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.

Innovative Seafood Preservation Technologies: Recent Developments

Fish and fishery products are among the food commodities of high commercial value, high-quality protein content, vitamins, minerals and unsaturated fatty acids, which are beneficial to health. However, seafood products are highly perishable and thus require proper processing to maintain their quality and safety. On the other hand, consumers, nowadays, demand fresh or fresh-like, minimally processed fishery products that do not alter their natural quality attributes. The present article reviews the results of studies published over the last 15 years in the literature on: (i) the main spoilage mechanisms of seafood including contamination with pathogens and (ii) innovative processing technologies applied for the preservation and shelf life extension of seafood products. These primarily include: high hydrostatic pressure, natural preservatives, ozonation, irradiation, pulse light technology and retort pouch processing.

Listeria monocytogenes in Vacuum-Packed Smoked Fish Products: Occurrence, Routes of Contamination, and Potential Intervention Measures

The occurrence of Listeria monocytogenes in ready-to-eat (RTE) fish products is well documented and represents an important food safety concern. Contamination of this pathogen in vacuum-packed (VP) smoked fish products at levels greater than the RTE food limit (100 CFU/g) has been traced to factors such as poor sanitary practices, contaminated processing environments, and temperature abuse during prolonged storage in retail outlets. Intervention technologies including physical, biological, and chemical techniques have been studied to control transmission of L. monocytogenes to these products. High-pressure processing, irradiation, and pulsed UV-light treatment have shown promising results. Potential antilisterial effects of some sanitizers and combined chemical preservatives have also been demonstrated. Moreover, the concept of biopreservation, use of bioactive packaging, and a combination of different intervention technologies, as in the hurdle concept, are also under consideration. In this review, the prevalence, routes of contamination, and potential intervention technologies to control transmission of L. monocytogenes in VP smoked fish products are discussed.

Controlling Vibrio vulnificus and spoilage bacteria in fresh shucked oysters using natural antimicrobials

This study evaluated the efficacy of grape seed extract (GE), citric acid (CA) and lactic acid (LA) on the inactivation of Vibrio vulnificus and inherent microflora in fresh shucked oysters. The minimum inhibitory concentration (MIC) of GE, CA or LA against V. vulnificus was determined. Furthermore, the shucked oysters were artificially inoculated with V. vulnificus. The inoculated shucked oysters (25 g) were then dipped in 250 ml GE, CA or LA solutions for 10 min. The population of V. vulnificus in shucked oysters was determined. The effects of the treatments with GE, CA or LA solutions on the inherent microbiota in fresh shucked oysters during storage at 5°C for 20 days were also studied. The MICs of GE, CA or LA against V. vulnificus were 10.0, 5.0 or 1.0 mg ml(-1), respectively. The concentrations of 500, 300 or 150 mg ml(-1) GE, CA or LA solutions were needed to reduce the population of V. vulnificus to below the detection level (1.0 log g(-1)). Treatment with 500, 300, 150 mg ml(-1) GE, CA or LA significantly reduced the initial inherent microbiota in fresh shucked oysters, and inherent levels were significantly (P < 0.05) lower than the control sample throughout refrigerated storage for 20 days.

SIGNIFICANCE AND IMPACT OF THE STUDY

Oysters filter large volume of seawater during their feeding activities that concentrate bacteria such as Vibrio vulnificus in their body. The presence of V. vulnificus in oysters has a serious impact on public health and international trade. There is increasing concern over the use of chemical preservatives. Furthermore, the food industry is looking for new natural preservation methods. This study indicated that lactic acid and citric acid wash solutions could offer an inexpensive, natural and strong approach to control V. vulnificus and spoilage bacteria in fresh shucked for the oyster industry.

Control of Listeria monocytogenes and spoilage bacteria on smoked salmon during storage at 5 °C after X-ray irradiation

In this study, smoked salmon fillets were artificially inoculated with Listeria monocytogenes (3.7 ± 0.2 log CFU g(-1)) and treated with X-ray irradiation generated by a RS 2400 X-ray machine (Rad Source Technologies Inc.) using doses of 0.0, 0.1, 0.5, 1.0, and 2.0 kGy. Unirradiated and irradiated samples were then stored at 5 °C for 35 days and tested for L. monocytogenes count after 0, 5, 10, 15, 20, 25, 30, and 35 days. Also, uninoculated-untreated and uninoculated-treated samples with the lowest and highest X-ray doses (0.1 and 2.0 kGy) were stored at 5 °C and examined for psychrotrophs and mesophiles counts after 0, 5, 10, 15, 20, 25, 30, and 35 days. The initial L. monocytogenes population (3.7 log CFU g(-1) ) was significantly (p < 0.05) reduced to an undetectable level (<1.0 log CFU g(-1)) by treatment with 1.0 kGy X-ray. Treatment with 0.1 kGy X-ray significantly reduced the initial psychrotrophs and mesophiles counts from 5.3 and 3.0 to 3.3 and 2.3, respectively. However, L. monocytogenes, psychrotrophs and mesophiles counts were gradually increased during storage. Treatment with 2.0 kGy X-ray kept the L. monocytogenes population under detectable level until 35 days. Treatment with 2.0 kGy X-ray kept the mesophiles and psychrotrophs counts within the acceptable level until 35 days. These results revealed that treatment with X-ray irradiation can significantly reduce the risk of listeriosis and extend the shelf life of smoked salmon during storage at 5 °C.

Impact of irradiation on fish and seafood shelf life: a comprehensive review of applications and irradiation detection

Irradiation is one of the most important and effective methods towards food preservation despite the consumer lack of trust and aversion towards this method. Irradiation effectiveness greatly depends on the dose provided to food. This review aims at summarizing all available information regarding the impact of irradiation dose on the shelf life and microflora and sensory and physical properties of fish, shellfish, molluscs, and crustaceans. The synergistic effect of irradiation in conjunction with other techniques such as salting, smoking, freezing, and vacuum packaging was also reported. Another issue covered within the frame of this review is the detection (comparison of methods in terms of their effectiveness and validity) of irradiated fish and seafood. The information related to fish and seafood irradiation and its detection is presented by means of 11 comprehensive tables and 9 figures.