Search Results (13)

Concerns about microplastic pollution have risen as numerous studies have reported detection of microplastics in foods, including seafood. One emerging concern is the ability of microplastics to vector pathogens that can adhere to biofilms on microplastic surfaces. Here, we investigated whether microplastics can facilitate zoonotic protozoan parasite contamination in shellfish. Oysters were selected for this study because they are commonly eaten raw and can harbor zoonotic protozoan pathogens. Acclimated live oysters were exposed in closed aquaria to Cryptosporidium, Giardia, and Toxoplasma (oo)cysts that had been incubated in seawater either as protozoa alone (P treatment) or with preconditioned polyester microfibers (P + M treatment). After overnight exposure, oysters were transferred to clean seawater flow-through aquaria for depuration. Over the experimental period, oysters exposed to both protozoa and microfibers had significantly higher numbers of protozoan pathogens than oysters exposed to protozoa alone. Our study provides experimental evidence that microplastics may facilitate protozoan pathogen contamination in shellfish. These results demonstrate how anthropogenic pollution may have unintended consequences on infectious disease transmission in coastal ecosystems, with potential risk to wildlife populations and human public health. Full article

Bivalve molluscs represent an important food source and have a significant economic impact through their commercialization in many countries. As high-capacity filter feeders, they can bioaccumulate contaminants and pathogens, creating tangible consumer health risks. This study presents the first comprehensive patent landscape of bivalve mollusc decontamination technologies indexed in international patent databases (Espacenet). The survey identified 30 patents filed between 1989 and 2025. Unlike reviews based solely on scientific literature, this work provides, for the first time, a global mapping of technological developments aimed at enhancing the safety of bivalves-derived foods. The analysis highlights depuration as the predominant technology, which continues to be refined and optimized. It also reveals the emergence of disruptive approaches—such as photodynamic sterilization, the use of probiotics, immunopotentiators, natural antimicrobial compounds, and genetic hybridization—developed to preserve the viability and sensory quality of the organisms. The novelty of this study lies in providing a technological overview of innovation within the aquaculture sector, emphasizing the transition from conventional methods to cleaner, integrated, and sustainable technologies. Furthermore, the research identifies the advancement of hybrid decontamination systems that combine microbiological efficiency, environmental preservation, and commercial value, contributing to safer and more technologically advanced shellfish production. Full article

This study assessed the presence, abundance, and characteristics of microplastics (MPs) in farmed Pacific oysters (Crassostrea gigas) and evaluated the efficacy of depuration in reducing MPs under laboratory-controlled and commercial conditions. Oysters cultivated in the Lima estuary (NW Portugal) were sampled in autumn and winter, along with adjacent surface water and sediment, to investigate potential contamination sources. MP concentrations in oysters varied temporally, with higher levels in October 2023 (0.48 ± 0.34 MPs g⁻¹ ww) than in February 2024 (0.09 ± 0.07 MPs g⁻¹ ww), while the environmental levels remained stable across dates. All MPs were fibres, predominantly transparent, followed by blue and black. Fourier-Transform Infrared Spectroscopy (FTIR) confirmed cellulose and polyethylene terephthalate (PET) as dominant polymers in oysters and environmental samples. No clear correlation was found between MPs in oysters and surrounding compartments. Laboratory depuration reduced MPs by 78% within 48 h, highlighting its potential as a mitigation strategy. However, depuration was less effective under commercial conditions, possibly due to lower initial contamination levels. These findings suggest that oysters may act as a vector for human exposure to MPs via seafood consumption. While depuration shows promise in reducing contamination, further research is needed to optimise commercial protocols and enhance the safety of aquaculture products. Full article

Marine plastic waste represents, in recent decades, a major threat to the environment, as plastics degrade into microplastics (MPs) that a wide range of organisms ingest. Filter-feeding taxa, including bivalves, serve as indicators of environmental contamination due to their ingestion of MPs. This study investigated (a) the bioaccumulation and depuration capacities of Ostrea edulis exposed to MPs and (b) the identification of reference genes for assessing stress responses in bivalves under MP exposure. The experimental protocol comprised a 28-day exposure to MPs followed by a 7-day depuration period. The mean concentration of accumulated MPs was 5.31 ± 0.86 particles/g, comprising filaments (79%), beads (19%), and fragments (2%). Depuration reduced MP concentrations by 69% after 24 h and by an additional 23% after 120 h. In conclusion, a two-day depuration period significantly reduced MPs in oysters intended for human consumption. Additionally, the molecular analysis identified EF-1α, GAPDH, and L5 as stable reference markers for MPs exposure experiments, supporting the development of a monitoring toolkit for MPs in marine environments. Full article

