Electron beam inactivation of Tulane virus on fresh produce, and mechanism of inactivation of human norovirus surrogates by electron beam irradiation

Synergistic effects of sequential treatment using disinfectant and e-beam for inactivation of hepatitis a virus on fresh vegetables

Hepatitis A virus (HAV) has adversely affected public health worldwide, causing an economic burden on many countries. Fresh vegetables are reported as a source of HAV infections during production, harvesting, and distribution, which cause the emergence of foodborne illnesses. Therefore, in this study, the synergistic effects of chemical (sodium hypochlorite [NaOCl] and chlorine dioxide [ClO2]) and physical (electron-beam [e-beam] irradiation) sequential treatment for HAV inactivation on fresh vegetables were investigated, and the physicochemical quality changes of vegetables were evaluated after each treatment. On bell pepper and cucumber sequentially treated with NaOCl (50-500 ppm) and e-beam (1-5 kGy), the HAV titer was reduced by 0.19-4.69 and 0.28-4.78 log10 TCID50/mL, respectively. Sequential treatment with ClO2 (10-250 ppm) and e-beam (1-5 kGy) reduced the HAV titer on bell pepper and cucumber by 0.41-4.78 and 0.26-4.80 log10 TCID50/mL, respectively. The sequential treatments steadily decreased the HAV titers on each food by a significant difference (p < 0.05) compared to the controls. The treatment combinations of 500 ppm NaOCl and 3 kGy (e-beam) on bell pepper and 150 ppm NaOCl and 1 kGy (e-beam) on cucumber provided maximum synergistic effects. It was also found that sequential treatment with 50 ppm ClO2 and 5 kGy (e-beam) on bell pepper and 10 ppm ClO2 and 5 kGy (e-beam) on cucumber most efficiently inactivated HAV. Additionally, bell pepper and cucumber showed no significant quality changes (p < 0.05) after the treatment. Therefore, the sequential treatment with NaOCl or ClO2 and e-beam is expected to effectively control HAV on fresh vegetables without changing the food quality compared to either treatment alone.

Research Progress on Biological Accumulation, Detection and Inactivation Technologies of Norovirus in Oysters

Noroviruses (NoVs) are major foodborne pathogens that cause acute gastroenteritis. Oysters are significant carriers of this pathogen, and disease transmission from the consumption of NoVs-infected oysters occurs worldwide. The review discusses the mechanism of NoVs bioaccumulation in oysters, particularly the binding of histo-blood group antigen-like (HBGA-like) molecules to NoVs in oysters. The review explores the factors that influence NoVs bioaccumulation in oysters, including temperature, precipitation and water contamination. The review also discusses the detection methods of NoVs in live oysters and analyzes the inactivation effects of high hydrostatic pressure, irradiation treatment and plasma treatment on NoVs. These non-thermal processing treatments can remove NoVs efficiently while retaining the original flavor of oysters. However, further research is needed to reduce the cost of these technologies to achieve large-scale commercial applications. The review aims to provide novel insights to reduce the bioaccumulation of NoVs in oysters and serve as a reference for the development of new, rapid and effective methods for detecting and inactivating NoVs in live oysters.

Innovative nonthermal technologies for inactivation of emerging foodborne viruses

Various foodborne viruses have been associated with human health during the last decade, causing gastroenteritis and a huge economic burden worldwide. Furthermore, the emergence of new variants of infectious viruses is growing continuously. Inactivation of foodborne viruses in the food industry is a formidable task because although viruses cannot grow in foods, they can survive in the food matrix during food processing and storage environments. Conventional inactivation methods pose various drawbacks, necessitating more effective and environmentally friendly techniques for controlling foodborne viruses during food production and processing. Various inactivation approaches for controlling foodborne viruses have been attempted in the food industry. However, some traditionally used techniques, such as disinfectant-based or heat treatment, are not always efficient. Nonthermal techniques are considered a new platform for effective and safe treatment to inactivate foodborne viruses. This review focuses on foodborne viruses commonly associated with human gastroenteritis, including newly emerged viruses, such as sapovirus and Aichi virus. It also investigates the use of chemical and nonthermal physical treatments as effective technologies to inactivate foodborne viruses.

