Flokkur: Greinar

Aims

To study the succession of cultivated and uncultivated microbes during the traditional curing process of skate.

Methods and Results

The microbial diversity was evaluated by sequencing 16Sr RNA clone libraries and cultivation in variety of media from skate samples taken periodically during a 9-day curing process. A pH shift was observed (pH 6·64–9·27) with increasing trimethylamine (2·6 up to 75·6 mg N per 100 g) and total volatile nitrogen (TVN) (from 58·5 to 705·8 mg N per 100 g) but with relatively slow bacterial growth. Uncured skate was dominated by Oceanisphaera and Pseudoalteromonas genera but was substituted after curing by Photobacterium and Aliivibrio in the flesh and Pseudomonas on the skin. Almost 50% of the clone library is derived from putative undiscovered species. Cultivation and enrichment strategies resulted in isolation of putatively new species belonging to the genera Idiomarina, Rheinheimera, Oceanisphaera, Providencia and Pseudomonas. The most abundant genera able to hydrolyse urea to ammonia were Oceanisphaera, Psychrobacter, Pseudoalteromonas and isolates within the Pseudomonas genus.

Conclusions

The curing process of skate is controlled and achieved by a dynamic bacterial community where the key players belong to Oceanisphaera, Pseudoalteromonas, Photobacterium, Aliivibrio and Pseudomonas.

Significance and Impact of the Study

For the first time, the bacterial population developments in the curing process of skate are presented and demonstrate a reservoir of many yet undiscovered bacterial species.

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A process for the effective extraction and fractionation of phlorotannins from Fucus vesiculosus with high antioxidant potentials was investigated. The antioxidant activity of F. vesiculosus extract/fractions was assessed by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, reducing power, and ferrous ion-chelating assays. Among the crude extract and different polarity fractions, the phlorotannin-enriched ethyl acetate fraction possessed the highest DPPH scavenging activity and reducing power. This fraction was further fractionated by Sephadex LH-20 column chromatography or ultrafiltration. The antioxidant properties were evaluated by both the above chemical antioxidant tests and a mononuclear cell-based bioassay. Sephadex subfractions LH-2 and LH-3 with high total phlorotannin content exhibited strong DPPH quenching activity, comparable to those of ascorbic acid and butylated hydroxytoluene and significantly higher than that of α-tocopherol. Polyphenols in F. vesiculosus were found to consist mainly of high molecular weight phlorotannin polymers. There were no clear relationships between the degree of polymerization, molecular size, and antioxidant activity. All the subfractions separated by Sephadex LH-20 column chromatography and ultrafiltration showed a high ability to scavenge reactive oxygen species generated by mononuclear cells. Further characterization of the phlorotannin compounds was performed on six Sephadex subfractions. Several phlorotannin oligomers were tentatively identified on the basis of HPLC–ESI-MSⁿ analyses.

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The global market for seafood products continues to increase year by year. Food safety considerations are as crucial as ever in this sector, and higher standards of quality are demanded even as products are shipped greater distances around the world. The current global focus on the connection between diet and health drives growth in the industry and offers commercial opportunities on a number of fronts. There is great interest in the beneficial effects of marine functional compounds such as omega-3 polyunsaturated fatty acids. Seafoods are well-known as low calorie foods, and research continues into the nutritional effects on, for example, obesity and heart disease. In addition, by-products of marine food processing can be used in nutraceutical applications.

This book is a resource for those interested in the latest advances in the science and technology of seafood quality and safety as well as new developments in the nutritional effects and applications of marine foods. It includes chapters on the practical evaluation of seafood quality; novel approaches in preservation techniques; flavour chemistry and analysis; textural quality and measurement; packaging; the control of food-borne pathogens and seafood toxins. New research on the health-related aspects of marine food intake are covered, as well as the use of seafoods as sources of bioactives and nutraceuticals. The book is directed at scientists and technologists in academia, government laboratories and the seafood industries, including quality managers, processors and sensory scientists.

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Thermococcus barophilus is a hyperthermophilic, anaerobic, mixed heterotrophic, and carboxydotrophic euryarchaeon isolated from the deep sea hydrothermal vent Snakepit site on the mid-Atlantic ridge at a depth of 3,550 m. T. barophilus is the first true piezophilic, hyperthermophilic archaeon isolated, having an optimal growth at 40 MPa. Here we report the complete genome sequence of strain MP, the type strain of T. barophilus. The genome data reveal a close proximity with Thermococcus sibiricus, another Thermococcus isolated from the deep biosphere and a possible connection to life in the depths.

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Low field Nuclear Magnetic Resonance was used to evaluate the effect of salt and modified atmosphere packaging (MAP) on cod loins during superchilled storage. Transversal and longitudinal proton relaxation times of the cod loins were measured with Carr–Purcell–Meiboom–Gill (CPMG) and Inversion Recovery (IR) pulse sequences respectively. The relaxation parameters reflected the observed differences in the muscle caused by variation in salt concentration, the choice of salting method (brining or brine injection) and packaging (air or MAP), as well as superchilled storage temperature and storage time. Significant correlations were found between the NMR parameters and parameters describing the water dynamics of the muscle (moisture and salt content, water holding capacity, drip and cooking yield), as well as muscle pH and counts of H₂S-producing bacteria in chosen sample groups. The study showed the possibility of using low field NMR to indicate fish quality deterioration, when the spoilage mechanisms affect the water properties and muscle structure.

