Enhanced removal of a human norovirus surrogate from fresh vegetables and fruits by a combination of surfactants and sanitizers

Assessing the virucidal activity of essential oils against feline calicivirus, a non-enveloped virus used as surrogate of norovirus

Norovirus (NoV) causes serious gastrointestinal disease worldwide and is regarded as an important foodborne pathogen. Due the difficulties of in vitro cultivation for human NoV, alternative caliciviruses (i.e., feline calicivirus, FCV, or murine NoV) have long been used as surrogates for in vitro assessment of the efficacy of antivirals. Essential oils (EOs) are natural compounds that have displayed antimicrobial and antioxidant properties. We report in vitro the virucidal efficacy of four EOs, Melissa officinalis L. EO (MEO), Thymus vulgaris L. EO (TEO), Rosmarinus officinalis L. EO (REO), and Salvia officinalis L. EO (SEO) against FCV at different time contacts (10, 30 min, 1, 4 and 8 h). At the maximum non-cytotoxic concentration and at 10- and 100- fold concentrations over the cytotoxic threshold, the EOs did not decrease significantly FCV viral titers. However, MEO at 12,302.70 μg/mL exhibited a significant efficacy decreasing the viral titer by 0.75 log10 Tissue Culture Infectious Dose (TCID50)/50 μl after 10 min as compared to virus control. In this study, virucidal activity of four EOs against FCV, was investigated. A lack of virucidal efficacy of TEO, REO and SEO at different compound concentrations and time contacts against FCV was observed whilst MEO was able to significantly decrease FCV titer.

Norovirus: An Overview of Virology and Preventative Measures

Norovirus (NoV) is an enteric non-enveloped virus which is the leading cause of gastroenteritis across all age groups. It is responsible for around 200,000 deaths annually and outbreaks are common in small communities such as educational and care facilities. 40% of all NoV outbreaks occur in long-term and acute-care facilities, forming the majority of outbreaks. Nosocomial settings set ideal environments for ease of transmission, especially due to the presence of immunocompromised groups. It is estimated to cost global economies around £48 billion a year, making it a global issue. NoV is transmitted via the faecal-oral route and infection with it results in asymptomatic cases or gastrointestinal disease. It has high mutational rates and this allows for new variants to emerge and be more resistant. The classification system available divides NoV into 10 genogroups and 49 genotypes based on whole amino acid sequencing of VP1 capsid protein and partial sequencing of RdRp, respectively. The most predominant genotypes which cause gastroenteritis in humans include GI.1 and GII.4, where GII.4 is responsible for more extreme clinical implications such as hospitalisation. In addition, GII.4 has been responsible for 6 pandemic strains, the last of which is the GII.4 Sydney (2012) variant. In recent years, the successful cultivation of HuNoV was reported in stem cell-derived human intestinal enteroids (HIEs), which promises to assist in giving a deeper understanding of its underlying mechanisms of infection and the development of more personalized control measures. There are no specific control measures against NoV, therefore common practices are used against it such as hand washing. No vaccine is available, but the HIL-214 candidate passed clinical phase 2b and shows promise.

Evaluation of water-assisted UV-C light and its additive effect with peracetic acid for the inactivation of Listeria monocytogenes, Salmonella enterica and murine norovirus on whole and fresh-cut strawberries during shelf-life

BACKGROUND

The purpose of the present study was to examine the inactivation of Salmonella enterica (50 μL; 10⁹  CFU g^-1 ), Listeria monocytogenes (50 μL; 10⁹  CFU g^-1 ), and murine norovirus (MNV-1; 50 μL; 10⁷ 50% tissue culture infectious dose (TCID₅₀ ) mL^-1 ) on whole and fresh-cut strawberries after 2 min disinfection treatments (water (H₂ O), chlorine 200 mg L^-1 (NaClO), water-assisted ultraviolet-C (UV-C) (WUV), and the combination WUV and 40 mg L^-1 of PA (WUV + PA)) in a water tank (15 L) equipped with 4 UV-C lamps (17.2 W each), and after 7 days of cold storage (4 and 10 °C). For MNV-1, dry UV-C treatment (DUV) was also tested. For all UV-C treatments, an irradiation dose of 1.3 kJ m^-2 was used.

RESULTS

When strawberries were washed with WUV, L. monocytogenes and S. enterica were reduced by 2.8 and 2.2 log CFU g^-1 , respectively. The addition of 40 mg L^-1 of PA to WUV (WUV + PA) increased the reduction range of L. monocytogenes and S. enterica by 1.9 and 0.8 log, respectively. Regarding the wash water, no pathogens were recovered after the WUV + PA treatment (detection limit 50 CFU mL^-1 ). Depending on storage conditions (7 days at 4 or 10 °C), reductions observed were 0.5 to 2.0 log for S. enterica and 0.5 to 3.0 log for L. monocytogenes. The reductions in MNV-1 titer after disinfection treatments ranged from 1.3 to 1.7 log. No significant differences between storage conditions were observed for MNV-1: titers did not decline or were reduced up to 0.3 log after 7 days of cold storage.

CONCLUSION

The three-way action for disinfecting strawberries by UV-C irradiation and PA, plus the physical removal of the microorganisms by agitated water, are effective against foodborne pathogens on strawberries and water wash. During storage, WUV had a larger impact on the inactivation kinetics of S. enterica. Storage had little impact on MNV-1 inactivation. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Impact of Theaflavins-Enriched Tea Leaf Extract TY-1 against Surrogate Viruses of Human Norovirus: In Vitro Virucidal Study

Using an effective natural virucidal substance may be a feasible approach for preventing food-borne viral contamination. Here, the virucidal efficacy of theaflavins (TFs)-enriched tea leaf extract (TY-1) against feline calicivirus (FCV) and murine norovirus (MNV), surrogates of human norovirus (HuNoV), was evaluated. The virus solutions were mixed with various dosages of TY-1 and incubated at 25 °C for different contact times. TY-1 reduced the viral titer of both surrogate viruses in a time- and dosage-dependent manner. A statistically significant reduction in the viral titer of FCV by 5.0 mg/mL TY-1 and MNV by 25.0 mg/mL TY-1 was observed in 10 s and 1 min, respectively. Furthermore, TY-1 reduced the viral titer of FCV and MNV on the dry surface in 10 min. The multiple compounds in TY-1, including TFs and catechins, contributed to its overall virucidal activity. Furthermore, the effect of TY-1 on viral proteins and genome was analyzed using Western blotting, RT-PCR, and transmission electron microscopy. TY-1 was found to promote the profound disruption of virion structures, including the capsid proteins and genome. Our finding demonstrates the potential of using TY-1 as a nature-derived disinfectant in food processing facilities and healthcare settings to reduce viral load and HuNoV transmission.

Glycyrrhizic Acid Inhibits SARS-CoV-2 Infection by Blocking Spike Protein-Mediated Cell Attachment

Glycyrrhizic acid (GA), also known as glycyrrhizin, is a triterpene glycoside isolated from plants of Glycyrrhiza species (licorice). GA possesses a wide range of pharmacological and antiviral activities against enveloped viruses including severe acute respiratory syndrome (SARS) virus. Since the S protein (S) mediates SARS coronavirus 2 (SARS-CoV-2) cell attachment and cell entry, we assayed the GA effect on SARS-CoV-2 infection using an S protein-pseudotyped lentivirus (Lenti-S). GA treatment dose-dependently blocked Lenti-S infection. We showed that incubation of Lenti-S virus, but not the host cells with GA prior to the infection, reduced Lenti-S infection, indicating that GA targeted the virus for infection. Surface plasmon resonance measurement showed that GA interacted with a recombinant S protein and blocked S protein binding to host cells. Autodocking analysis revealed that the S protein has several GA-binding pockets including one at the interaction interface to the receptor angiotensin-converting enzyme 2 (ACE2) and another at the inner side of the receptor-binding domain (RBD) which might impact the close-to-open conformation change of the S protein required for ACE2 interaction. In addition to identifying GA antiviral activity against SARS-CoV-2, the study linked GA antiviral activity to its effect on virus cell binding.