Inactivation of two SARS-CoV-2 virus surrogates by electron beam irradiation on large yellow croaker slices and their packaging surfaces

The detection of infectious SARS-CoV-2 in food and food packaging associated with the cold chain has raised concerns about the possible transmission pathway of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in foods transported through cold-chain logistics and the need for novel decontamination strategies. In this study, the effect of electron beam (E-beam) irradiation on the inactivation of two SARS-CoV-2surrogate, viruses porcine epidemic diarrhea virus (PEDV) and porcine transmissible gastroenteritis virus (TGEV), in culture medium and food substrate, and on food substrate were investigated. The causes of virus inactivation were also investigated by transmission electron microscopy (TEM) and Quantitative Real-time PCR (QRT-PCR). Samples packed inside and outside, including virus-inoculated large yellow croaker and virus suspensions, were irradiated with E-beam irradiation (2, 4, 6, 8, 10 kGy) under refrigerated (0 °C)and frozen (−18 °C) conditions. The titers of both viruses in suspension and fish decreased significantly (P < 0.05) with increasing doses of E-beam irradiation. The maximum D₁₀ value of both viruses in suspension and fish was 1.24 kGy. E-beam irradiation at doses below 10 kGy was found to destroy the spike proteins of both SARS-CoV-2 surrogate viruses by transmission electron microscopy (TEM) and negative staining of thin-sectioned specimens, rendering them uninfectious. E-beam irradiation at doses greater than 10 kGy was also found to degrade viral genomic RNA by qRT-PCR. There were no significant differences in color, pH, TVB-N, TBARS, and sensory properties of irradiated fish samples at doses below 10 kGy. These findings suggested that E-beam irradiation has the potential to be developed as an efficient non-thermal treatment to reduce SARS-CoV-2 contamination in foods transported through cold chain foods to reduce the risk of SARS-CoV-2 infection in humans through the cold chain.

Quantitative determination of the electron beam radiation dose for SARS-CoV-2 inactivation to decontaminate frozen food packaging

The spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from cold-chain foods to frontline workers poses a serious public health threat during the current global pandemic. There is an urgent need to design concise approaches for effective virus inactivation under different physicochemical conditions to reduce the risk of contagion through viral contaminated surfaces of cold-chain foods. By employing a time course of electron beam exposure to a high titer of SARS-CoV-2 at cold-chain temperatures, a radiation dose of 2 ​kGy was demonstrated to reduce the viral titer from 10^4.5 to 0 median tissue culture infectious dose (TCID₅₀)/mL. Next, using human coronavirus OC43 (HCoV-OC43) as a suitable SARS-CoV-2 surrogate, 3 ​kGy of high-energy electron radiation was defined as the inactivation dose for a titer reduction of more than 4 log units on tested packaging materials. Furthermore, quantitative reverse transcription PCR (RT-qPCR) was used to test three viral genes, namely, E, N, and ORF1ab. There was a strong correlation between TCID₅₀ and RT-qPCR for SARS-CoV-2 detection. However, RT-qPCR could not differentiate between the infectivity of the radiation-inactivated and nonirradiated control viruses. As the defined radiation dose for effective viral inactivation fell far below the upper safe dose limit for food processing, our results provide a basis for designing radiation-based approaches for the decontamination of SARS-CoV-2 in frozen food products. We further demonstrate that cell-based virus assays are essential to evaluate the SARS-CoV-2 inactivation efficiency for the decontaminating strategies.

Inactivation of porcine epidemic diarrhea virus with electron beam irradiation under cold chain conditions

The many instances of COVID-19 outbreaks suggest that cold chains are a possible route for the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, owing to the low temperatures of cold chains, which are normally below 0 °C, there are limited options for virus inactivation. Here, high-energy electron beam (E-beam) irradiation was used to inactivate porcine epidemic diarrhea virus (PEDV) under simulated cold chain conditions. This coronavirus was used as a surrogate for SARS-CoV-2. The possible mechanism by which high-energy E-beam irradiation inactivates PEDV was also explored. An irradiation dose of 10 kGy reduced the PEDV infectious viral titer by 1.68-1.76 log₁₀TCID 50 / 100 μ L in the cold chain environment, suggesting that greater than 98.1% of PEDV was inactivated. E-beam irradiation at 5-30 kGy damaged the viral genomic RNA with an efficiency of 46.25%-92.11%. The integrity of the viral capsid was disrupted at 20 kGy. The rapid and effective inactivation of PEDV at temperatures below freezing indicates high-energy E-beam irradiation as a promising technology for disinfecting SARS-CoV-2 in cold chain logistics to limit the transmission of COVID-19.

