This article describes a consumer-based approach for development of new seafood product concepts among young adults in Norway and Iceland. The study aim was to gain insight into how young adults determine their acceptance of seafood and make potential product choices. Additional insights measured were confidence in seafood preparation and consumption choices when exposed to specific new seafood concepts. Based on consumer-reported values, three seafood product concepts were evaluated by 354 consumers in a web-based, conjoint experiment in Norway and Iceland. Consumers’ evaluations showed a number of consumer preferences for specific seafood product concepts partly associated with and partly conflicting with their original values. Understanding consumer attitudes can help to explain these results. The results of this study will be used as a guide for the next step in developing seafood product concepts.
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The gelation properties of protein isolates extracted from tilapia muscle with acid and alkali-aided processing were compared to washed tilapia muscle. Gels were prepared with and without the addition of 2% NaCl (w/w) slightly above neutral pH and gelation properties and gel quality were determined using various procedures. Hardness and elasticity of gels as assessed by torsion testing was improved using 2% NaCl (w/w) compared to treatments without salt. Small strain oscillatory testing showed that storage modulus (G′) of gel pastes prior to thermal gelation was significantly higher in the absence of salt, while smaller differences were seen after thermal gelation. Small strain oscillatory tests demonstrated a different gel forming mechanism for acid and alkali treated proteins compared to washed muscle. Fold tests demonstrated that acid treated proteins and washed muscle had significantly lower gel quality compared to alkali treated proteins. Addition of salt in gels improved gel water-holding capacity for acid and alkali treated proteins. Overall, the acid treated proteins exhibited poorer gelling ability compared to alkali treated proteins. Total content of SH-groups was measured before and after gelation and S–S bonding did not explain the difference in gel forming ability of different treatments. The results indicate that the alkali-aided process can be used to produce high quality protein gels from tilapia muscle suitable for manufacturing of imitation seafood products.
Angel food cake was made using egg albumen subjected to the pH-induced unfolded and refolded treatment. The effect of treatment on the rheological properties of angel food cake was investigated. Egg albumen solutions were prepared and pH was adjusted to 1.5, 4.5, 8.5 or 12.5 and then held 60 min to unfold the proteins. After holding, the solutions were readjusted to pH 4.5 or 8.5, and held for 45 min to partially refold the proteins. Egg white foam with sucrose was whipped and flour and the rest of sucrose were folded into the foam. The foam batter was heated in a TA Instrument AR 2000 controlled stress rheometer equipped in a parallel geometry. Samples were heated from 21 °C to 150 °C at a rate of 8.5 °C per min and then cooled down to 21 °C to bake the angel food cake. At 21 °C, oscillatory stress sweep was performed. There was no relationship between the G′ value of angel cake batter and its G′ value at 150 °C. Changes in rheological properties of batters and angel food cakes using different combinations of ingredients were studied. The pH unfolding and refolding procedure led to more rigid final products compared to the controls with egg albumen samples not subjected to pH treatment. Adding sucrose to the flour increased the starch gelation temperature up to 82 °C. Higher protein concentrations resulted in better foams in the cake batter, but the batter made with an intermediate protein concentration produced the most rigid angel food cake. Adding egg albumin did not change gelation temperature of the starch. It appears that incorporation of flour with the egg white foam, leads to about a ten times decrease in the strength of the foam, and a decrease in the gelatinization process of starch after adding sugar, are crucial in forming of an angel food cake texture.
The aim of this study was to use low-field nuclear magnetic resonance (NMR) and traditional chemical methods to investigate the physical and chemical differences in wild and farmed cod processed pre- and postrigor, and how these properties were affected by brine injection, brining, and freezing. In prerigor processed farmed or wild cod, brine injections followed by brining for 2 d, with brine concentrations up to 5.5% and 4%, respectively, were not sufficient to reach a muscle salt concentration of 2% as aimed for, while wild cod processed postrigor had sufficient salt uptake after the same processing. Low-field NMR gave valuable information about the differences in the muscle structure between wild and farmed cod as well as the state of the water in the muscle during brine injection, brining, and during rigor tension. Low-field NMR is, therefore, a valuable tool that can be used to optimize the salting and storing processes of lightly salted cod products from both wild and farmed cod. For farmed cod to be used in the production of lightly salted products further research is needed.
Fish protein isolates (FPI) were extracted from haddock (Melanogrammus aeglefinus) cut-offs using the pH-shift method. Flow behaviour and some functional properties of FPI containing 19% protein (pH 6.4) and different amounts of salt, sucrose and also polyphosphate stored 12 weeks at -18°C were studied. Additives influenced viscosity, but not flow behaviour. Adding salt and sucrose increased water holding capacity (WHC), but significantly decreased viscosity (Brabender Unit) and whiteness. Using polyphosphate and sucrose did not affect WHC, and whiteness of FPI but it decreased viscosity. Different amounts of additives and frozen storage time changed functional attributes of FPI significantly. The results suggest
that the isolated proteins obtained through the pH-shift also need to be preserved against denaturation during frozen storage like surimi.
