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Fish protein isolate (FPI) made from haddock (Melanogrammus aeglefinus) cut-offs by the pH-shift process was added to haddock mince to make two groups of fried fish balls. The proportions (%) of mince to isolate were 100: 0 (control group), 75:25 and 50:50. All groups were air packed and kept frozen at −18C. The sample groups were evaluated by sensory evaluation 1 day after processing and after 2, 4 and 8 weeks of storage at −18C. The results indicated that added FPI to mince and frozen storage affected the odor, flavor, texture and appearance of fish balls significantly, possibly because of chemical and biochemical changes of all groups. This study also revealed that most negative features are attributed to the groups containing 50% mince and 50% isolate. The results can be considered for product development of FPI.

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Sensory characteristics of farmed cod exposed to low or conventional stress levels prior to slaughter were evaluated by a trained sensory panel. Consumers in two different settings, central location test (CLT) and home-use test (HUT), also tasted the products and rated them according to overall liking on a 9-point hedonic scale and sensory attributes on a 9-point intensity scale. Differences were observed in texture attributes of the two cod groups by the trained sensory panel. Consumers in the CLT distinguished between the two cod groups whereas consumers in the HUT setting did not. Consumers in the CLT scored the products lower with regard to liking, and evaluated sensory attributes differently from consumers in the HUT setting. The results indicated that the cooking method chosen by consumers in the HUT setting influenced the consumer evaluation of cod. Similar cooking methods used in CLT and HUT produced similar results of liking.

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Sensory characteristics of cod products available to consumers were analyzed, and different ways to analyze sensory results were viewed. Ten cod samples of different origin (wild and farmed cod), storage time (short and extended) and storage method (stored fresh, frozen or packed in modified atmosphere) were evaluated with quantitative descriptive analysis by a trained sensory panel. Signal-to-noise analysis, p * MSE (discrimination and repeatability) and line plots proved to be very useful in studying panelists' performance. Most sensory attributes described significant differences between the products, and principal component analysis provided an overview of the differences and similarities between the products with regard to sensory characteristics. Farmed cod had different sensory characteristics compared to wild cod, such as more meat flavor, and rubbery and meaty texture. Different storage methods had minor influence on sensory characteristics of cod fillets after short storage time, but after extended storage, the groups were different with regard to most attributes.

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The effects of Fucus vesiculosus extract and fractions towards haemoglobin- (Hb-) catalysed lipid oxidation in washed cod muscle system and cod protein isolates during ice storage were examined. The extract and fractions were characterized in terms of total phlorotannin content (TPC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, ferrous ion-chelating ability and reducing power. Progression of oxidation was followed by determining rancid odor, thiobarbituric acid reactive substances (TBARS), redness and volatile oxidation compounds by gas chromatography (GC). In both washed cod muscle and protein isolates, phlorotannin-enriched ethyl acetate (EtOAc) fraction showed higher inhibitory effect than crude 80% ethanol (EtOH) extract. The addition of oligomeric phlorotannin-rich subfraction (LH-2) separated by Sephadex LH-20 chromatography, completely inhibited the initiation of lipid peroxidation in both systems throughout the entire study period (8 days). Its effectiveness at 300 mg / kg level was comparable to that of 100 mg / kg propyl gallate (PG), a highly effective synthetic antioxidant in muscle foods. Although polymeric phlorotannin-rich subfraction (LH-5) had similar level of TPC and chemical antioxidant activities as oligomeric subfraction LH-2, it was far less efficient in model systems. These results suggest that other factors rather than the intrinsic reactivity toward radicals could be responsible for the inhibitory effect of phlorotannins on lipid oxidation in fish muscle. This study highlights the great potential of oligomeric phlorotannins as novel natural antioxidants in fish and fish products.

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Effective cooling of newly caught fish is of great importance to inhibit bacterial growth and therefore increase quality, safety and shelf life of the product. In this study, two commercial cooling media (liquid ice A and B) were tested and their performance was compared to conventional plate ice during chilled 8-day storage of whole, gutted haddock. Temperature was monitored, and deteriorative changes were followed by conventional microbiological counts [(total viable psychrotrophic; specific spoilage organisms and physicochemical methods (pH, TVB-N, TMA, salt content)]. A cultivation-independent method (16S rRNA clone analysis) was used to study the effect of cooling treatments on the bacterial community of haddock initially and at the end of storage. The results show that the bacterial growth behavior observed for differently cooled fish was not supported by their temperature profiles. Growth of the SSOs, Photobacterium phosphoreum and H₂S-producing bacteria was delayed at early storage, independently of the cooling methods. With further storage, little or no count differences were seen among traditionally iced fish and those cooled in liquid ice with a top ice layer. At the end of storage, significant (p < 0.05) increase in P. phosphoreum and H₂S-producing bacteria counts of skin and flesh sampled from liquid ice with no top ice layer was observed along with higher salt, TVB-N and TMA flesh content. Cultivation-independent analysis confirmed the dominance of P. phosphoreum in fish stored in liquid ice B with no top layer (up to 76% dominance) and liquid ice A with top layer (44% dominance). Psychrobacter and Flavobacterium dominated the microbiota of fish stored in conventional plate ice and liquid ice B with ice top layer. The study shows that the use of liquid ice prepared from brine provides faster initial cooling of whole fish but may create unfavorable conditions under extended storage where the active spoiler P. phosphoreum becomes dominant. Plate ice may therefore be an optimal medium for extended fish storage.