Organic Acid Sanitizers for Natamycin and Other Fungicides in Recirculating Application Systems for Citrus Postharvest Decay Management

Natamycin is a new postharvest biofungicide for citrus and some other fruit crops in the United States that can be effectively used in recycling drench or flooder treatments. These applications necessitate sanitation of the fungicide solution to ensure that it remains free from contamination by bacteria that are potentially human pathogens. During in vitro experiments, heated (48°C) citric acid (1,100 or 2,200 μg/ml) amended with sodium dodecylbenzenesulfonate (SDBS) (60 or 120 μg/ml, respectively) significantly reduced the viability of a nonpathogenic strain of Escherichia coli in natamycin solutions by >5 log₁₀ compared with the control. During laboratory studies with Penicillium digitatum-inoculated lemon fruit, 1,000 μg/ml of natamycin mixed with 1,000 μg/ml of lactic acid or citric acid and with or without SDBS (55 μg/ml) effectively and significantly reduced green mold. Natamycin mixed with lactic acid at ≥2,000 μg/ml, however, caused fruit injury, resulting in browning and rind pitting. Natamycin was incompatible with peroxyacetic acid, resulting in reduced efficacy against green mold. Sodium hypochlorite mixed with natamycin lost its toxicity to E. coli; however, the performance of natamycin was not affected. With heated (average 49°C) drench treatments on an experimental packing line, natamycin (1,000 μg/ml), fludioxonil (300 μg/ml), or azoxystrobin (300 μg/ml) mixed with citric acid (1,000 μg/ml) and SDBS (55 μg/ml) were effective against green mold without fruit injury. At a pH between 3.6 and 3.8, citric acid-SDBS significantly reduced the viability of E. coli by approximately 4 log₁₀ in mixtures with fludioxonil or azoxystrobin, but not with natamycin. However, natamycin at 1,000 μg/ml mixed with 2,000 μg/ml of citric acid and SDBS (55 μg/ml) significantly reduced E. coli counts by >4 log₁₀ within 4 min when the pH was maintained between 3.0 and 3.3, and the efficacy of the fungicide was retained. The use of citric acid with a surfactant can be a viable alternative sanitation method for natamycin in citrus packinghouses utilizing heated recirculating fungicide systems.

Improved real-time quantitative reverse transcription PCR detection of norovirus following removal of inhibitors

Human norovirus (HuNoV) is an important enteric virus that can cause large gastroenteritis outbreaks via the fecal-oral route from contaminated water and produce. Real-time quantitative reverse transcription PCR (RT-qPCR) is the only method to apply the routine detection of HuNoV in various samples, however, inhibitors present in the samples can affect the accuracy and sensitivity of RT-qPCR results. Here, we suggest an inhibitor-removal treatment for two types of noroviruses using two commercial kits. Two types of water sample (surface and seawater) and four types of produce (green onions, lettuces, radishes, and strawberries) were evaluated. The recovery efficiencies of noroviruses in water samples clearly increased in surface and seawater samples with the inhibitor-removal treatment compared to untreated samples. Moreover, murine norovirus-1 was well recovered from the four types of produce with the inhibitor-removal treatment. The mean recovery efficiencies of HuNoV genogroup II genotype 4 in lettuces and strawberries were also increased in the treated samples. Therefore, we suggest that the inhibitor-removal treatment could be useful for improving the accuracy and sensitivity of RT-qPCR methods for noroviruses in water and produce.

Evaluation of SDS and GRAS liquid disinfectants for mitigation of hepatitis A virus contamination of berries

AIM

To evaluate generally recognized as safe (GRAS) liquid wash formulations against hepatitis A virus-contaminated strawberries and blackberries in order to identify a formulation suitable for reducing virus contamination.

METHODS AND RESULTS

Formulations included the surfactant sodium dodecyl sulfate (SDS; 0·5% w/v) by itself, and in combination, with lactic acid (LA; 0·5% v/v), levulinic acid (LVA; 0·5% v/v) and 3 ppm aqueous chlorine dioxide (ClO₂ ). After contamination and drying overnight, the average total extracted contamination for both untreated strawberries and blackberries was 4·4 log PFU. Three successive distilled H₂ O only treatments reduced total contamination by up to 1·8 log PFU for both strawberries and blackberries, while wash formulations showed significant (P ≤ 0·05) total reductions ranging from 2·1 to 2·9 log PFU.

CONCLUSIONS

Considering results for both berry types, the combination of ClO₂ and SDS was the most effective. Overall results indicate that adding surfactant and several types of sanitizers to berry wash can enhance HAV reduction on berries.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study indicates that industry could enhance the virologic safety of ready-to-eat berries by the combined use of surfactant and sanitizer.

The Basis of Peracetic Acid Inactivation Mechanisms for Rotavirus and Tulane Virus under Conditions Relevant for Vegetable Sanitation

We determined the disinfection efficacy and inactivation mechanisms of peracetic acid (PAA)-based sanitizer using pH values relevant for vegetable sanitation against rotavirus (RV) and Tulane virus (TV; a human norovirus surrogate). TV was significantly more resistant to PAA disinfection than RV: for a 2-log10 reduction of virus titer, RV required 1 mg/liter PAA for 3.5 min of exposure, while TV required 10 mg/liter PAA for 30 min. The higher resistance of TV can be explained, in part, by significantly more aggregation of TV in PAA solutions. The PAA mechanisms of virus inactivation were explored by quantifying (i) viral genome integrity and replication using reverse transcription-quantitative PCR (RT-qPCR) and (ii) virus-host receptor interactions using a cell-free binding assay with porcine gastric mucin conjugated with magnetic beads (PGM-MBs). We observed that PAA induced damage to both RV and TV genomes and also decreased virus-receptor interactions, with the latter suggesting that PAA damages viral proteins important for binding its host cell receptors. Importantly, the levels of genome-versus-protein damage induced by PAA were different for each virus. PAA inactivation correlated with higher levels of RV genome damage than of RV-receptor interactions. For PAA-treated TV, the opposite trends were observed. Thus, PAA inactivates each of these viruses via different molecular mechanisms. The findings presented here potentially contribute to the design of a robust sanitation strategy for RV and TV using PAA to prevent foodborne disease.IMPORTANCE In this study, we examined the inactivation mechanisms of peracetic acid (PAA), a sanitizer commonly used for postharvest vegetable washing, for two enteric viruses: Tulane virus (TV) as a human norovirus surrogate and rotavirus (RV). PAA disinfection mechanisms for RV were mainly due to genome damage. In contrast, PAA disinfection in TV was due to damage of the proteins important for binding to its host receptor. We also observed that PAA triggered aggregation of TV to a much greater extent than RV. These studies demonstrate that different viruses are inactivated via different PAA mechanisms. This information is important for designing an optimal sanitation practice for postharvest vegetable washing to minimize foodborne viral diseases.

