Evaluation of Steady-State Gaseous Chlorine Dioxide Treatment for the Inactivation of Tulane virus on Berry Fruits

Ultralow temperature high pressure processing enhances inactivation of norovirus surrogates

High pressure processing (HPP) is a powerful non-thermal method for inactivating pathogens. Human norovirus and genetically-related caliciviruses are moderately sensitive to temperatures above 0 °C with >400 MPa (MPa) or higher required to inactivate multiple logs of virus. Sensitivity of murine norovirus (MNV) and Tulane virus (TV) to ice phase transitions was evaluated using ultra low temperature HPP. Identical samples containing MNV or TV were either equilibrated to +1.5 °C (thawed) or -40 °C (frozen) 24 h prior to pressurization. All samples (thawed and frozen) were then placed in a pre-chilled chamber which was then rapidly filled with -40 °C chamber fluid. Samples were immediately pressurized for 5 min at 200, 250 or 300 MPa. Controls were not pressurized. For samples that were thawed and then pressurized in 40 °C chamber fluid, the MNV average log reduction at 200 MPa was 4.4, while >6.1 log reduction (non-detectable) was achieved at 250 and 300 MPa. TV samples averaged 2.3, 5 and 4.3 log reduction at 200, 250, and 300 MPa respectively. For samples that were frozen and then pressurized in 40 °C chamber fluid, the MNV average log reductions were 2.3, 3.2 and 4.2 at 200 MPa, 250 MPa and 300 MPa, respectively, while TV samples averaged 0.81, 2.3 and 1.7 log reductions at 200, 250, and 300 MPa, respectively. Inactivation of TV within oysters at these pressures was also demonstrated. Overall, results indicate that in addition to enhancing inactivation of norovirus surrogates compared to higher temperatures, ultra-cold HPP performed on thawed samples especially enhances inactivation.

Efficacy of Chlorine Dioxide Gas Against Hepatitis A Virus on Blueberries, Blackberries, Raspberries, and Strawberries

Seeking a means of sanitizing berries, the effectiveness of steady state levels of gaseous chlorine dioxide (ClO₂) against hepatitis A virus (HAV) on laboratory-contaminated berries was determined. The generated ClO₂ was maintained with 1 or 2 mg/l air inside a 269-l glove box to treat 50 g batches of blueberries, raspberries, and blackberries, and 100 g batches of strawberries that were immersion coated with HAV. Normalized data for ClO₂ (ppm-h/g product) is reported as a function of ClO₂ concentration, treatment time, and weight of treated product. Treatments of ClO₂ ranging from 1.00 to 6.27 ppm-h/g berry were evaluated. When compared to untreated HAV-contaminated berries, log reductions of HAV were > 2.1 for all berry types and conditions tested indicating the gaseous ClO₂ was effective. The average log reduction with strawberries, raspberries, blueberries and blackberries treated with 1.00 ppm-h/g, the lowest ClO₂ treatment tested, were 2.44, 2.49, 3.23, and 3.45, respectively. The highest treatment of 6.27 ppm-h/g was applied at two different gas concentrations of 1 mg/l and 2 mg/l. Average log reductions for blueberries and strawberries treated with 6.27 ppm-h/g were 4.34 and 4.42, and 4.03 and 3.51, applied at 1 mg/l and 2 mg/l, respectively. For blackberries and raspberries 3.20 and 3.24, and 3.23 and 3.97 log reductions were observed for 6.27 ppm-h/g treatments applied at 1 mg/l and 2 mg/l, respectively. Results indicate that HAV contamination of berries can be substantially reduced by gaseous ClO₂ and offer industry a waterless means of sanitizing berries against HAV.

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.

Fresh Produce Safety and Quality: Chlorine Dioxide's Role

Maintaining microbial safety and quality of fresh fruits and vegetables are a global concern. Harmful microbes can contaminate fresh produce at any stage from farm to fork. Microbial contamination can affect the quality and shelf-life of fresh produce, and the consumption of contaminated food can cause foodborne illnesses. Additionally, there has been an increased emphasis on the freshness and appearance of fresh produce by modern consumers. Hence, disinfection methods that not only reduce microbial load but also preserve the quality of fresh produce are required. Chlorine dioxide (ClO₂) has emerged as a better alternative to chlorine-based disinfectants. In this review, we discuss the efficacy of gaseous and aqueous ClO₂ in inhibiting microbial growth immediately after treatment (short-term effect) versus regulating microbial growth during storage of fresh produce (long-term effect). We further elaborate upon the effects of ClO₂ application on retaining or enhancing the quality of fresh produce and discuss the current understanding of the mode of action of ClO₂ against microbes affecting fresh produce.

Strategies for Microbial Decontamination of Fresh Blueberries and Derived Products

Increasing consumption of blueberries is associated with appreciation of their organoleptic properties together with their multiple health benefits. The increasing number of outbreaks caused by pathogenic microorganisms associated with their consumption in the fresh state and the rapid spoilage of this product which is mainly caused by moulds, has led to the development and evaluation of alternatives that help mitigate this problem. This article presents different strategies ranging from chemical, physical and biological technologies to combined methods applied for microbial decontamination of fresh blueberries and derived products. Sanitizers such as peracetic acid (PAA), ozone (O3), and electrolyzed water (EOW), and physical technologies such as pulsed light (PL) and cold plasma (CP) are potential alternatives to the use of traditional chlorine. Likewise, high hydrostatic pressure (HHP) or pulsed electrical fields (PEF) successfully achieve microbial reductions in derivative products. A combination of methods at moderate intensities or levels is a promising strategy to increase microbial decontamination with a minimal impact on product quality.

Evaluation of Chlorine Dioxide Gas against Four Salmonella enterica Serovars Artificially Contaminated on Whole Blueberries

ABSTRACT

Fresh produce, such as blueberries, continues to be a source of foodborne illness in the United States. Despite new practices and intervention technologies, blueberries and other produce are contaminated with foodborne pathogens, such as Salmonella. The aim of this study was to evaluate the efficacy of chlorine dioxide gas (CDG) against Salmonella enterica serovars Newport, Stanley, Muenchen, and Anatum on artificially contaminated whole fresh blueberries. Blueberries were dip inoculated into a 400-mL bath containing a Salmonella serovar cocktail of either ca. 6 or 9 log CFU/mL. Samples were dried for either 2 or 24 h before treatment with 1.5 or 3 mg of CDG/L of air to a final treatment of 3.55 to 6 ppm/h/g of blueberry. Salmonella cells were recovered by stomaching CDG-treated and nontreated control samples with 0.1% peptone and enumerated on xylose lysine Tergitol 4 agar. CDG treatments achieved up to a 5.63-log CFU/g reduction of the cocktail using 5.5 ppm/h/g, whereas the lowest treatment, 4 ppm/h/g (1.5 mg of CDG/L), was still capable of a 4.45-log CFU/g reduction. Incubation time significantly (P < 0.001) affected CDG efficacy against both inoculation concentrations. Additionally, all serovars responded similarly to CDG treatment when tested individually (P > 0.0691). Finally, the availability of a water reservoir during treatments did not have a significant effect (P = 0.9818) on CDG efficacy in this study. Our results demonstrate that CDG can be an efficacious treatment option for whole blueberry decontamination.

HIGHLIGHTS

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.