Basis for a new procedure to eliminate diarrheic shellfish toxins from a contaminated matrix

Okadaic Acid Detection through a Rapid and Sensitive Amplified Luminescent Proximity Homogeneous Assay

Okadaic acid (OA), a marine biotoxin produced by microalgae, poses a significant threat to mariculture, seafood safety, and human health. The establishment of a novel, highly sensitive detection method for OA would have significant practical and scientific implications. Therefore, the purpose of this study was to develop an innovative approach for OA detection. A competitive amplified luminescent proximity homogeneous assay (AlphaLISA) was developed using the principle of specific antigen-antibody binding based on the energy transfer between chemiluminescent microspheres. The method was non-washable, sensitive, and rapid, which could detect 2 × 10-2-200 ng/mL of OA within 15 min, and the detection limit was 4.55 × 10-3 ng/mL. The average intra- and inter-assay coefficients of variation were 2.54% and 6.26%, respectively. Detection of the actual sample results exhibited a good correlation with high-performance liquid chromatography. In conclusion, a simple, rapid, sensitive, and accurate AlphaLISA method was established for detecting OA and is expected to significantly contribute to marine biotoxin research.

Complementary Methods to Improve the Depuration of Bivalves: A Review

Bivalves are filter feeders that can accumulate and concentrate waterborne contaminants present in the water in which they live. Biotoxins, pathogenic bacteria, viruses, and heavy metals present in the aquaculture environment constitute the main hazards for human health. The most common method employed for combating waterborne pollutants in bivalves is depuration with purified seawater. Although this method is effective at increasing the microbiological quality of bivalves, in most cases, it is ineffective at eliminating other risks, such as, for example, viruses or heavy metals. Biological (bacteriocins and bacteriophages), physical (UV light, ozone, and gamma-irradiation), chemical (metallothioneins and chitosan), and other industrial processing methods have been found to be useful for eliminating some contaminants from seawater. The aim of this work was to provide a review of academic articles concerning the use of treatments complementary to conventional depuration, aiming to improve depuration process efficiency by reducing depuration times and decreasing the levels of the most difficult-to-erase contaminants. We conclude that there are different lab-tested strategies that can reduce depuration times and increase the food safety of bivalve produce, with possible short- and long-term industrial applications that could improve the competitivity of the aquaculture industry.

Evaluation of the Impact of Mild Steaming and Heat Treatment on the Concentration of Okadaic Acid, Dinophysistoxin-2 and Dinophysistoxin-3 in Mussels

This study explores the effect of laboratory and industrial steaming on mussels with toxin concentrations above and below the legal limit. We used mild conditions for steaming, 100 °C for 5 min in industrial processing, and up to 20 min in small-scale laboratory steaming. Also, we studied the effect of heat on the toxin concentration of mussels obtained from two different locations and the effect of heat on the levels of dinophysistoxins 3 (DTX3) in both the mussel matrix and in pure form (7-O-palmitoyl okadaic ester and 7-O-palmytoleyl okadaic ester). The results show that the loss of water due to steaming was very small with a maximum of 9.5%, that the toxin content remained unchanged with no concentration effect or increase in toxicity, and that dinophysistoxins 3 was hydrolyzed or degraded to a certain extent under heat treatment. The use of liquid-certified matrix showed a 55% decrease of dinophysistoxins 3 after 10 min steaming, and a 50% reduction in total toxicity after treatment with an autoclave (121 °C for 20 min).

Screening tests for the rapid detection of diarrhetic shellfish toxins in Washington State

The illness of three people due to diarrhetic shellfish poisoning (DSP) following their ingestion of recreationally harvested mussels from Sequim Bay State Park in the summer of 2011, resulted in intensified monitoring for diarrhetic shellfish toxins (DSTs) in Washington State. Rapid testing at remote sites was proposed as a means to provide early warning of DST events in order to protect human health and allow growers to test “pre-harvest” shellfish samples, thereby preventing harvest of toxic product that would later be destroyed or recalled. Tissue homogenates from several shellfish species collected from two sites in Sequim Bay, WA in the summer 2012, as well as other sites throughout Puget Sound, were analyzed using three rapid screening methods: a lateral flow antibody-based test strip (Jellett Rapid Test), an enzyme-linked immunosorbent assay (ELISA) and a protein phosphatase 2A inhibition assay (PP2A). The results were compared to the standard regulatory method of liquid chromatography coupled with tandem mass spectroscopy (LC-MS/MS). The Jellett Rapid Test for DSP gave an unacceptable number of false negatives due to incomplete extraction of DSTs using the manufacturer’s recommended method while the ELISA antibody had low cross-reactivity with dinophysistoxin-1, the major toxin isomer in shellfish from the region. The PP2A test showed the greatest promise as a screening tool for Washington State shellfish harvesters.