Hurdle Effect of Hot Air Impingement Drying and Surfactant-Sanitizer Wash on Removal of Listeria innocua from Fresh Apples

ABSTRACT

This study investigated the decontamination efficacy of washing treatments for whole fresh apples by using washes containing surfactants, lauric arginate, sodium dodecyl sulfate, and Tween 20, combined with peracetic acid (PAA), followed by hot air impingement drying. Whole fresh apples of selected varieties (Gala and Granny Smith) were inoculated with Listeria innocua (7 log CFU/mL) by using a dipping method, and then dried and subjected to wash treatments with selected washing solutions (H2O, PAA, PAA-lauric arginate, PAA-sodium dodecyl sulfate, and PAA-Tween 20), followed by hot air impingement drying at two different temperature and time conditions, 93°C for 60 s or 121°C for 25 s. The H2O and PAA wash followed by hot air impingement drying led to a maximum 1.5-log reduction of L. innocua on the fruit surface. Adding surfactants increased the effectiveness of washing and drying treatments, resulting in an approximate 2.2-log reduction. Surfactants increased the spreadability and evaporation rate of the washing solutions. Posttreatment changes in apple firmness were assessed during a 21-day storage at 4 and 21°C. The hot air impingement drying had no adverse effect on the firmness of the apples and did not show any further reduction in L. innocua. Washing apples with solutions containing surfactants combined with PAA followed by hot air impingement drying helped to reduce the microbial loads to some extent and may help to reduce drying times significantly.

HIGHLIGHTS

Evaluation of a sanitizing washing step with different chemical disinfectants for the strawberry processing industry

Strawberries are often consumed fresh or only receive minimal processing, inducing a significant health risk to the consumer if contamination occurs anywhere from farm to fork. Outbreaks of foodborne illness associated with strawberries often involve a broad range of microbiological agents, from viruses (human norovirus) to bacteria (Salmonella spp. and Listeria monocytogenes). The addition of sanitizers to water washes is one of the most commonly studied strategies to remove or inactivate pathogens on berries as well as avoid cross contamination due to reuse of process wash water. The risk posed with the safety issues of by-products from chlorine disinfection in the fruit industry has led to a search for alternative sanitizers. We evaluated the applicability of different chemical sanitizers (peracetic acid (PA), hydrogen peroxide (H₂O₂), citric acid (CA), lactic acid (LA) and acetic acid (AA)) for the inactivation of S. enterica, L. monocytogenes and murine norovirus (MNV-1) on strawberries. A control treatment with chlorine (NaClO) (100 ppm) was included. For each sanitizer, different doses (40, 80 and 120 ppm for PA and 1, 2.5 and 5% for H₂O₂, LA, AA and CA) and time (2 and 5 min) were studied in order to optimize the decontamination washing step. The best concentrations were 80 ppm for PA, 5% for H₂O₂ and 2.5% for organic acids (LA, AA and CA) after 2 min treatment. Results indicate that the sanitizers selected may be a feasible alternative to chlorine (100 ppm) for removing selected pathogenic microorganisms (P > 0.05), with reductions about ≥2 log for bacterial strains and ≥ 1.7 log for MNV-1. As the washing water may also increase the microbial counts by cross-contamination, we observed that no pathogenic bacteria were found in wash water after 5% H₂O₂ and 80 ppm PA after 2 min treatment. On the other hand, we also reported reductions about total aerobic mesophyll (TAM) (0.0-1.4 log CFU/g) and molds and yeasts (M&Y) (0.3-1.8 log CFU/g) with all alternative sanitizers tested. Strawberries treated did not shown significant differences about physio-chemical parameters compared to the untreated samples (initial). For this study, the optimal sanitizer selected was PA, due to the low concentration and cost needed and its microbiocidal effect in wash water and fruit. Notwithstanding the results obtained, the effect of PA in combination with other non-thermal technologies such as water-assisted ultraviolet (UV-C) light should be studied in future research to improve the disinfection of strawberries.

Surface Active Agents and Their Health-Promoting Properties: Molecules of Multifunctional Significance

Surface active agents (SAAs) are molecules with the capacity to adsorb to solid surfaces and/or fluid interfaces, a property that allows them to act as multifunctional ingredients (e.g., wetting and dispersion agents, emulsifiers, foaming and anti-foaming agents, lubricants, etc.) in a widerange of the consumer products of various industrial sectors (e.g., pharmaceuticals, cosmetics, personal care, detergents, food, etc.). Given their widespread utilization, there is a continuously growing interest to explore their role in consumer products (relevant to promoting human health) and how such information can be utilized in order to synthesize better chemical derivatives. In this review article, weaimed to provide updated information on synthetic and biological (biosurfactants) SAAs and their health-promoting properties (e.g., anti-microbial, anti-oxidant, anti-viral, anti-inflammatory, anti-cancer and anti-aging) in an attempt to better define some of the underlying mechanism(s) by which they exert such properties.

Roles of Vegetable Surface Properties and Sanitizer Type on Annual Disease Burden of Rotavirus Illness by Consumption of Rotavirus-Contaminated Fresh Vegetables: A Quantitative Microbial Risk Assessment

Enteric viruses are often detected in water used for crop irrigation. One concern is foodborne viral disease via the consumption of fresh produce irrigated with virus-contaminated water. Although the food industry routinely uses chemical sanitizers to disinfect post-harvest fresh produce, it remains unknown how sanitizer and fresh produce properties affect the risk of viral illness through fresh produce consumption. A quantitative microbial risk assessment model was conducted to estimate (i) the health risks associated with consumption of rotavirus (RV)-contaminated fresh produce with different surface properties (endive and kale) and (ii) how risks changed when using peracetic acid (PAA) or a surfactant-based sanitizer. The modeling results showed that the annual disease burden depended on the combination of sanitizer and vegetable type when vegetables were irrigated with RV-contaminated water. Global sensitivity analyses revealed that the most influential factors in the disease burden were RV concentration in irrigation water and postharvest disinfection efficacy. A postharvest disinfection efficacy of higher than 99% (2-log₁₀ ) was needed to decrease the disease burden below the World Health Organization (WHO) threshold, even in scenarios with low RV concentrations in irrigation water (i.e., river water). All scenarios tested here with at least 99.9% (3-log₁₀ ) disinfection efficacy had a disease burden lower than the WHO threshold, except for the endive treated with PAA. The disinfection efficacy for the endive treated with PAA was only about 80%, leading to a disease burden 100 times higher than the WHO threshold. These findings should be considered and incorporated into future models for estimating foodborne viral illness risks.

Outbreaks, occurrence, and control of norovirus and hepatitis a virus contamination in berries: A review

Foodborne enteric viruses, in particular HuNoV and HAV, are the most common cause of the berry-linked viral diseases, and outbreaks around the world, and have become an important concern for health authorities. Despite the increased importance of berry fruits as a vehicle for foodborne viruses, there is limited information concerning the fate of foodborne viruses in the berry supply chain from farm to consumer. A comprehensive understanding of berry-associated viral outbreaks - with a focus on contamination sources, persistence, survival, and the effects of current postharvest and processing interventions and practices - is essential for the development of effective preventative strategies to reduce risk of illness. The purpose of this paper is twofold; (i) to critically review the published literature on the current state of knowledge regarding berry-associated foodborne viral outbreaks and the efficiency of berry processing practices and (ii) to identify and prioritize research gaps regarding practical and effective mechanism to reduce viral contamination of berries. The review found that fecally infected food handlers were the predominant source of preharvest and postharvest pathogenic viral contamination. Current industrial practices applied to fresh and frozen berries demonstrated limited efficacy for reducing the viral load. While maintaining best practice personal and environmental hygiene is a key intervention, the optimization of processing parameters (i.e., freezing, frozen storage, and washing) and/or development of alternative processing technologies to induce sufficient viral inactivation in berries along with retaining sensory and nutritional quality, is also an important direction for further research.