Arcobacter-related species are considered emerging food-borne and waterborne pathogens, with shellfish being a suggested reservoir. In a published study that investigated 204 shellfish samples and 476 isolates, the species Arcobacter butzleri (now known as Aliarcobacter butzleri) and Arcobacter molluscorum (now known as Malaciobacter molluscorum) have been isolated as the most dominant species. However, the efficiency of depuration for eliminating A. butzleri and M. molluscorum in comparison with Escherichia coli from mussels and oysters is unknown and is therefore the objective of this investigation. The shellfish depuration process was evaluated in the laboratory, in summer and winter, using mussels and oysters collected from the Ebro Delta harvesting areas after performing a natural contamination and an artificial contamination using the same conditions for both mollusk and seasons. The natural contamination was performed by exposing the shellfish to a freshwater channel that receives untreated sewage from the village of Poble Nou (PNC) and that had a salinity of 10.7–16.8‰. The artificial contamination exposed the shellfish to A. butzleri and E. coli (in one tank) and to M. molluscorum and E. coli in another tank under controlled conditions of salinity (34.5‰) and temperature (20 °C summer and 14 °C winter). When evaluating the reduction in the bacteria load (every 24 h) throughout 120 h, the naturally contaminated shellfish at the PNC showed a higher reduction than the shellfish contaminated at the laboratory, with the exception of M. molluscorum, that at 24 h could not be detected in summer, neither in mussels nor in oysters. This may be attributed to the fact that the bacteria from the PNC were less adapted to the conditions of high salinity (34.5‰) in which the depuration process was performed. Although temperature did not statistically make a difference in depuration, at 20 °C a higher elimination of all bacteria was recorded relative to 14 °C. In general, E. coli survived more in mussels than in oysters, and M. molluscorum suffered in both mollusks a higher reduction than A. butzleri. New studies are required to determine further the safety of bivalves regarding the presence of Arcobacter-related species. Full article

In this study, we evaluated the use of hydrolates, co-products of essential oil distillation, as processing aids to improve the depuration process of Pacific oysters (Crassostrea gigas) as a post-harvest method aimed at reducing the norovirus (NoV) viral load. Live oysters were kept in water to which hydrolates of Thymus serpyllum and Citrus limon at 1% were added for 24 h. The concentration of NoV was quantified using the ISO 15216-1 quantitative real-time RT-PCR method in the oyster digestive tissue both before and after the treatment. The results showed a significant reduction of 0.2 log in the NoV GII concentration after 24 h of treatment with 1% C. limon hydrolate. Conversely, treatment with T. serpyllum did not appear to reduce the concentration of NoV compared to the control. Additionally, a sensory analysis was conducted through a blind survey comparing untreated and treated oysters. No changes in the sensory and physical characteristics of the oysters were observed, except for a decrease in the marine flavour intensity, which was positively perceived by consumers. These results indicate that the addition of hydrolates of C. limon at 1% during depuration might represent a promising processing aid for enhancing both the safety and acceptability of live oysters. Full article

Recently, our in vitro study on the effects of plasma-activated simulated seawater (PASW) demonstrated its potential as a novel, alternative disinfectant in oyster depuration. In this current study, PASW’s physicochemical and antimicrobial properties were identified and its effects on oyster quality were observed. Simulated seawater (SS) activated by plasma for 10 min (PASW10) increased in temperature, oxidation reduction potential, and electrical conductivity with a decrease in those parameters after 1:1 dilution with SS (PASW10 (1:1)). The pH decreased immediately after plasma activation and subsequently increased after dilution. Nitrate and nitrite concentrations were higher in PASW10 (1:1) compared to PASW10 (3:1). No free available chlorine was detected in undiluted PASW10. Processing using SS and PASW10 (1:1) depuration and refrigeration of E. coli-bioaccumulated oysters was observed. Significantly higher reductions in total coliform and E. coli were noted for PASW10 (1:1) treated oyster samples after 24 h compared to refrigerated samples. No significant differences in values for condition index or biting force of oyster meats were observed for the processed samples after 24 h. Overall, the novel and environment-friendly PASW could be used as an alternative antimicrobial disinfectant in oyster depuration systems because it does not negatively affect an oyster’s viability or quality. Full article

As filter-feeding animals farmed in water bodies exposed to anthropogenic influences, oysters can be both useful bioremediators and high-risk foodstuffs, considering that they are typically consumed raw. Understanding the dynamic of bacterial and viral load in Pacific oyster (Crassostrea gigas) tissues, hemolymph, outer shell surface biofilm, and farming water is therefore of great importance for microbiological risk assessment. A one-year survey of oysters collected from a class B production area (Canal de Mira, on the Portuguese western coast) revealed that these bivalve mollusks have a good depurating capacity with regard to bacteria, as Salmonella spp. and viable enterococci were not detected in any oyster flesh (edible portion) samples, despite the fact that these bacteria have regularly been found in the farming waters. Furthermore, the level of Escherichia coli contamination was clearly below the legal limit in oysters reared in a class B area (>230–≤4600 MPN E. coli/100 g). On the contrary, norovirus was repeatedly detected in the digestive glands of oysters sampled in autumn, winter, and spring. However, their presence in farming waters was only detected during winter. Full article