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This study investigated the applicability of a new photochromic time-temperature indicator (TTI) to monitor the quality and shelf life of fresh cod loins in retail packs at different storage conditions; also compared this automatic monitoring method with other methods of quality control, such as sensory, chemical and microbiological analyses; and with a shelf life prediction model. TTI placed on the bottom of the packs effectively reflected the temperature condition of the product. TTI with the initial square value of 61 was suitable for continuous monitoring of the quality and shelf life of the product repacked on day 6 after processing. The estimated product shelf lives based on TTI and on the square-root model for relative rate of spoilage of fresh seafood were well correlated.

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BACKGROUND: Fish protein powder is a functional ingredient that can be used for enhancing the nutritional value of food products. In this study the effect of fortification with different levels of fish protein powder (FP) on chemical properties and sensory quality of Persian ice cream with 0, 30 and 50 g kg⁻¹ FP during storage at − 18 °C for 4 months was investigated.

RESULTS: Ice creams fortified with 50 and 30 g kg⁻¹ FP had significantly higher protein and solid-non-fat content than ice cream with 0% FP or 83, 69 and 51 g kg⁻¹ protein and 215, 204 and 181 g kg⁻¹ solid non-fat, respectively. All products had the same levels of fat, lactose, acidity and pH. They had similar sensory quality after production except for colour, but sensory properties of fortified samples changed significantly after 2 months of storage. Colour faded, cohesiveness decreased, sandiness/coarseness increased, sweetness decreased and fish flavour and off-odour increased. The control ice cream scored highest for additives odour and flavour.

CONCLUSION: Development of ice cream fortified with fish protein powder could be an effective way to enhance nutritional and functional value of ice cream. But studies on storage stability, consumers’ acceptance and attitudes are recommended if companies are planning to do so.

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Flavor characterization and quality of salt-cured and desalted cod (Gadus morhua) products was studied using sensory analysis and gas chromatography techniques. The products were produced in Iceland using two different processing methods (filleting and splitting) and three different salting procedures, i.e., the old single-step kench salting or a multistep procedure, and presalting (injection and brine salting or only brine salting), which was followed by kench salting. The main difference observed was between fillets and split fish, where the split fish was darker and had stronger flavor characteristics. Comparison of different salting procedures showed that the use of presalting improved the appearance of the salted products, which can be described as increased lightness and reduced yellowness of the products. In the same products, the intensity of curing flavors was milder, as described by sensory analysis and key aroma compounds. Derivatives from lipid and protein degradation contribute to the characteristic flavor of the salted products.

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Aims: Moritella viscosa is a Gram-negative psychrophilic bacterium that causes winter ulcer disease in farmed fish. The aim of the study was to describe an outer membrane protein of roughly 20 kDa in pathogenic M. viscosa and to compare the coincident protein of strains isolated from different fish species and geographical locations.

Methods and Results: The protein was isolated from a pathogenic strain of M. viscosa. An oligopeptide sequence obtained with MS/MS analysis showed homology to Escherichia coli OmpA and Neisseria surface protein A. The protein was named Moritella viscosa outer membrane protein 1 (MvOmp1), and sequence analysis confirmed that it is an integral membrane protein consisting of eight antiparallel β-strands, three short periplasmic turns and four long hydrophilic extracellular loops. The encoding gene, mvomp1, was fully sequenced in nine strains representing different serotypes and phenotypes. The results revealed some differences in the extracellular loops between strains. The mvomp1 gene was cloned and expressed in E. coli, and the recombinant product was recognized by anti-M. viscosa polyclonal antisera.

Conclusions: The results indicate that MvOmp1 is a major protective antigen of M. viscosa.

Significance and Impact of the Study: The results open up possibilities for use of the protein as a part of a subunit vaccine in the future.

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Although it has been known for decades that arsenic forms fat-soluble arsenic compounds, only recent attempts to identify the compounds have been successful by using a combination of fractionation and elemental and molecular mass spectrometry. Here we show that arsenolipids can directly be identified and quantified in biological extracts using reversed-phase high-performance liquid chromatography (RP-HPLC) simultaneously online-coupled to high-resolution inductively coupled plasma mass spectrometry (ICPMS) and high-resolution electrospray mass spectrometry (ES-MS) without having a lipophilic arsenic standard available. Using a methanol gradient for the separation made it necessary to use a gradient-dependent arsenic response factor for the quantification of the fat-soluble arsenic species in the extract. The response factor was obtained by using the ICPMS signal of known concentration of arsenic. The arsenic response was used to determine species-specific response factors for the different arsenic species. The retention time for the arsenic species was utilized to mine the ES-MS data for accurate mass and their tandem mass spectrometry (MS/MS) fragmentation pattern to give information of molecular formula and structure information. The majority of arsenolipids, found in the hexane phase of fish meal from capelin (Mallotus villosus) was in the form of three dimethylarsinoyl hydrocarbons (C₂₃H₃₈AsO, C₁₇H₃₈AsO, C₁₉H₄₂AsO) with minor amounts of dimethylarsinoyl fatty acids (C₁₇H₃₆AsO₃, C₂₃H₃₈AsO₃, C₂₄H₃₈AsO₃). One of the dimethylarsinoyl fatty acids (C₂₄H₃₈AsO₃), with an even number of carbon in the fatty acid chain, was identified for the first time in this work. This molecular formula is unusual and in contrast to all previously identified arsenic-containing fatty acids with odd numbers of carbon.

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