Contamination, bioaccumulation mechanism, detection, and control of human norovirus in bivalve shellfish: A review

Human norovirus (HuNoV) is a major foodborne pathogen that causes acute viral gastroenteritis, and bivalve shellfish are one of the main carriers of HuNoV transmission. A comprehensive understanding of bivalve shellfish-related HuNoV outbreaks focusing on contamination factors, bioaccumulation mechanisms, and pre- and post-harvest interventions is essential for the development of effective strategies to prevent contamination of shellfish. This review comprehensively surveys the current knowledge on global contamination and non-thermal treatment of HuNoV in bivalve shellfish. HuNoV contamination in bivalve shellfish is significantly related to the season and water. While evaluating the water quality of shellfish-inhabited waters is a key intervention, the development of non-heat treatment technology to effectively inactivate the HuNoV in bivalve shellfish while maintaining the flavor and nutrition of the shellfish is also an important direction for further research. Additionally, this review explores the bioaccumulation mechanisms of HuNoV in bivalve shellfish, especially the mechanism underlying the binding of histo-blood group antigen-like molecules and HuNoV. The detection methods for infectious HuNoV are also discussed. The establishment of effective methods to rapidly detect infectious HuNoV and development of biological components to inactivate or prevent HuNoV contamination in shellfish also need to be studied further.

Guidance on validation of lethal control measures for foodborne pathogens in foods

Food manufacturers are required to obtain scientific and technical evidence that a control measure or combination of control measures is capable of reducing a significant hazard to an acceptable level that does not pose a public health risk under normal conditions of distribution and storage. A validation study provides evidence that a control measure is capable of controlling the identified hazard under a worst-case scenario for process and product parameters tested. It also defines the critical parameters that must be controlled, monitored, and verified during processing. This review document is intended as guidance for the food industry to support appropriate validation studies, and aims to limit methodological discrepancies in validation studies that can occur among food safety professionals, consultants, and third-party laboratories. The document describes product and process factors that are essential when designing a validation study, and gives selection criteria for identifying an appropriate target pathogen or surrogate organism for a food product and process validation. Guidance is provided for approaches to evaluate available microbiological data for the target pathogen or surrogate organism in the product type of interest that can serve as part of the weight of evidence to support a validation study. The document intends to help food manufacturers, processors, and food safety professionals to better understand, plan, and perform validation studies by offering an overview of the choices and key technical elements of a validation plan, the necessary preparations including assembling the validation team and establishing prerequisite programs, and the elements of a validation report.

Assessment of human norovirus inhibition in cabbage kimchi by electron beam irradiation using RT-qPCR combined with immunomagnetic separation

Cabbage Kimchi, a traditional Korean fermented food, has occasionally been related to acute gastroenteritis caused by human norovirus (HuNoV). The present study examined the inhibitory effects of electron beam (e-beam) irradiation (1, 3, 5, 7, and 10 kGy) on HuNoV GII.4 in suspension or cabbage Kimchi using reverse transcription quantitative polymerase chain reaction combined with immunomagnetic separation (IMS/RT-qPCR). In addition, physicochemical and sensorial analyses were conducted to assess any change in the quality of cabbage Kimchi following e-beam irradiation. Following e-beam irradiation at 1 to 10 kGy, HuNoV significantly decreased to 0.28 to 2.08 log₁₀ copy number/mL in suspension (P < 0.05). HuNoV levels in cabbage Kimchi were also significantly reduced to 0.26 to 1.57 log₁₀ copy number/mL following irradiation with 1 to 10 kGy (P < 0.05) compared to positive control (6.0 log₁₀ copy number/mL). The D-values for 1 log₁₀ reduction (90% inhibition) of HuNoV in suspension and cabbage Kimchi were 4.94 and 6.96 kGy of e-beam, respectively. The pH and acidity in the irradiated cabbage Kimchi were 4.41 to 4.58 and 0.61% to 0.71%, respectively, indicating that e-beam did not affect the optimal pH or acidity. Although a slight increase of greenness was observed in the leaf portion of cabbage Kimchi irradiated with 7 to 10 kGy of e-beam, this color change was minimal and went undetected by panelists in the sensorial evaluation. The five properties of sensorial quality assessed were no different in the irradiated Kimchi sample compared with the control sample (nonirradiated cabbage Kimchi). Therefore, this study suggests that ≥6.96 kGy of e-beam could be applied in the cabbage Kimchi industry to obtain >90% of HuNoV without affecting the quality. PRACTICAL APPLICATION: As the most representative food in Korea, Kimchi needs the sanitation technology that can inhibit viral infection. Our findings suggest that e-beam irradiation can be used to reduce HuNoV effectively in Kimchi without changes in sensorial quality.

