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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 with 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 characterised 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 odour, 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 behaviour 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 unfavourable 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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