Trace metals in the marine bivalve Macoma balthica in the westerschelde estuary, The Nertherlands. Part 3: Variability of the role of cytosol in metal uptake by the clams

Tellinid clams Macoma balthica were sampled every 2 months for 2.5 years at two locations from the Westerschelde estuary (The Netherlands) and submitted to in vitro short-term exposure to Cd, Cu and Zn. Total and heat-stable cytosolic metal concentrations have been measured before and after exposure to study the effects of the sampling season on metal uptake by the bivalve. We observed much higher uptakes of Cd and, to a lesser extent, Cu in winter than in summer, while Zn appears to be constantly regulated. These phenomena are amplified in the cytosol, especially for Cd, a non-essential element, for which the concentrations after exposure can reach 35–45 μg·g⁻¹ (dry wt.) in winter, but only a maximum of 0.5 μg·g⁻¹ in summer, all natural values being between 0.01 and 0.1 μg·g⁻¹ on average. The contents (μg) of the various elements, either at the total or at the cytosolic level, are not constant, hence showing that the seasonal body weight fluctuation of the clams (dilution or concentration effect) is not the only parameter responsible for the metal uptake variability. Furthermore, we have shown that the proportion of cytosolic metal is not constant, but increases with the absolute cytosolic concentration up to 35–40. Therefore, the cytosolic phase of the cells plays a growing role in Cd, Cu and Zn storage as long as their total concentration increases.     

A Striking Parallel Between Cardiolipin Fatty Acid Composition and Phylogenetic Belonging in Marine Bivalves: A Possible Adaptative Evolution?

Thirty-five species of marine mollusk bivalves were analyzed for their fatty acid (FA) composition of cardiolipin (Ptd(2)Gro). All species showed a Ptd(2)Gro with strong selectivity for only a few polyunsaturated fatty acids, but three characteristic FA profiles emerged, with clear parallels to bivalve phylogeny. A first group of 12 species belonging to the Eupteriomorphia subgroup (Filibranchia) was characterized by a Ptd(2)Gro almost exclusively composed of 22:6n-3, whereas in the four Filibranchia Pteriomorph species analyzed, this FA was combined with substantial proportions of 18:2n-6 and 18:3n-3. Finally, a third group of 20 species, all belonging to the Heterodonta subclass, possessed Ptd(2)Gro containing predominantly both 22:6n-3 and 20:5n-3. Polyunsaturated FA moieties and arrangements in the Ptd(2)Gro of some marine species investigated in other classes of the mollusk phylum (Gastropoda, Polyplacophora) were found to be different. The present results suggest that the specific Ptd(2)Gro FA compositions in bivalves are likely to be controlled and conserved in species of the same phylogenetic group. Functional significances of the evolution of this mitochondrial lipid structure in bivalves are discussed.     

免疫亲和柱净化-高效液相色谱-三重四极杆质谱法测定双壳类水产中软骨藻酸

目的 采用免疫亲和柱净化双壳类水产中的软骨藻酸,建立高效液相色谱-三重四级杆质谱串联（LC-MS/MS）方法检测双壳类水产中的软骨藻酸,为水产品中的软骨毒素检测提供方法依据。方法 选用InfinityLab Poroshell 120 EC-C18色谱柱,以10 mmol/L甲酸铵-0.1%甲酸-甲醇为流动相,采用梯度洗脱进行分离。样品用80%甲醇水提取,上清液加入PBS缓冲液后经免疫亲和柱净化,将洗脱液氮吹至干定容后上机测定。多重态反应监测（MRM）方式检测。结果 软骨藻酸的线性范围为20.0~200 ng/ml,检出限为0.002 μg/g,回收率在75.2% ~ 85.7%之间。结论 本方法特异性强、提取效果好、无基质抑制效应,适用于双壳类水产中软骨藻酸的痕量检测。     