Effect of ozonation and γ-irradiation on post-harvest decontamination of mussels (Mytillus galloprovincialis) containing diarrhetic shellfish toxins

Contamination of shellfish with diarrhetic shellfish poisoning (DSP) toxins readily occurs during algal blooms. Such phenomena raise important public health concerns and thus comprise a constant challenge to shellfish farmers, the seafood industry and health services, considering the increasing occurrence of toxic episodes around the world. To avoid the detrimental effects of such episodes, research has focused on the use of various detoxification methodologies that should be rapid, efficient, easy to apply, and will not alter the quality and sensory properties of shellfish. In the present study, both ozonation (15 mg kg(-1) for 6 h) and γ-irradiation (6 kGy) were utilised in order to reduce the toxin content of contaminated shucked mussels, collected during the DSP episodes of 2007 and 2009 in Greece. DSP toxicity was monitored using the mouse bioassay (MBA) whilst the determination of toxin content of the okadaic acid (OA) group (both free and esterified forms) was carried out by LC/MS/MS analysis. Toxin reduction using γ-irradiation was in the range of 12-36%, 8-53% and 10-41% for free OA, OA esters and total OA, respectively. The appearance and texture of irradiated mussels deteriorated, pointing to a low potential for commercial use of this method. Ozonation of mussels resulted in toxin reduction in the range of 6-100%, 25-83% and 21-66% for free OA, OA esters and total OA, respectively. Reduction of OA content was substantially higher in homogenised mussel tissue compared with that of whole shucked mussels. In addition, differences detected with regard to quality parameters (TBA, sensory attributes) between ozonated and control mussels were not considerable. Even though varying percentage reductions in OA and its derivatives were achieved using ozonation under specific experimental conditions tested, it is postulated that upon optimisation ozonation may have the potential for post-harvest commercial DSP detoxification of shucked mussels.

Supercritical Fluid Pasteurization and Food Safety

Supercritical fluid pasteurization has been studied for over 20 years and the state of science and technology is such that it is now a viable and economical alternative to thermal pasteurization for a number of food products. The manufacture and distribution of food faces increasingly strict demands in terms of both safety and quality. Traditional thermal pasteurization is both effective and well-accepted by the public for milk and other products. However, thermal treatment is less effective and sometimes infeasible for certain products, such as fruit juices, seafoods and fresh vegetables. This is particularly true when the food products are packaged and shipped long distances. Supercritical fluid technology, a non-thermal, low temperature process, has been shown to reduce the viability of a number of pathogenic organisms important to the food industry. In addition, supercritical fluids, particularly CO2, have promise in deactivating subcellular pathogens such as prions and viruses. Numerous basic science investigations reveal the mechanism of supercritical fluid pasteurization and how it differs from thermal methods. Several commercial companies have issued patents and built demonstration plants based on the technology. In addition, certain supercritical fluids may provide additional benefits for food processors. This chapter provides a comprehensive review of both science and technology of supercritical fluid technology as applied to foods.

Decrease of marine toxin content in bivalves by industrial processes

Harmful algal blooms cause important economical losses due to the accumulation of toxins in shellfish. Natural detoxification occurs but this mechanism is very slow in most cases. The achievement of a method for the rapid detoxification of commercial bivalves would be very interesting for the shellfish harvesting sector in order to diminish economical losses due to harvesting areas closure. In this work, four different methods easily applicable in the food industry (freezing, evisceration, ozonization and thermal processing) were studied to gain the detoxification of four species of bivalves (mussels, scallops, clams and cockles) contaminated with the three main types of toxins (ASP, DSP, PSP). Results show that for ASP a significant decrease of the toxin levels below the legal limit (20 microg/g) is achieved by using hepatopancreas ablation or combination of simple steps (evisceration and/or thermal processing/and or freezing). In our hands, PSP toxin levels are sharply decreased under the limit of detection (35 microg STX eq/100g) after a thermal processing, inducing percentages of detoxification higher than 50%. The effect of freezing on the levels of PSP is very dependent on the matrix studied. DSP toxins are not significantly reduced with none of these methods.

Removal of lipids and diarrhetic shellfish poisoning toxins from blue mussels (Mytilus edulis) during acid and alkaline isolation of proteins

Diarrhetic shellfish poisoning (DSP) toxins pose a serious health risk for consumers of bivalves and other shellfish, as well as a huge economic burden for the bivalve-producing farmers. In this work, the aim was to utilize a solubilization-based protein-isolation method to produce a low-DSP toxin protein isolate from toxic blue mussels that are unsuitable for the whole shellfish market. A homogenate of whole mussel meat was solubilized at low pH (2.8) or high pH (11.1), followed by centrifugation and reprecipitation of the solubilized mussel proteins at the isoelectric pH. In a second centrifugation, precipitated proteins were collected. These processes resulted in 81 (acid solubilization) and 72% (alkaline solubilization) reduction in the initial DTX-1 toxin content of the mussel meat. No other DSP toxins were found in the protein isolates. Acid processing of mussel meat resulted in 50% reduction in the total lipid content, while alkaline treatment did not significantly affect the lipid content. The effect of citric acid and calcium chloride addition to the mussel meat-water homogenate on lipid and toxin content was also investigated. A poor correlation factor was surprisingly obtained between reductions in DTX-1 toxin and lipids in protein isolates from processed toxic mussels. Results from an analytical mass balance of the DTX-1 toxin during acid processing showed that 61% of this toxin ended up in the aqueous supernatant after the second centrifugation. The present study presents a promising alternative way of utilizing mussels for food production in periods when they are toxic.