Arsenic-containing hydrocarbons have been identified for the first time as natural components of fish oil.
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Pseudomonas spp. is a group of microorganisms commonly found in fish and other fresh foods and is involved in their spoilage process. The aim of this study was to develop a rapid and accurate quantitative assay for Pseudomonas spp. in fish using real-time PCR. The assay targets the carbamoyl phosphate synthase gene (carA) with SYBR green based real-time PCR. The selectivity of the assay was confirmed using 24 Pseudomonas strains and 55 non-pseudomonad strains. A linear quantification was established over seven orders of magnitude, from 40 – 47 copies reaction−1. The assay was validated on cod samples collected during two shelf life trials and showed a high degree of correlation to the plate count method (rP = 0.891) where the difference between the methods was 0.04 log10CFU g−1 on average. The study shows that it is possible to quantify accurately the specific spoilage organisms belonging to the genus Pseudomonas in fish using real-time PCR. The method takes less than 5 h from sampling to results. The short detection time of the method can provide the fish industry with an important tool for quality control and processing management.
Six glycoside hydrolase (GH) family 13 members, classified under the polyspecific neopullulanase subfamily GH13_20 (also termed cyclomaltodextrinase) were analysed. They originate from thermophilic bacterial strains (Anoxybacillus flavithermus, Laceyella sacchari, and Geobacillus thermoleovorans) or from environmental DNA, collected after in situ enrichments in Icelandic hot springs. The genes were isolated following the CODEHOP consensus primer strategy, utilizing the first two of the four conserved sequence regions in GH13. The typical domain structure of GH13_20, including an N-terminal domain (classified as CBM34), the catalytic module composed of the A-and B-domains, and a C-terminal domain, was found in five of the encoded enzymes (abbreviated Amy1, 89, 92, 98 and 132). These five enzymes degraded cyclomaltodextrins (CDs) and starch, while only three, Amy92 (L. sacchari), Amy98 (A. flavithermus) and Amy132 (environmental DNA), also harboured neopullulanase activity. The L. sacchari enzyme was monomeric, but with CD as the preferred substrate, which is an unusual combination. The sixth enzyme (Amy29 from environmental DNA), was composed of the ABC-domains only. Preferred substrate for Amy29 was pullulan, which was degraded to panose, and the enzyme had no detectable activity on CDs. In addition to its different activity profile and domain composition, Amy29 also displayed a different conservation (LPKF) in the fifth conserved region (MPKL) proposed to identify the subfamily. All enzymes had apparent temperature optima in the range 50–65°C, while thermostability varied, and was highest for Amy29 with a half-life of 480 min at 80°C. Calcium dependent activity or stability was monitored in four enzymes, but could not be detected for Amy29 or 98. Tightly bound calcium can, however, not be ruled out, and putative calcium ligands were conserved in Amy98.
Development of new technologies and preservation methods to offer conveniently packed fish with sufficient keeping quality is important to meet increasing demand for value-added fresh fish products on the market. The aim of this study was to investigate the effect of combined application of modified atmosphere packaging (MAP) and superchilled storage on the shelf life of fresh cod loins. Fresh cod loins were packed in polystyrene boxes and in MA (CO2/N2/O2: 50%/45%/5%) on day 3 postcatch and stored at chilled (1.5 °C) and superchilled (−0.9 °C) temperatures. Quantitative descriptive analysis (QDA) and physical, chemical, and microbial analyses were carried out during the 21 d of storage. Superchilled storage alone compared with traditional chilled storage in polystyrene boxes increased the total shelf life (days from catch) of cod loins from 9 to 16 or 17 d. Chilled MA packaging increased the shelf life from 9 to 14 d and when MAP and superchilled storage were combined, a synergistic effect was observed and the shelf life was further extended to at least 21 d. It is noteworthy that the characteristic fresh and sweet taste can be maintained longer under such conditions. This could contribute to enhanced eating quality of fresh cod fillets for consumers in distant markets. However, MAP combined with superchilled storage resulted in different textural properties. Superchilled MA packed cod loins had more meaty texture compared to other sample groups after 7-d storage.
The effect of salinity on growth, feed conversion efficiency and blood physiology was investigated by rearing Atlantic halibut Hippoglossus hippoglossus (initial weight 25.5 ± 0.8 g, mean ± SEM) at salinities of 15, 25 or 32‰ for 4 months at 12 °C. The final mean weight of the fish reared at 15‰ (135.9 ± 5.1) and 25‰ (130.8 ± 5.1) was significantly larger than that of fish reared at 32‰ (107.6 ± 5.2). Similarly, the specific growth rates (SGR) and feed conversion efficiency (FCE) were significantly higher at both 15‰ (SGR: 1.29 ± 0.03; FCE: 1.21 ± 0.04) and 25‰ (SGR: 1.25 ± 0.04; FCE: 1.18 ± 0.06) compared to 32‰ (SGR: 1.16 ± 0.04; FCE: 0.97 ± 0.10). Of the osmoregulatory and metabolic parameters analysed in plasma Na+ and glucose were significantly lower in fish reared at 15‰ compared to both 25‰ and 32‰. The acid–base balance was influenced by the salinity treatment as there was a general trend towards higher pH, pCO2 and HCO3− in the full salinity group compared to the 15‰ group. The results clearly show that the optimum conditions for farming Atlantic halibut, both with respect to growth rate and feed conversion, is at salinities lower than 32‰. This is an important finding for the halibut industry.