Efficacy of Surfactant Combined with Peracetic Acid in Removing Listeria innocua from Fresh Apples

Large amounts of water used in the apple packing process, the presence of organic matter, and difficult-to-clean equipment are vectors for contaminating apples with foodborne pathogens, such as Listeria monocytogenes. There is a need to develop new cleaning methods for fresh apples and evaluate their antimicrobial efficacy. A series of surfactants of different chemical properties (cationic lauric arginate [LAE], anionic sodium dodecyl sulfate [SDS], and nonionic Tween 20 [T20]) alone and combined with peracetic acid (PAA) were evaluated for their efficiency in the removal of L. innocua, a surrogate of L. monocytogenes, from fresh apples. Whole fresh apples were inoculated with L. innocua (7 log CFU/mL) by a dipping method, dried, and subjected to wash treatments with selected cleaning solutions (water, PAA, PAA-LAE, PAA-SDS, and PAA-T20). The contact angle between the cleaning solutions and the surface of the apples was measured. The antimicrobial activity of the cleaning solutions and the efficacy of the cleaning treatment were evaluated by enumeration of L. innocua from treated apples and visualized by scanning electron microscopy. Stem bowl and calyx cavities of the apple harbored higher bacteria concentrations (∼4.82 log CFU per apple), compared with the equatorial section (∼2.66 log CFU per apple). Addition of 0.1% of selected surfactants led to a significant decrease in surface tension of cleaning solutions and allowed better spreading on the apple surface. Surfactants combined with PAA solution resulted in higher L. innocua reduction compared with PAA alone; however, their efficacy was limited. The most effective cleaning solution was PAA-T20, with reduction of approximately 2.2 log. Scanning electron microscopy imaging confirmed that most bacteria were harbored inside the surface irregularities. PAA alone and with surfactants caused damage and deformation of bacteria cells. Cleaning apples with PAA combined with surfactants may improve microbial safety in whole apples; however, the efficiency of the decontamination treatment can be reduced because of variations in apple morphology.

Free Chlorine Disinfection Mechanisms of Rotaviruses and Human Norovirus Surrogate Tulane Virus Attached to Fresh Produce Surfaces

To fill the knowledge gap on how effective free chlorine is against viral-contaminated produce, we inoculated the surfaces of outdoor- or greenhouse-grown kale and mustard with Rotavirus (RV) or a human norovirus surrogate (Tulane virus, TV) and then disinfected the leaves with free chlorine. Disinfection efficacies for RV strain OSU and Wa were approximately 1-log10 higher when attached to mustard than to kale. Similar disinfection efficacies were observed for TV attached to mustard or kale. When examining TV and RV OSU in suspension (not attached to leaf surfaces), TV was more resistant to free chlorine than RV OSU. Inactivation efficacies were higher for these viruses in suspension versus viruses attached to produce the surface. We also found that free chlorine damaged viral capsids, allowing free chlorine access to viral RNA to damage viral genomes. Exposure to free chlorine at 1.7 ppm over 1 min caused VP8* of RV OSU to lose its ability to bind to its host receptors. TV lost its ability to bind to its receptor only after exposure to free chlorine at 29 ppm over 1 min. Thus, to reduce foodborne viral infections, it is important to consider the differences in virus' reactivity and inactivation mechanisms with free chlorine.

Colletotrichum Gloesporioides Inhibition In Situ by Chitosan-Ruta graveolens Essential Oil Coatings: Effect on Microbiological, Physicochemical, and Organoleptic Properties of Guava (Psidium guajava L.) during Room Temperature Storage

Guava is a fruit appreciated worldwide for its high content of bioactive compounds. However, it is considered a highly perishable fruit, generally attacked by pathogenic species such as the fungi Colletotrichum gloeosporioides, which causes anthracnosis. To diminish the losses caused by pathogenic fungi, coatings of chitosan (CS) with Ruta graveolens essential oil (RGEO) in different concentrations (0.5, 1.0, 1.5% v/v) were applied in situ and their effects on the physical properties and microbiological quality of the guavas were studied. The CS+RGEO coated fruits exhibited better physicochemical behavior and lower microbiological decay as compared to the uncoated guavas, demonstrating the effectiveness of the coatings, especially those with 1.5% of RGEO content. All the fruits coated had greater acceptance and quality than the controls, being more those with essential oil incorporation. In situ investigation of C. gloesporioides infection of guavas demonstrated that the CS+RGEO coated guavas showed a high percentage of inhibition in the development of anthracnose lesions. In the present investigation, an alternative method has been proposed to extend the stability of the guavas fruit up to 12 days with application in the food industry.

Combination of levulinic acid and sodium dodecyl sulfate on inactivation of foodborne microorganisms: A review

The combination of levulinic acid and sodium dodecyl sulfate (SDS) in recent years has shown considerable promise as an antimicrobial intervention. Both ingredients have been designated by the U.S. Food and Drug Administration (FDA) as Generally Recognized as Safe (GRAS) for being used as a flavoring agent and multipurpose food additive, respectively. The use of levulinic acid and SDS alone has limited antimicrobial efficacy on tested microorganisms, and synergism between levulinic acid and SDS has been observed. The postulated mechanism of action of the synergistic effect is presented. The antimicrobial efficacy of levulinic acid plus SDS remains high even when organic materials are present. The other features, including penetration, foamability, and being readily soluble, extend its potential applications to disinfection of difficult-to-access areas and control of foodborne pathogens both in a planktonic state and in a biofilm. These features indicate that the levulinic acid plus SDS combination may have the potential to be applied within the food processing environment on a large scale.

Removal of Grit from Baby Leafy Salad Vegetables by Combinations of Sanitiser and Surfactant

Grit composed of dirt, sand, and small stones adheres to baby leafy salad vegetables during the growing period and can sometimes be difficult to remove with sanitiser only or tap water. For the first time, the effect of a surfactant, sodium dodecyl sulphate (SDS), alone (0.025, 0.05, and 0.1% SDS) and in combination (0.05% SDS) with peroxyacetic acid (40 mg·L−1, PAA), on grit removal, quality, shelf-life, and taste of baby spinach was investigated. Increasing SDS from 0.025 to 0.1% resulted in a 21–50% increase in grit removal from spinach and coral lettuce. Overall, SDS treatments had no effect on microbial growth, colour, and electrolyte leakage during shelf-life. An increase in bruising, sliming, and yellowing scores was also observed regardless of the treatment, reaching an unacceptable score (<3) by d12 for all samples; however, yellowing scores were still within the acceptable range (>3) on d14. There were no differences in sensorial attributes, namely, flavour, aroma, and texture, between baby spinach samples treated with PAA alone or in combination with SDS. These results demonstrate that SDS treatment can be used to increase grit removal from baby leafy salad vegetables without compromising quality.

Decontamination Effect of the Spindle and 222-Nanometer Krypton-Chlorine Excimer Lamp Combination against Pathogens on Apples (Malus domestica Borkh.) and Bell Peppers (Capsicum annuum L.)

In this study, we developed a washing system capable of decontaminating fresh produce by combining the Spindle apparatus, which detaches microorganisms on sample surfaces, and a 222-nm krypton-chlorine excimer lamp (KrCl excilamp) (Sp-Ex) and investigated their decontamination effect against Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes on apple (Malus domestica Borkh.) and bell pepper (Capsicum annuum L.) surfaces. Initial levels of the three pathogens were approximately 108 CFU/sample. Both E. coli O157:H7 and S. Typhimurium were reduced to below the detection limit (2.0 log CFU/sample) after 5 and 7 min of treatment on apple and bell pepper surfaces, respectively. The amounts of L. monocytogenes on apple and bell pepper surfaces were reduced by 4.26 and 5.48 logs, respectively, after 7 min of treatment. The decontamination effect of the Sp-Ex was influenced by the hydrophobicity of the sample surface as well as the microbial cell surface, and the decontamination effect decreased as the two hydrophobicity values increased. To improve the decontamination effect of the Sp-Ex, Tween 20, a surfactant that weakens the hydrophobic interaction between the sample surface and pathogenic bacteria, was incorporated into Sp-Ex processing. It was found that its decontamination effect was significantly (P < 0.05) increased by the addition of 0.1% Tween 20. Sp-Ex did not cause significant quality changes in apple or bell pepper surfaces during 7 days storage following treatment (P > 0.05). Our results suggest that Sp-Ex could be applied as a system to control pathogens in place of chemical sanitizer washing by the fresh-produce industry.IMPORTANCE Although most fresh-produce processing currently controls pathogens by means of washing with sanitizers, there are still problems such as the generation of harmful substances and changes in product quality. A combination system composed of the Spindle and a 222-nm KrCl excilamp (Sp-Ex) developed in this study reduced pathogens on apple and bell pepper surfaces using sanitizer-free water without altering produce color and texture. This study demonstrates the potential of the Sp-Ex to replace conventional washing with sanitizers, and it can be used as baseline data for practical application by industry. In addition, implementation of the Sp-Ex developed in this study is expected not only to meet consumer preference for fresh, minimally processed produce but also to reduce human exposure to harmful chemicals while being beneficial to the environment.