The production of heavy-salted cod (Bacalao) has changed from being a single-step process (kench) salting to a multistep procedure varying between producers and countries. Presalting by injection, brining, or pickling is increasingly applied prior to pile (dry) salting. This article describes the effects of different presalting methods (injection and brining, brining only, and pickling) on yield and chemical composition of salted cod fillets, in comparison to a single-kench salting step. The procedures used influenced the weight yields and chemical composition of the products. Injection was significantly different from other methods in increasing weight yields throughout brining, dry salting, and rehydration. The yield of nitrogenous compounds tended to be lower for injected and brine-salted fillets, mainly due to higher losses of nonprotein nitrogen.
This article documents the addition of 228 microsatellite marker loci to the Molecular Ecology Resources Database. Loci were developed for the following species: Anser cygnoides, Apodemus flavicollis, Athene noctua, Cercis canadensis, Glis glis, Gubernatrix cristata, Haliotis tuberculata, Helianthus maximiliani, Laricobius nigrinus, Laricobius rubidus, Neoheligmonella granjoni, Nephrops norvegicus, Oenanthe javanica, Paramuricea clavata, Pyrrhura orcesi and Samanea saman. These loci were cross-tested on the following species: Apodemus sylvaticus, Laricobius laticollis and Laricobius osakensis (a proposed new species currently being described).
Juvenile Atlantic halibut (40.5 ± 9.1 g mean initial body mass ± SD) were reared at five different levels of oxygen availability (57%, 84%, 100%, 120%, and 150% of air saturation) for 94 days. The availability of oxygen significantly affected the growth rate of the fish while feed conversion was not significantly different. The final size of fish reared at 57% of air saturation was significantly lower than in groups reared at 100% to 150% of air saturation and the specific growth rate (SGR) in the 57% group over the 94 day period was significantly lower than in all other groups. The increase in biomass was 45% higher in the group exposed to 100% of oxygen saturation than in the group reared at 57% saturation. The group reared at 84% of air saturation was intermediate and the final size of this group was significantly different from fish reared at either 57% or 100%–150% of air saturation. There was no significant difference in the growth trajectories of fish reared at 100%–150% of air saturation but they were significantly different from those of fish reared at either 57% or 84% saturation. This suggests that the growth of halibut is progressively increased when the oxygen saturation is increased from 57% to 100% while further increase in oxygen saturation does not improve the growth rate. When oxygen saturation was increased, the blood pH increased as did the partial pressure of CO2, total concentration of CO2 and bicarbonate in blood. This change is likely a result of reduced ventilation rate with increased oxygen saturation. The results challenge the common recommendation that 60%–80% oxygen saturation is adequate to support maximum growth of fish. The results of the present study suggest that there may be an advantage for halibut farmers to increase the oxygen availability from the recommended 60%–80% oxygen saturation up to 100%.
An intervention study was conducted at early juvenile stage of Atlantic cod (Gadus morhua L.) rearing to confirm the properties of two prospective probionts, Arthrobacter sp. and Enterococcus sp. isolated from a cod hatchery. Juveniles (10 g) were fed expanded dry feed for 28 or 55 days, either untreated or treated with the probiotic bacteria in mixture or singly (107–9 CFU g−1 feed). Viability of probionts supplemented to the feed was evaluated during a two-month storage at −20, 4 and 15 °C and sensory evaluation of the probiotic feed performed at the end of storage. Juvenile growth, survival, feed conversion ratio, and microbial load of rearing water, juvenile gills and gut were examined. Microbiological stability of the probionts added to the feed was demonstrated at all temperatures, while sensory evaluation detected faint oxidative off-odours in feed stored frozen. Juveniles fed the Enterococcus-probiotic feed grew significantly faster and had significantly lower gut Vibrio counts than control juveniles (p < 0.05). Overall, the results suggest that both probionts, especially the Enterococcus strain, modified the gut microbiota and contributed to enhanced juvenile growth and survival.
Proteome analysis was used to study the effects of feeding early Atlantic cod (Gadus morhua) larvae with a saithe (Pollachius virens) protein hydrolysate (SPH). Protein hydrolysates have previously been shown to beneficially affect fish larval development. Feeding was initiated on day 2 post hatch (ph) or as soon as the larvae opened their mouth and the protein expression was monitored 4 days later or in 6-dph cod larvae. The results demonstrated changes in the abundance of 13 protein spots in the cod larvae fed SPH. Of these, seven protein spots were up-regulated and six protein spots showed down-regulation. Five of the up-regulated proteins in cod larvae are known to be involved in energy metabolism. A few early larval specific proteins were down-regulated in the SPH-fed cod larvae possibly because of an enhanced development in this group relative to the control group. Two trypsin isoforms were detected within the cod larval proteome. The detection of the trypsin spots was made possible by co-electrophoresis of known cod trypsins with the cod larval protein extract. Surprisingly, no difference in trypsin content was observed between the SPH-fed and the control larval groups.