Portuguese consumers' attitudes and perceptions of bivalve molluscs

Bivalves have been promoted as healthy food in many countries. Yet, little information is available about bivalve consumers' purchasing behaviour and attitudes. The aim of this study was to investigate the marketing and quality aspects of several bivalve species with economical value in Portugal and to examine the relationship between each respondent's demographic and socio-economic status with bivalve consumption attitudes and preferences. A randomly selected sample of 1778 people answered a web-based questionnaire. The majority of respondents claimed to consume clams (pullet carpet shell clam and Japanese carpet shell clam) and usually prefer bivalves from national production. Smell, size and cleaned shells were considered as the most important criteria when choosing live bivalves. Most consumers buy clams in supermarkets and revealed good knowledge about the risks associated with its consumption. Trust in the selling establishment and product's label information was the main perceived quality criteria associated to bivalve purchasing. Nonetheless, consumers' attitudes and preferences differed considerably according to their demographic and socio-economic characteristics. The current findings provide a useful tool for producers and stakeholders involved in the trade chain of bivalves to understand the consumption profile and the most important quality criteria involved in bivalve purchase. Additionally, it is an important tool to predict the risks of bivalve consumption as well as to understand the different scenarios of contamination occurring in harvesting areas by national competent authorities.     

高效液相色谱-串联质谱法测定双壳类水产品麻痹性贝类毒素

目的采用Supelco ENVI-Carb柱净化双壳类水产品中的麻痹性贝类毒素(PSP),建立高效液相色谱-串联质谱(HPLC-MS/MS)法检测双壳类水产品中的PSP,为水产品中的PSP检测提供方法依据。方法选用色谱柱TSK-GEL Amide-80(2.0 mm×250 mm,5μm),以2 mmol/L甲酸铵-50 mmol/L甲酸水和95%乙腈水(含2 mmol/L甲酸铵-50 mmol/L甲酸)为流动相,采用梯度洗脱进行分离。样品用1%乙酸溶液进行提取,上清液加入氨水后(pH=4.0)经Supelco ENVI-Carb柱净化,将洗脱液抽干收集,上机测定。多重反应监测(MRM)模式检测。结果PSP的线性范围为8.1~705.0μg/kg,检出限为10~35μg/kg,回收率在47.0%~91.3%之间。结论本方法提取效果好、基质效应小,适用于双壳类水产品中麻痹性贝类毒素的痕量检测。     

Improved microbial and sensory quality of clams (Venerupis rhomboideus), oysters (Ostrea edulis) and mussels (Mytilus galloprovincialis) by refrigeration in a slurry ice packaging system

The aim of this work was to evaluate a slurry ice (SI) packaging system on three bivalve species: clams (Venerupis rhomboideus), oysters (Ostrea edulis) and mussels (Mytilus galloprovincialis). Comparative analyses were performed on specimens caught in autumn and spring and compared to batches stored in conventional flake ice. Microbiological analysis of autumn specimens stored in SI showed significantly (P < 0.05) reduced numbers of mesophiles and psychrotrophs in all three species, as well as fewer Enterobacteriaceae in clams and oysters. Spring specimens also exhibited significantly (P < 0.05) lower microbial loads, with SI storage significantly (P < 0.05) improving the control of mesophiles, psychrotrophs and proteolytic bacteria in clams and oysters. Sensory analysis correlated well with microbial analyses, with a significantly (P < 0.05) better quality in terms of odour, taste, juiciness, appearance and shelf life. The SI packaging system evaluated in this work proved to be a valuable method for maintaining quality of these bivalve species.     

Fatty acid dynamics of the adductor muscle of live cockles (Cerastoderma edule) during their shelf-life and its relevance for traceability of geographic origin

Cockles (Cerastoderma edule) are commercially important bivalves that support several fisheries in European waters. The fatty acid (FA) profile of the adductor muscle (AM) of freshly collected live cockles can be used to reliably confirm their geographic origin. This approach is paramount for traceability, expose fraud and ensure food safety. However, no study has ever addressed if the FA profile of the AM of live cockles remains stable during shelf-life, as significant shifts may blur FA signatures recorded at harvest. The present study investigated the FA dynamics of the AM of live cockles during their shelf-life (seven days post-harvest under a refrigerated environment). Fatty acid methyl esters were obtained after transesterification of lipid extracts and analyzed through gas chromatography–mass spectrometry (GC–MS). Results indicated that FA profiles remained stable until the third day post-harvest. After this period cockles started to exhibit contrasting FA profiles on their AM, namely a higher percentage of heptadecanoic acid (17:0). This FA is associated with the growth of pathogenic microorganisms responsible for food spoilage. In this way, the FA profile of the AM of live cockles can be used to reliably trace geographic origin up to three days post-harvest, as long as specimens are stored under refrigerated conditions during shelf-life.