Characterization of conditions for bacteria-human norovirus capsid P protein complex (BPC) binding to and removal from Romaine lettuce extract

Norovirus is a very contagious virus that causes acute gastroenteritis. Contaminated produce is a main vehicle for dissemination of human noroviruses (HuNoVs). As HuNoVs could bind to bacteria effectively, it is highly possible that produce could be contaminated by bacteria-HuNoVs complex. In this study, we used a bacterial-surface-display system to express genogroup I (GI) or genogroup II (GII) HuNoV capsid protein (P protein) on the surface of bacteria. The bacteria-P protein complex (BPC) was used to characterize the conditions for binding to Romaine lettuce extract and removal of the bound BPCs. We demonstrated both GI and GII BPCs could bind to extract from leaf (LE) and vein (VE) effectively. Carbohydrates in LE and VE were involved in GI BPCs binding, and both carbohydrates and proteins were involved in GII BPCs binding. Saliva from both type A and O secretors could completely block binding of both BPCs to LE and VE. Saliva from type B secretors only partially blocked binding of GII but not GI BPCs to LE and VE. However, LE- and VE-bound BPCs could not be reversely removed by washing solution containing free HBGAs from saliva. The binding of GI BPCs to LE and VE was enhanced when pH was below pI (6.1) of GI and reduced when pH was above pI of GI (p < 0.05). The optimal binding for GII BPCs to LE and VE occurred at pI (6.4) of GII. All LE- or VE-bound BPCs could be reversely removed by washing with low (3.0-5.0) or high (9.0-10.0) pH buffer. The effect of ionic strength (NaCl and MgCl2, from zero to 100 g/L) on binding of BPCs to LE and VE was tested. The optimal ionic strength for binding of BPCs to LE and VE was 10.0 g/L (GI) and 5.0 g/L (GII) for NaCl, and 5.0 g/L for MgCl2. LE- and VE-bound BPCs could be reversely removed by washing with high ionic solutions. All LE- or VE- bound BPCs could be released when washed with NaCl concentrations of above 75.0 g/L (GI) and 25.0 g/L (GII), or with MgCl2 concentrations of above 75.0 g/L (GI) and 50.0 g/L (GII). Binding of BPCs to LE and VE was inhibited in the presence of Tween-80 (nonionic surfactant) as low as 0.05% (v/v). All LE- and VE-bound BPCs could be reversed by Tween-80 concentrations over 0.1% (v/v). The study provided important parameters for BPCs binding to and removal from lettuce extract.

Evaluation of Inactivating Norovirus, Hepatitis A, and Listeria monocytogenes on Raspberries by Sanitizer Spray

HIGHLIGHTS

Chlorine and PAA spray reduced MNV and L. monocytogenes from raspberries by <1.0 log. Residual PAA on raspberries further reduced MNV and Listeria during postspray frozen storage. PAA decayed more slowly than active chlorine on raspberry surfaces. The data suggest that PAA could aid in risk reduction of pathogens on raspberries.

Antimicrobial Particle-Based Novel Sanitizer for Enhanced Decontamination of Fresh Produce

Microbial food safety of raw or minimally processed fresh produce is a significant challenge. The current sanitation processes are effective for inactivation of bacteria in wash water but have limited efficacy (<2 log/g reduction) for inactivation of microbes on the surfaces of fresh produce. This study demonstrates a novel concept to enhance effectiveness of chlorine using a particle-based sanitizer to improve decontamination of fresh produce. In this concept, enhanced effectiveness is achieved by localized high concentration of chlorine bound to the surfaces of silica particles and improved surface contact of microparticles with the produce surface using mechanical shear during a washing process. The results of this study demonstrate that 500 ppm active chlorine can be bound to the surfaces of modified silica particles. These modified particles maintain over 90% of their initial chlorine content during extended storage in aqueous solution and provide improved inactivation of both Escherichia coli O157:H7, Listeria innocua, and Pseudomonas fluorescens in the presence of organic content in contrast to conventional chlorine sanitizer. The modified particles exhibit effective sanitation of fresh produce (>5-log reduction) in the presence of relatively high organic content (chemical oxygen demand of 500 mg/liter), demonstrating a potential to address a significant unmet need to improve fresh produce sanitation. The particle-based sanitizer had no significant effect on the quality of fresh lettuce.IMPORTANCE The limitation of current sanitation processes for inactivation of microbes on the surfaces of fresh produce is due to nonspecific consumption of sanitizers by reactions with the food matrix and complexity of surface chemistries and structural features of produce surfaces. This study demonstrates a novel approach to enhance sanitation effectiveness of fresh produce using a particle-based sanitizer. The particle-based sanitizer concept provides localized high concentration delivery of chlorine to the surfaces of fresh produce and enables more than 5 logs of inactivation of inoculated bacteria on fresh produce surfaces without significant changes in produce quality. The results of this study illustrate the potential of this approach to address the unmet need for improving sanitation of fresh produce. Further validation of this approach using a scaled-up produce washing system will enable commercialization of this novel concept.

Foodborne viruses: Detection, risk assessment, and control options in food processing

In a recent report by risk assessment experts on the identification of food safety priorities using the Delphi technique, foodborne viruses were recognized among the top rated food safety priorities and have become a greater concern to the food industry over the past few years. Food safety experts agreed that control measures for viruses throughout the food chain are required. However, much still needs to be understood with regard to the effectiveness of these controls and how to properly validate their performance, whether it is personal hygiene of food handlers or the effects of processing of at risk foods or the interpretation and action required on positive virus test result. This manuscript provides a description of foodborne viruses and their characteristics, their responses to stress and technologies developed for viral detection and control. In addition, the gaps in knowledge and understanding, and future perspectives on the application of viral detection and control strategies for the food industry, along with suggestions on how the food industry could implement effective control strategies for viruses in foods. The current state of the science on epidemiology, public health burden, risk assessment and management options for viruses in food processing environments will be highlighted in this review.

Enhanced Removal of Norovirus Surrogates, Murine Norovirus and Tulane Virus, from Aqueous Systems by Zero-Valent Iron

Viral contamination can compromise the safety of water utilized for direct consumption, produce irrigation, and postharvest washing of produce. Zero-valent iron (ZVI) is used commercially for chemical remediation of water and has been demonstrated to remove some biological contaminants from water in laboratory and field studies. This study investigated the efficacy of ZVI to remove human norovirus surrogates, Tulane virus (TV) and murine norovirus (MNV), from water and to characterize the reversibility and nature of viral association with ZVI. Genomic material of TV and MNV recovered from the effluent of inoculated water treatment columns containing a 1:1 mixture of ZVI and sand was 2 and 3 log, respectively, less than that recovered from the effluent of treatment columns containing only sand. Elution buffers (citrate buffers, pH 4 and 7, and virus elution buffer, pH 9.5, with and without added 1 M NaCl) did not increase recovery of infectious TV and MNV from ZVI as compared with elution with water alone. TV-inoculated lettuce washed with water in the presence of ZVI yielded 1.5 to 2 log fewer infectious TV from washwater as compared with lettuce washed with water alone or in the presence of sand. These data demonstrate the enhanced removal of human norovirus surrogates, TV and MNV, from water by ZVI and provide indications that unrecovered viruses are not readily disassociated from ZVI by buffers of various pH and ionic strength. These findings warrant further investigation into larger-scale simulations of water remediation of viral contaminants for potential application in the treatment of water used for drinking, irrigation, and food processing.