Inactivation of hepatitis A virus and murine norovirus on surfaces of plastic, steel and raspberries using steam-ultrasound treatment

The leading causes of foodborne viral disease outbreaks are human norovirus and hepatitis A virus (HAV). Their environmental persistence enables contamination of kitchen surfaces and crops often consumed raw, such as berries. Many decontamination procedures are inefficient and unsuitable for surfaces of industrial kitchen environments and soft fruits. In this study, we investigated the efficiency of a novel surface decontamination technology, combining steam and ultrasound (steam-ultrasound). Plastic, steel or raspberry surfaces were spiked with the norovirus surrogate, murine norovirus (MNV), and HAV, and steam-ultrasound treated at 85, 90 and 95 °C for 0-5 s. Post treatment viruses were titrated for survival by plaque assay and for genome stability by real-time quantitative PCR (RT-qPCR) of nucleic acid extracts. Survival of viruses were estimated in a log-linear model and the treatment time requirements for each decimal reduction (D value) in viral survival were calculated. The estimated D values of MNV or HAV were 0.4-0.2 or 1.1-0.8 s on plastic, 0.9-0.7 or 1.4-0.8 s on steel and 1.6-1.7 or 3.2-4.7 s on raspberries. No clear trend of genome reduction was observed with tested treatment parameters. Raspberries treated up to 4 s retained its natural texture and visual appeal similar to untreated controls whilst monitored for 7 days. In conclusion, steam-ultrasound treatment can within seconds reduce the titre of foodborne viruses on surfaces of plastic, steel and raspberries. This may particularly benefit industrial scale production of soft fruits for raw consumption and for swift non-hazardous decontamination of industrial kitchen surfaces.

Inactivation of Murine Norovirus and Fecal Coliforms by Ferrate(VI) in Secondary Effluent Wastewater

Ferrate(VI) (Fe^VIO₄², Fe(VI)) is an emerging oxidant/disinfectant to treat a wide range of contaminants and microbial pollutants in wastewater. This study describes the inactivation of murine norovirus (MNV) by Fe(VI) in phosphate buffer (PB) and secondary effluent wastewater (SEW). The decay of Fe(VI) had second-order kinetics in PB while Fe(VI) underwent an initial demand followed by first-order decay kinetics in SEW. The Chick-Watson inactivation kinetic model, based on integral CT (ICT) dose, well fitted the inactivation of MNV in both PB and SEW. In PB, the values of the inactivation rate constant (k_d) decreased with an increase in pH, which was related to the reaction of protonated Fe(VI) species (HFeO₄^-) with MNV. Higher k_d was observed in SEW than in PB. The inactivation of indigenous fecal coliforms (FC) in SEW was also measured. A two-population double-exponential model that accounted for both dispersed and particle-associated FC well fitted the inactivation data with determined k_d and particle-associated inactivation rate constant (k_p). Results show that Fe(VI) was more effective in inactivating dispersed FC than MNV. The MNV inactivation results obtained herein, coupled with the detailed modeling, provide important information in designing an Fe(VI) wastewater disinfection process.

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.

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.

Microneedles for vaccine delivery: challenges and future perspectives

Vaccine delivery to the skin using conventional needles is associated with needle-stick injuries and needle-phobia, which are all major obstacles to vaccination. The development of microneedles has enabled to overcome these limitations and as a result viral, DNA and bacterial vaccines have been studied for the delivery into the skin. Research has shown the superiority of microneedle vaccination over conventional needles in terms of immunogenicity, vaccine stability and dose-sparing abilities in animals and humans. Additional research on improving vaccine stability and delivering vaccines to other areas of the body besides the skin is ongoing as well. Thus, this review paper describes current advances in microneedles as a delivery system for vaccines as well as future perspectives for this research field.

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.

