNoV both in phosphate-buffered saline (PBS) and simulated gastric fluid. The reduction of HuNoV by pomegranate juice was lower than with PPE, which could be attributed to the lower content of antimicrobial compounds. A pretreatment of cherry tomato and green onion surfaces with PPE significantly reduced the amount of HuNoV particles that adhered to those surfaces during subsequent virus suspension treatment. A detrimental effect of PPE on HuNoV structure was confirmed by transmission electron microscopy. Our results indicate that PPE is a natural antiviral agent effective against food-borne noroviruses.

Investigating the biocontrol potentiality of Wickerhamomyces anomalus against postharvest gray mold decay in cherry tomatoes

Gray mold decay caused by Botrytis cinerea is one of the primary postharvest diseases of cherry tomatoes globally, leading to considerable economic losses. This study aimed to assess the biocontrol efficacy of Wickerhamomyces anomalus against postharvest gray mold decay in cherry tomatoes. The results indicated that W. anomalus significantly reduced the gray mold decay in cherry tomatoes in a concentration-dependent manner without affecting cherry tomatoes' quality. W. anomalus developed rapidly in wounds and on surfaces of cherry tomatoes at both 20 ± 2 °C and 4 ± 2 °C, and reduced the spore germination and germ tube length of B. cinerea in vitro. W. anomalus could adapt to the environment and compete for the nutrients and space against the pathogens. Besides, W. anomalus significantly enhanced the activities of defense-related enzymes in cherry tomatoes, including polyphenoloxidase (PPO), peroxidase (POD), catalase (CAT), and phenylalanine ammonialyase (PAL). Ultimately, the application of W. anomalus induced the disease resistance ability of cherry tomatoes. These findings suggested that W. anomalus could be a promising biocontrol agent to manage the postharvest gray mold decay in cherry tomatoes.