Norovirus: The Burden of the Unknown

Human noroviruses (HNoVs) are primarily transmitted by the fecal-oral route, either by person-to-person contact, or by ingestion of contaminated food or water as well as by aerosolization. Moreover, HNoVs significantly contribute to foodborne diseases being the causative agent of one-fifth of acute gastroenteritis worldwide. As a consequence of globalization, transnational outbreaks of foodborne infections are reported with increasing frequency. Therefore, in this review, state-of-the-art information regarding molecular procedures for human norovirus detection in food as well common food processing technologies have been summarized. Besides, the purpose of this chapter is to consolidate basic information on various aspects of HNoVs and to summarize food processing technologies that can potentially be applied in the food industry.

Efficacy of Combination Treatment with Sodium Metasilicate and Sodium Hypochlorite for Inactivation of Norovirus on Fresh Vegetables

In recent years, fresh vegetables have frequently been associated with the foodborne transmission of enteric viruses, such as human norovirus (NoV). Therefore, several studies have focused on developing methods to inactivate foodborne viruses for preventing outbreaks of foodborne illnesses. Sodium hypochlorite (NaOCl) is commonly used as a disinfectant, but results in undesirable effects on the appearance and taste of foods and can generate toxic byproducts when it exceeds the allowable concentration. Here, we evaluated the efficacy of a range of NaOCl concentrations (50-1000 ppm) for reducing the amounts of human NoV (NoV GII.4) on lettuce (Lactuca sativa), celery (Apium graveolens L.), and white cabbage (Brassica oleracea ssp. capitata). In addition, the combination treatment of NaOCl and sodium metasilicate (SMS, 0.1-0.5%) pentahydrate was evaluated for its ability to decrease the populations of NoV GII.4 in the three food samples. An immunomagnetic separation procedure combined with reverse transcription quantitative polymerase chain reaction was used for virus detection. For lettuce, celery, and cabbage, the NoV GII.4 recovery rates were 57.3% ± 6.5%, 52.5% ± 1.7%, and 60.3% ± 3.9%, respectively, using a glycine/NaCl elution buffer (0.25 M glycine/0.14 M NaCl, pH 9.5). The reductions of NoV GII.4 were 3.17, 3.06, and 3.27 log10 genomic copies/μL for lettuce, celery, and cabbage, respectively, at 1000 ppm NaOCl, while a reduction of ∼3 log10 genomic copies/μL was obtained when the samples were treated with a combination of 100 ppm NaOCl and 0.4% SMS pentahydrate. Taken together, these results demonstrated that combined treatment with NaOCl and SMS pentahydrate was an efficient strategy to reduce the concentration of NaOCl for control of NoV GII.4 contamination in fresh vegetables.

Surfactant-Enhanced Organic Acid Inactivation of Tulane Virus, a Human Norovirus Surrogate

Combination treatments of surfactants and phenolic or short-chain organic acids (SCOA) may act synergistically or additively as sanitizers to inactive foodborne viruses and prevent outbreaks. The purpose of this study was to investigate the effect of gallic acid (GA), tannic acid, p-coumaric acid, lactic acid (LA), or acetic acid (AA), in combination with sodium dodecyl sulfate (SDS), against Tulane virus (TV), a surrogate for human norovirus. An aqueous stock solution of phenolic acids or SCOA with or without SDS was prepared and diluted in a twofold dilution series to 2× the desired concentration with cell growth media (M119 plus 10% fetal bovine serum). The solution was inoculated with an equal proportion of 6 log PFU/mL TV with a treatment time of 5 min. The survival of TV was quantified using a plaque assay with LLC-MK2 cells. The minimum virucidal concentration was 0.5:0.7% (v/v) for LA-SDS at pH 3.5 (4.5-PFU/mL reduction) and 0.5:0.7% (v/v) AA-SDS at pH 4.0 (2.6-log PFU/mL reduction). GA and SDS demonstrated a minimum virucidal concentration of 12.5 mM GA-SDS at pH 7.0 (0.2:0.3% GA-SDS) with an 0.8-log PFU/mL reduction and 50 mM GA-SDS (0.8:1.4% GA-SDS at pH 7.0) increased log reduction to 1.6 log PFU/mL. The combination treatments of AA or LA with SDS at pH 7.0 did not produce significant log reduction, nor did individual treatments of tannic acid, GA, p-coumaric acid, AA, LA, or SDS. This study demonstrates that a surfactant, such as SDS, aids in the phenolic acid and SCOA toxicities against viruses. However, inactivation of TV by combination treatments is contingent upon the pH of the sanitizing solution being lower than the pK_a value of the organic acid being used. This information can be used to develop sanitizing washes to disinfect food contact surfaces, thereby aiding in the prevention of foodborne outbreaks.

Differential MS2 Interaction with Food Contact Surfaces Determined by Atomic Force Microscopy and Virus Recovery

Enteric viruses are recognized as major etiologies of U.S. foodborne infections. These viruses are easily transmitted via food contact surfaces. Understanding virus interactions with surfaces may facilitate the development of improved means for their removal, thus reducing transmission. Using MS2 coliphage as a virus surrogate, the strength of virus adhesion to common food processing and preparation surfaces of polyvinyl chloride (PVC) and glass was assessed by atomic force microscopy (AFM) and virus recovery assays. The interaction forces of MS2 with various surfaces were measured from adhesion peaks in force-distance curves registered using a spherical bead probe preconjugated with MS2 particles. MS2 in phosphate-buffered saline (PBS) demonstrated approximately 5 times less adhesion force to glass (0.54 nN) than to PVC (2.87 nN) (P < 0.0001). This was consistent with the virus recovery data, which showed 1.4-fold fewer virus PFU recovered from PVC than from glass after identical inoculations and 24 h of cold storage. The difference in adhesion was ascribed to both intrinsic chemical characteristics and the substrate surface porosity (smooth glass versus porous PVC). Incorporating a surfactant micellar solution of sodium dodecyl sulfate (SDS) into the PBS reduced the adhesion force for PVC (∼0 nN) and consistently increased virus recovery by 19%. With direct and indirect evidence of virus adhesion, this study illustrated a two-way assessment of virus adhesion for the initial evaluation of potential means to mitigate virus adhesion to food contact surfaces.IMPORTANCE The spread of foodborne viruses is likely associated with their adhesive nature. Virus attachment on food contact surfaces has been evaluated by quantitating virus recoveries from inoculated surfaces. This study aimed to evaluate the microenvironment in which nanometer-sized viruses interact with food contact surfaces and to compare the virus adhesion differences using AFM. The virus surrogate MS2 demonstrated less adhesion force to glass than to PVC via AFM, with the force-contributing factors including the intrinsic nature and the topography of the contact surfaces. This adhesion finding is consistent with the virus recoveries, which were determined indirectly. Greater numbers of viruses were recovered from glass than from PVC, after application at the same levels. The stronger MS2 adhesion onto PVC could be interrupted by incorporating a surfactant during the interaction between the virus and the contact surface. This study increases our understanding of the virus adhesion microenvironment and indicates ways to mitigate virus adhesion onto contact surfaces.