Inactivation of human norovirus and Tulane virus in simple media and fresh whole strawberries by ionizing radiation

Human norovirus (NoV) is a major cause of fresh produce-associated outbreaks and human NoV in irrigation water can potentially lead to viral internalization in fresh produce. Therefore, there is a need to develop novel intervention strategies to target internalized viral pathogens while maintaining fresh produce quality. In this study electron beam (E-beam) and gamma radiation were evaluated for efficacy against a human NoV GII.4 strain and Tulane virus (TV). Virus survival following ionizing radiation treatments was determined using direct quantitative reverse transcriptase PCR (RT-qPCR), the porcine gastric mucin magnetic bead (PGM-MB) binding assay followed by RT-qPCR, and plaque assay. In simple media, a high dose of E-beam treatment was required to completely abolish the receptor binding ability of human NoV (35.3kGy) and TV (19.5-24.1kGy), as assessed using the PGM-MB binding assay. Both human NoV and TV were more susceptible to gamma irradiation than E-beam, requiring 22.4kGy to achieve complete inactivation. In whole strawberries, no human NoV or TV RNA was detected following 28.7kGy of E-beam treatment using the PGM-MB binding assay. Overall, human NoV and TV are highly resistant to ionizing radiation and therefore the technology may not be suitable to eliminate viruses in fresh produce at the currently approved levels. In addition, the PGM-MB binding assay is an improved method to detect viral infectivity compared to direct RT-qPCR.

Thermal Inactivation of Enteric Viruses and Bioaccumulation of Enteric Foodborne Viruses in Live Oysters (Crassostrea virginica)

Human enteric viruses are among the main causative agents of shellfish-associated outbreaks. In this study, the kinetics of viral bioaccumulation in live oysters and the heat stabilities of the predominant enteric viruses were determined both in tissue culture and in oyster tissues. A human norovirus (HuNoV) GII.4 strain, HuNoV surrogates (murine norovirus [MNV-1], Tulane virus [TV]), hepatitis A virus (HAV), and human rotavirus (RV) bioaccumulated to high titers within oyster tissues, with different patterns of bioaccumulation for the different viruses. We tested the thermal stability of each virus at 62, 72, and 80°C in culture medium. The viruses can be ranked from the most heat resistant to the least stable as follows: HAV, RV, TV, MNV-1. In addition, we found that oyster tissues provided protection to the viruses during heat treatment. To decipher the mechanism underlying viral inactivation by heat, purified TV was treated at 80°C for increasing time intervals. It was found that the integrity of the viral capsid was disrupted, whereas viral genomic RNA remained intact. Interestingly, heat treatment leading to complete loss of TV infectivity was not sufficient to completely disrupt the receptor binding activity of TV, as determined by the porcine gastric mucin-magnetic bead binding assay. Similarly, HuNoV virus-like particles (VLPs) and a HuNoV GII.4 strain retained some receptor binding ability following heat treatment. Although foodborne viruses have variable heat stability, 80°C for >6 min was sufficient to completely inactivate enteric viruses in oysters, with the exception of HAV.

Control of human norovirus surrogates in fresh foods by gaseous ozone and a proposed mechanism of inactivation

Fresh produce is a major concern for transmission of foodborne enteric viruses as it is normally consumed with no heat treatments and minimal other processing to ensure safety. Commonly used sanitizers are ineffective at removing foodborne viruses from fresh produce. Thus the use of gaseous ozone for viral inactivation was investigated. Ozone has great potential for improved food safety because of four benefits: It is a potent sanitizer, it is effective against a wide range of microorganisms, it is permitted for food use as regulated by the U.S. FDA and several other nations, and it spontaneously decomposes to oxygen leaving no residue. This study determined the effectiveness of gaseous ozone for the sanitization of two norovirus surrogates (MNV-1 and TV) from both liquid media and popular fresh foods where viral contamination is common-lettuce and strawberries. Foods were treated with gaseous ozone at 6% wt/wt ozone in oxygen for 0, 10, 20, 30, and 40 min, and surviving viruses were quantified by viral plaque assay. Our results showed that gaseous ozone inactivated norovirus in both liquid media and fresh produce in a dose-dependent manner. These results are promising because ozone treatment significantly reduced two important norovirus surrogates in both liquid and food matrices. Viruses are generally more resistant to sanitation treatments than bacteria, thus gaseous ozone is an effective means to improve fresh produce safety.