The main purpose of this study is to study the effect of live oysters on various quality indicators after alkaline electrolytic seawater depuration. The depuration treatments were carried out for 12 h at temperatures of 5 °C, 10 °C, 15 °C, and 20 °C, pH = 9, 10, and 11, respectively. The total aerobic plate count (TAPC) of oyster meat was reduced from about 5.2 ± 0.4 log CFU/g to below detection limits when the oysters were depurated in pH = 11 alkaline electrolytic seawater for 9 h at 5 °C and 12 h at 10 °C. At the same pH value, the lower the seawater temperature, the lower the amount of TAPC, and it decreased with the increase in depuration time. After the oyster had been depurated, the chemical components contained in the oyster meat, such as protein, crude fat, and glycogen, did not change differentially. On the other hand, each group of live oysters (4 individuals) spat out an average of about 690–695 ± 0.4 mg of impurities and dirt. These are new achievements and discoveries. When the depurated oyster meat was stored at a low temperature, the freshness period could be extended to 21 days, which is much longer than the 5 days of the un-depurated oyster meat, and this is a significant difference. If coupled with vacuum packaging, the effect will be even better. Full article

This work explored the effects of salinity and temperature on the efficacy of purging V. parahaemolyticus from eastern oysters (Crassostrea virginica). Oysters were inoculated with a 5-strain cocktail of V. parahaemolyticus to levels of 10⁴ to 10⁵ MPN (most probable number)/g and depurated in a controlled re-circulating wet-storage system with artificial seawater (ASW). Both salinity and temperature remarkably affected the efficacy for the depuration of V. parahaemolyticus from oysters during wet-storage. The wet-storage process at salinity 20 ppt at 7.5 °C or 10 °C could achieve a larger than 3 log (MPN/g) reduction of Vibrio at Day 7, which meets the FDA’s requirement as a post-harvest process for V. parahaemolyticus control. At the conditions of 10 °C and 20 ppt, a pre-chilled system could achieve a 3.54 log (MPN/g) reduction of Vibrio in oysters on Day 7. There was no significant difference in the shelf life between inoculated and untreated oysters before the depuration, with a same survival rate (stored in a 4 °C cooler for 15 days) of 93%. Full article

Depuration is generally the main treatment employed for bivalve mollusks harvested from contaminated sites. Commercial depuration has demonstrated to be effective for removal of bacterial pathogens, although it probably provides only limited efficacy against human enteric viruses. We evaluated the quantitative reduction of norovirus (NoV) genogroups I and II in naturally contaminated oysters after 1, 4, and 9 days of depuration. The process was conducted in an authorized depuration plant, and NoV concentration was determined by RT-qPCR according to ISO 15216-1:2017 method. Regardless of the NoV genogroup, our results showed no significant reduction in NoV concentration after 1 day of depuration. Higher mean reduction (68%) was obtained after 4 days of treatment, while no further increase was observed after 9 days. Overall, reduction was highly variable, and none of the trials showed statistically significant reduction in NoV RNA concentration at the end of each depuration period. Indeed, NoV concentration remained high in 70% of samples even after 9 days of depuration, with values ranging between 4.0 × 10² and 2.3 × 10⁴ g.c./g. These results indicate that an extension of commercial depuration time does not appear to be effective for reducing or eliminating NoV in oysters. Full article

Microbiological contamination of bivalve molluscs is one of the major concerns inherent to food safety, thus depuration is frequently needed to assure food safety levels associated with their consumption. Salinity plays an important role in the metabolic activity of bivalves and as such can influence their depuration capacity. This study aimed to evaluate the effect of salinity (25, 30, 35 and 40) on the efficiency of the depuration process, along with the quality and shelf-life of Crassostrea gigas. For this, a 24-h depuration was carried out, followed by a storage period at 5 ± 1 °C for six days. Microbiological analyses and biochemical parameters related to oxidative stress response were analysed. Escherichia coli load was reduced in only 24 h, disregarding the salinity of the system. After the shelf-life period, the activity of the antioxidant defences at salinities 35 and 40 is higher but is still not sufficient to avoid lipid peroxidation. Over time, there is a decrease in oyster metabolism probably due to being chilled and to the action of exposure to air. In sum, this study suggests salinities between 25 and 30 as preferential for the depuration process of C. gigas and subsequent quality during shelf-life. Full article

Shellfish toxin monitoring programs often use mussels as the sentinel species to represent risk in other bivalve shellfish species. Studies have examined accumulation and depuration rates in various species, but little information is available to compare multiple species from the same harvest area. A 2-year research project was performed to validate the use of mussels as the sentinel species to represent other relevant eastern Canadian shellfish species (clams, scallops, and oysters). Samples were collected simultaneously from Deadmans Harbour, NB, and were tested for paralytic shellfish toxins (PSTs) and amnesic shellfish toxin (AST). Phytoplankton was also monitored at this site. Scallops accumulated PSTs and AST sooner, at higher concentrations, and retained toxins longer than mussels. Data from monitoring program samples in Mahone Bay, NS, are presented as a real-world validation of findings. Simultaneous sampling of mussels and scallops showed significant differences between shellfish toxin results in these species. These data suggest more consideration should be given to situations where multiple species are present, especially scallops. Full article