Inactivation of Human Norovirus Genogroups I and II and Surrogates by Free Chlorine in Postharvest Leafy Green Wash Water

Human noroviruses (hNoVs) are a known public health concern associated with the consumption of leafy green vegetables. While a number of studies have investigated pathogen reduction on the surfaces of leafy greens during the postharvest washing process, there remains a paucity of data on the level of treatment needed to inactivate viruses in the wash water, which is critical for preventing cross-contamination. The objective of this study was to quantify the susceptibility of hNoV genotype I (GI), hNoV GII, murine norovirus (MNV), and bacteriophage MS2 to free chlorine in whole leaf, chopped romaine, and shredded iceberg lettuce industrial leafy green wash waters, each sampled three times over a 4-month period. A suite of kinetic inactivation models was fit to the viral reduction data to aid in quantification of concentration-time (CT) values. Results indicate that 3-log10 infectivity reduction was achieved at CT values of less than 0.2 mg · min/liter for MNV and 2.5 mg · min/liter for MS2 in all wash water types. CT values for 2-log10 molecular reduction of hNoV GI in whole leaf and chopped romaine wash waters were 1.5 and 0.9 mg · min/liter, respectively. For hNoV GII, CT values were 13.0 and 7.5 mg · min/liter, respectively. In shredded iceberg wash water, 3-log10 molecular reduction was not observed for any virus over the time course of experiments. These findings demonstrate that noroviruses may exhibit genogroup-dependent resistance to free chlorine and emphasize the importance of distinguishing between genogroups in hNoV persistence studies.IMPORTANCE Postharvest washing of millions of pounds of leafy greens is performed daily in industrial processing facilities with the intention of removing dirt, debris, and pathogenic microorganisms prior to packaging. Modest inactivation of pathogenic microorganisms (less than 2 log10) is known to occur on the surfaces of leafy greens during washing. Therefore, the primary purpose of the sanitizing agent is to maintain microbial quality of postharvest processing water in order to limit cross-contamination. This study modeled viral inactivation data and quantified the free-chlorine CT values that processing facilities must meet in order to achieve the desired level of hNoV GI and GII reduction. Disinfection experiments were conducted in industrial leafy green wash water collected from a full-scale fresh produce processing facility in the United States, and hNoV GI and GII results were compared with surrogate molecular and infectivity data.

Microbiological risk infection assessment using QMRA in agriculture systems in Côte d'Ivoire, West Africa

Poor wastewater management that results from a lack of appropriate sanitation infrastructure contributes to increasing health risks in urban areas in Côte d'Ivoire. We assessed the health risks associated with the use of wastewater for watering salad destined for human consumption, to help local authorities in developing appropriate risk mitigation measures for Yamoussoukro, the political capital of Côte d'Ivoire. We applied a stochastic approach based on quantitative microbiological risk assessment (QMRA), focusing on wastewater for farming activities and salad consumption at the household level. Farming activities rely on a large degree on contaminated water and are conducted without any protection. The QMRA highlights that the poor quality of watering water increased the microbiological risk of the two assessed groups of urban farmers and individual households. The annual risk of infection due to watering wastewater in the city is estimated at 0.01 per person per year (pppy) for Giardia lamblia and 0.2 pppy for Escherichia coli O157:H7. The annual risk from salad consumption is 0.01 pppy for G. lamblia and 0.9 pppy for E. coli O157:H7. Both the annual risks from farming activities and salad consumption were higher than the tolerable standard of risk of 10^-4 pppy as defined by the World Health Organization. There is a need to conduct a risk analysis and a cost-effectiveness study on intervention to improve public health and the livelihoods of the producers which are women in majority in Yamoussoukro.

Escherichia coli removal from model substrates: Underlying mechanism based on nanofluid structural forces

Understanding the interactions between bacteria and solid surfaces that result in bacterial adhesion and removal is of immense importance for reducing foodborne illness outbreaks. A nanofluid formulation comprised of a sodium dodecyl sulfate (SDS) micellar aqueous solution in the presence of an organic acid (as a pH controller) was used to test the E. coli K12 removal from two substrates, polyvinylchloride (PVC) and partially hydrophobic glass. We investigated the bacterial removal efficacy based on the combined effect of the nanofluid's structural forces and bacterial isoelectric point. To quantify the bacteria-PVC coverage, we used fluorescence microscope. The Langmuir isotherm at the low volume fraction was applied to estimate the adsorption energy of E. coli K12. We obtained a value of about 2.5±0.2kT. This value compared favorably with the value of 2.1kT reported previously for E. coli NCTC 9002 (Vanloosdrecht et al., 1989). We applied the dynamic light scattering method to estimate the radius of the gyration of E. coli K12. The radius of the gyration was used to estimate the limit of surface area covered by the bacterium and compared it to the surface area measured from the image taken with fluorescence microscope. We found that they are in good agreement with each other. We modeled the nanofluid oscillatory structural energy against the E. coli K12 adsorption energy by applying the statistical mechanics approach. Based on the model prediction, the oscillatory interaction energy was estimated at the vertex between a bacterium and the substrate (i.e., the wedge film's interaction energy at one particle layer). The evaluated film's repulsive energy due to the oscillatory structural forces (OSF) was about 15.6±4.4kT of the 0.02M SMNF (the SDS micellar nanofluid formulation) and several times higher than the bacterial adsorption energy, 2.5±0.2kT. The OSF of the 0.06M SMNF was measured by AFM (the oscillatory decay force curve). The period and number of oscillations versus distance was annualized and used to obtain information for the effective size of the nanoparticles and nanofluid's effective volume fraction. These findings suggest that the OSF is capable of bacteria/microorganism removal from contaminated substrates.

Effect of Leaf Surface Chemical Properties on Efficacy of Sanitizer for Rotavirus Inactivation

The use of sanitizers is essential for produce safety. However, little is known about how sanitizer efficacy varies with respect to the chemical surface properties of produce. To answer this question, the disinfection efficacies of an oxidant-based sanitizer and a new surfactant-based sanitizer for porcine rotavirus (PRV) strain OSU were examined. PRV was attached to the leaf surfaces of two kale cultivars with high epicuticular wax contents and one cultivar of endive with a low epicuticular wax content and then treated with each sanitizer. The efficacy of the oxidant-based sanitizer correlated with leaf wax content as evidenced by the 1-log10 PRV disinfection on endive surfaces (low wax content) and 3-log10 disinfection of the cultivars with higher wax contents. In contrast, the surfactant-based sanitizer showed similar PRV disinfection efficacies (up to 3 log10) that were independent of leaf wax content. A statistical difference was observed with the disinfection efficacies of the oxidant-based sanitizer for suspended and attached PRV, while the surfactant-based sanitizer showed similar PRV disinfection efficacies. Significant reductions in the entry and replication of PRV were observed after treatment with either disinfectant. Moreover, the oxidant-based-sanitizer-treated PRV showed sialic acid-specific binding to the host cells, whereas the surfactant-based sanitizer increased the nonspecific binding of PRV to the host cells. These findings suggest that the surface properties of fresh produce may affect the efficacy of virus disinfection, implying that food sanitizers should be carefully selected for the different surface characteristics of fresh produce.

IMPORTANCE

Food sanitizer efficacies are affected by the surface properties of vegetables. This study evaluated the disinfection efficacies of two food sanitizers, an oxidant-based sanitizer and a surfactant-based sanitizer, on porcine rotavirus strain OSU adhering to the leaf epicuticular surfaces of high- and low-wax-content cultivars. The disinfection efficacy of the oxidant-based sanitizer was affected by the surface properties of the vegetables, while the surfactant-based sanitizer was effective for both high- and low-wax leafy vegetable cultivars. This study suggests that the surface properties of vegetables may be an important factor that interacts with disinfection with food sanitizers of rotaviruses adhering to fresh produce.