Polyfluorinated alkyl compounds (PFCs) are a group of chemicals of growing concern that have been detected in biological and abiotic samples worldwide. This study reports the concentrations of a suite of PFCs: perfluorooctyl sulfonate (PFOS), perfluorooctyl sulfonamide (PFOSA) and perfluorinated carboxylic acids (PFCAs) in guillemot (Uria aalge) eggs, collected in North-Western Europe, from Iceland, the Faroe Islands, Sweden and two locations in Norway. The highest concentrations of PFOS were found in samples from Sweden (mean 400 ng g−1 wet weight (w.w.)), which were almost five times higher than concentrations found in Norwegian samples (mean 85 ng g−1 w.w. from both sample sites). The concentrations found in Icelandic and Faroe samples were lowest (mean 16 and 15 ng g−1 w.w., respectively). Only Swedish samples differed significantly from the other locations. In general, PFCAs show a different spatial trend than PFOS. Perfluorooctanoic acid (PFOA) was not detected in any sample and perfluorononanoic acid (PFNA) was only detected in samples from Sweden. The most abundant PFCA was perfluoroundecanoic acid (PFUA) with highest concentrations in samples from Sweden (mean 82 ng g−1 w.w.), samples from the Faroe Islands had the second highest concentration (mean 57 ng g−1 w.w.) and samples from Iceland and Norway had concentrations ranging between 18 and 30 ng g−1 w.w. The original hypothesis was based on the idea that PFC concentrations are the highest close to more densely populated and industrialized areas and lower levels in remote areas. However, the geographic pattern is more complicated than predicted and varies among different PFCs.
Changes in the conformation of catfish (Ictalurus punctatus) myosin due to (i) cations (ii) alkaline pH and (iii) salt addition were determined using circular dichroism, tryptophan fluorescence, differential scanning calorimetry and hydrophobicity studies. The relation between conformation and storage modulus (G′) of alkali treated myosin was studied. Two types of bases, NaOH and KOH were used for unfolding myosin under three alkaline conditions, pH 11.0, 11.5 and 12.0. Myosin, unfolded under alkali conditions was immediately refolded by adjusting pH back to 7.3. Subjecting myosin to alkaline conditions and subsequent readjustment to pH 7.3 increased the G′ of thermally treated myosin. G′ was affected by the presence or absence of salt during alkali treatments. When salt was present during alkali unfolding of myosin, the added salt stabilized the conformation of myosin against alkali unfolding and denaturation. In the absence of salt or when salt was added after refolding, myosin showed significantly higher denaturation and high G′ on heating and cooling. Among the different alkaline pH values, myosin treated at pH 11.0 showed higher G′. The type of anions influenced the conformation of myosin and the strength of gels. Treatment of myosin with KOH resulted in greater denaturation and higher gelling ability (G′) compared to NaOH.
Simulated recalls of fish products sampled in retailer shops were conducted in five Nordic countries to indicate the effectiveness and accuracy of chain traceability systems. The results suggested poor traceability practices at the vessels/auctions and revealed that batch sizes at the last traceable step of the raw material vary considerably. However, the existing traceable information seemed to be easily accessible. Altogether, the fish industry in the Nordic countries seems not to be fully prepared for a recall. Improved traceability awareness and practices in the whole chain can limit the batch sizes and minimize costs in case of a real recall.
To examine whether there is a relationship between the degree of Campylobacter contamination observed in product lots of retail Icelandic broiler chicken carcasses and the incidence of human disease, 1,617 isolates from 327 individual product lots were genetically matched (using the flaA short variable region [SVR[) to 289 isolates from cases of human campylobacteriosis whose onset was within approximately 2 weeks from the date of processing. When there was genetic identity between broiler isolates and human isolates within the appropriate time frame, a retail product lot was classified as implicated in human disease. According to the results of this analysis, there were multiple clusters of human disease linked to the same process lot or lots. Implicated and nonimplicated retail product lots were compared for four lot descriptors: lot size, prevalence, mean contamination, and maximum contamination (as characterized by direct rinse plating). For retail product distributed fresh, Mann-Whitney U tests showed that implicated product lots had significantly (P = 0.0055) higher mean contamination than nonimplicated lots. The corresponding median values were 3.56 log CFU/carcass for implicated lots and 2.72 log CFU/carcass for nonimplicated lots. For frozen retail product, implicated lots were significantly (P = 0.0281) larger than nonimplicated lots. When the time frame was removed, retail product lots containing Campylobacter flaA SVR genotypes also seen in human disease had significantly higher mean and maximum contamination numbers than lots containing no genotypes seen in human disease for both fresh and frozen product. Our results suggest that cases of broiler-borne campylobacteriosis may occur in clusters and that the differences in mean contamination levels may provide a basis for regulatory action that is more specific than a presence-absence standard.
Regular seafood consumption is associated with beneficial health effects. This book reviews the research on seafood and health, the use and quality aspects of marine lipids and seafood proteins as ingredients in functional foods and consumer acceptance of (marine) functional food. The first chapter covers novel merging areas where seafood may prevent disease and improve health such as in cognitive development, mental health, cancer, allergy and oxidative stress are highlighted. Cases where nutrients in seafood may have health protective effects such as in proteins, peptides, amino acids, selenium, chitosan, glucosamine and chondroitin sulphate are also discussed. The next chapters cover quality aspects of marine lipids and seafood proteins as ingredients in functional foods. Lipids and proteins must have and retain a high quality so that the sensory and functional properties and the shelf life of the final product are acceptable. The methods used for processing marine lipids and proteins, are discussed as well as the different factors that can affect their quality in functional foods. The book then concentrates on factors related to consumers’ attitudes, knowledge and awareness of functional foods. There are variations in types of carrier products and of demographic and cross-cultural factors in acceptance of functional foods. Finally, the book discusses challenges for small and medium enterprises to commercialise healthy nutrition. Variations in characteristics, capabilities, challenges and opportunities in the marketplace are presented using a Nordic study as reference.