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BACKGROUND: Fish protein powder (FPP) is used in the food industry for developing formulated food products. This study investigates the feasibility of increasing the value of saithe (Pollachius virens) by producing a functional FPP. Quality attributes of spray and freeze-dried saithe surimi containing lyoprotectants were studied. A freeze-dried saithe surimi without lyoprotectants was also prepared as a control sample.

RESULTS: The amount of protein, moisture, fat and carbohydrate in the FPPs were 745–928, 39–58, 21–32 and 10–151 g kg⁻¹. Quality attributes of FPPs were influenced by the two drying methods and lyoprotectants. The highest level of lipid oxidation was found in the control and the second highest in the spray-dried FPP. The spray-dried fish protein had the lowest viscosity among all FPPs. Gel-forming ability of samples with lyoprotectants was higher than that of the control. Water-binding capacity, emulsion properties and solubility of the freeze-dried fish protein containing lyoprotectants were significantly higher than spray-dried and control samples. However, functional properties of spray-dried FPP were higher than the control sample.

CONCLUSION: It is feasible to develop value-added FPP from saithe surimi using spray- and freeze-drying processes, but freeze-dried FPP containing lyoprotectant had superior functional properties and stability compared with spray-dried sample. Both products might be used as functional protein ingredients in various food systems. Copyright © 2010 Society of Chemical Industry

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Background

International fish trade reached an import value of 62.8 billion Euro in 2006, of which 44.6% are covered by the European Union. Species identification is a key problem throughout the life cycle of fishes: from eggs and larvae to adults in fisheries research and control, as well as processed fish products in consumer protection.

Methodology / Principal Findings

This study aims to evaluate the applicability of the three mitochondrial genes 16S rRNA (16S), cytochrome b (cyt b), and cytochrome oxidase subunit I (COI) for the identification of 50 European marine fish species by combining techniques of “DNA barcoding” and microarrays. In a DNA barcoding approach, Neighbor Joining (NJ) phylogenetic trees of 369 16S, 212 cyt b, and 447 COI sequences indicated that cyt b and COI are suitable for unambiguous identification, whereas 16S failed to discriminate closely related flatfish and gurnard species. In course of probe design for DNA microarray development, each of the markers yielded a high number of potentially species-specific probes in silico, although many of them were rejected based on microarray hybridization experiments. None of the markers provided probes to discriminate the sibling flatfish and gurnard species. However, since 16S probes were less negatively influenced by the “position of label” effect and showed the lowest rejection rate and the highest mean signal intensity, 16S is more suitable for DNA microarray probe design than cty b and COI. The large portion of rejected COI probes after hybridization experiments (> 90%) renders the DNA barcoding marker as rather unsuitable for this high-throughput technology.

Conclusions / Significance

Based on these data, a DNA microarray containing 64 functional oligonucleotide probes for the identification of 30 out of the 50 fish species investigated was developed. It represents the next step towards an automated and easy-to-handle method to identify fish, ichthyoplankton, and fish products.

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Nine thermophilic strains of aerobic, non-sporulating, heterotrophic bacteria were isolated after enrichment of chimney material sampled from a deep-sea hydrothermal field at a depth of 2634 m on the East-Pacific Rise (1 ° N). The bacteria stained Gram-negative. They were rod-shaped and measured approximately 0.5 μm in width and 1.5–3.5 μm in length. They grew at 55–80 ° C, pH 6–8 and 1–6 % NaCl. Optimal growth was observed at 70–75 ° C, pH 7.0 and 1–3 % NaCl. The organisms were identified as members of the genus Rhodothermus, having a 16S rRNA gene similarity of 98.1 % with Rhodothermus marinus DSM 4252^T. The novel isolates differed morphologically, physiologically and chemotaxonomically from R. marinus, eg in lack of pigmentation, response to hydrostatic pressure, maximum growth temperature and DNA G + C content. DNA – DNA hybridization revealed a reassociation value of 37.2 % between strain PRI 2902^T and R. marinus DSM 4252^T, which strongly suggested that they represent different species. Furthermore, AFLP fingerprinting separated the novel strains from R. marinus reference strains. It is therefore concluded that the strains described here should be classified as representatives of a novel species for which the name Rhodothermus profundi sp. nov. is proposed; the type strain is PRI 2902^T (= DSM 22212^T = JCM 15944^T).

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