Detection of human adenoviruses in organic fresh produce using molecular and cell culture-based methods

The consumption of organic fresh produce has increased in recent years due to consumer demand for healthy foods without chemical additives. However, the number of foodborne outbreaks associated with fresh produce has also increased. Contamination of food with enteric viruses is a major concern because the viruses have a low infectious dose and high persistence in the environment. Human adenovirus (HAdV) has been proposed as a good marker of faecal contamination. Therefore, the aim of this study was to evaluate the efficiency of the plaque assay (PA), real time PCR (qPCR) and integrated cell culture-RT-qPCR (ICC-RT-qPCR) for the recovery of HAdV from artificially and naturally contaminated fresh produce. Organic lettuce, strawberries and green onions were selected because these fresh products are frequently associated with foodborne outbreaks. The virus extraction efficiencies from artificially contaminated samples varied from 2.8% to 32.8% depending on the food matrix and the quantification method used. Although the HAdV recoveries determined by qPCR were higher than those determined by PA and ICC-RT-qPCR, PA was defined as the most reproducible method. The qPCR assays were more sensitive than the PA and ICC-RT-qPCR assays; however, this technique alone did not provide information about the viability of the pathogen. ICC-RT-qPCR was more sensitive than PA for detecting infectious particles in fresh produce samples. HAdV genome copies were detected in 93.3% of the analysed naturally contaminated samples, attesting to the common faecal contamination of the fresh produce tested. However, only 33.3% of the total samples were positive for infectious HAdV particles based on ICC-RT-qPCR. In conclusion, this study reported that HAdV can be an efficient viral marker for fresh produce contamination. Good detection of infectious HAdV was obtained with the ICC-RT-qPCR and PA assays. Thus, we suggest that the ICC-RT-qPCR and PA assays should be considered when quantitative microbial risk assessment (QMRA) studies are required and to establish reliable food safety guidelines.

Salmonella and Escherichia coli O157:H7 Inactivation, Color, and Bioactive Compounds Enhancement on Raspberries during Frozen Storage after Decontamination Using New Formula Sanitizer Washing or Pulsed Light

Berries are normally washed before they are frozen. Washing with sanitizer and treatment with pulsed light (PL) were studied for their effectiveness to inactivate foodborne pathogens on raspberries during frozen storage, while maintaining or enhancing major quality parameters. Raspberries were inoculated with Salmonella or Escherichia coli O157:H7 and then underwent a washing treatment with citric acid plus sodium dodecyl sulfate (CA+SDS) or citric acid plus thymol (CA+THY) or treatment with PL (dry PL, water-assisted [wet] PL, and PL-SDS). Pathogen survival was determined immediately after treatments and during frozen storage at -20°C for 3 months. Washing with CA+SDS or CA+THY significantly reduced Salmonella (by 3.6 and 3.2 log CFU/g, respectively) and E. coli O157:H7 (by 4.1 and 3.7 log CFU/g, respectively). At the end of storage, washing with CA+SDS reduced Salmonella to 0.6 log CFU/g and E. coli O157:H7 to 0.5 log CFU/g; washing with CA+THY reduced Salmonella to 0.9 log CFU/g and E. coli O157:H7 to 0.5 log CFU/g. PL-SDS showed decontamination efficacy on raspberries, with 0.7 log CFU/g Salmonella and 0.9 log CFU/g E. coli O157:H7 surviving at the end of storage; in comparison, in the control, 1.6 log CFU/g Salmonella and 1.5 log CFU/g E. coli O157:H7 survived. Pathogen survival in raspberries that had been washed or treated with PL-SDS was significantly lower than in untreated raspberries. Major quality parameters, including color, total phenolic content, total anthocyanin content, total bacterial count, and total yeast and mold counts, were evaluated on raspberries immediately after treatments and during frozen storage. Redness increased in PL-treated raspberries. At the end of storage, PL-treated raspberries had significantly higher total phenolic content and total anthocyanin content compared with control samples. Washing with sanitizers and treatment with PL decreased the total bacterial count and total yeast and mold counts on raspberries and maintained the low counts. Our findings suggest that washing with a sanitizer or treatment with PL could be used to process frozen raspberries for enhanced food safety and quality.

Efficacy of oxidizing disinfectants at inactivating murine norovirus on ready-to-eat foods

Noroviruses are the leading cause of foodborne illness, and ready-to-eat foods are frequent vehicles of their transmission. Studies of the disinfection of fruits and vegetables are becoming numerous. It has been shown that strong oxidizing agents are more effective than other chemical disinfectants for inactivating enteric viruses. The aim of this study was to evaluate the efficacy of oxidizing disinfectants (sodium hypochlorite, chloride dioxide and peracetic acid) at inactivating noroviruses on fruits and vegetables, using a norovirus surrogate, namely murine norovirus 3, which replicates in cell culture. Based on plaque assay, solutions of peracetic acid (85 ppm) and chlorine dioxide (20 ppm) reduced the infectivity of the virus in suspension by at least 3 log10 units after 1 min, while sodium hypochlorite at 50 ppm produced a 2-log reduction. On the surface of blueberries, strawberries and lettuce, chlorine dioxide was less effective than peracetic acid and sodium hypochlorite, which reduced viral titers by approximately 4 logs. A surprising increase in the efficacy of sodium hypochlorite on surfaces fouled with artificial feces was noted.

Utility of Bayesian networks in QMRA-based evaluation of risk reduction options for recycled water

BACKGROUND

Quantitative microbial risk assessment (QMRA), the current method of choice for evaluating human health risks associated with disease-causing microorganisms, is often constrained by issues such as availability of required data, and inability to incorporate the multitude of factors influencing risk. Bayesian networks (BNs), with their ability to handle data paucity, combine quantitative and qualitative information including expert opinions, and ability to offer a systems approach to characterisation of complexity, are increasingly recognised as a powerful, flexible tool that overcomes these limitations.

OBJECTIVES

We present a QMRA expressed as a Bayesian network (BN) in a wastewater reuse context, with the objective of demonstrating the utility of the BN method in health risk assessments, particularly for evaluating a range of exposure and risk mitigation scenarios. As a case study, we examine the risk of norovirus infection associated with wastewater-irrigated lettuce.

METHODS

A Bayesian network was developed following a QMRA approach, using published data, and reviewed by domain experts using a participatory process.

DISCUSSION

Employment of a BN facilitated rapid scenario evaluations, risk minimisation, and predictive comparisons. The BN supported exploration of conditions required for optimal outcomes, as well as investigation of the effect on the reporting nodes of changes in 'upstream' conditions. A significant finding was the indication that if maximum post-treatment risk mitigation measures were implemented, there was a high probability (0.84) of a low risk of infection regardless of fluctuations in other variables, including norovirus concentration in treated wastewater.

CONCLUSION

BNs are useful in situations where insufficient empirical data exist to satisfy QMRA requirements and they are exceptionally suited to the integration of risk assessment and risk management in the QMRA context. They allow a comprehensive visual appraisal of major influences in exposure pathways, and rapid interactive risk assessment in multifaceted water reuse scenarios.

Characterization and control of surfactant-mediated Norovirus interactions

Understanding of the colloidal interactions of Norovirus particles in aqueous medium could provide insights on the origins of the notorious stability and infectivity of these widespread viral agents. We characterized the effects of solution pH and surfactant type and concentration on the aggregation, dispersion, and disassembly of Norovirus virus-like particles (VLPs) using dynamic light scattering, electrophoretic light scattering, and transmission electron microscopy. Owing to net negative surface charge of the VLPs at neutral pH, low concentrations of cationic surfactant tend to aggregate the VLPs, whereas low concentrations of anionic surfactant tend to disperse the particles. Increasing the concentration of these surfactants beyond their critical micelle concentration leads to virus capsid disassembly and breakdown of aggregates. Non-ionic surfactants, however, had little effect on virus interactions and likely stabilized them additionally in suspension. The data were interpreted on the basis of simple models for surfactant binding and re-charging of the virus capsid. We used zeta potential data to characterize virus surface charge and interpret the mechanisms behind these demonstrated surfactant-virus interactions. The fundamental understanding and control of these interactions will aid in practical formulations for virus inactivation and removal from contaminated surfaces.