Effects of food container depth on the quality and yield of superchilled and iced Atlantic salmon

Insulated food containers of different sizes are commonly used to preserve the quality of perishable fresh fish products during transport and storage. The aim of the study was to explore the effects of packaging solutions with various depths on the quality of iced and superchilled farmed Atlantic salmon (Salmo salar). Insulated containers of different depths (32, 42, and 60 cm) and 17-cm deep expanded polystyrene (EPS) boxes were used to simulate transport and storage of the fish. The fish quality was evaluated after 4, 10, and 14 days of storage, where measurements on drip loss, texture, cooking yield, sensory evaluation, water and lipid distribution, and characteristics analysis in the fish muscle by nuclear magnetic resonance (NMR) spectroscopy were performed. Increased container depth from 32 to 42 cm increased the drip loss of superchilled salmon from 2.4% to 3.1% after 10 days of storage at −1°C. Iced storage of salmon for 10 days in EPS boxes resulted in less drip loss (0.5%) compared with superchilled salmon (1.5%) stored in EPS. The NMR analysis, sensory evaluation, texture analysis, and cooking yield did not reveal any major differences between salmon stored in containers of different depths. Iced storage increased pressure marks as compared with non-iced, superchilled storage in insulated containers. The results indicate that transport of whole salmon in reusable insulated plastic containers with a depth of 60 cm is possible without major quality changes observed for up to 10 days.     

Characteristics and nutritional value of biscuits fortified with debittered salmon (Salmo salar) frame hydrolysate

Effect of debittered salmon frame hydrolysate (DSFH) at various levels (0, 5, 10, 15, 20 and 25 g/100 g) on physicochemical, textural, sensory and nutritional properties of biscuits was investigated. The highest thickness was obtained for the sample with 25 g/100 g DSFH (P < 0.05). There was no difference in diameter among all the biscuit samples (P > 0.05). The samples added with DSFH had lower weight, water activity and moisture content than the control (CONT, without DSFH) (P < 0.05). DSFH at 15 g/100 g showed no detrimental effect on sensory properties of resulting biscuits (DSFH-15). The DSFH-15 biscuit showed reduction in cutting force and fracturability. Scanning electron microscopic and cross-sectional images showed that DSFH-15 biscuit had more porous structure, compared to the CONT. The biscuits fortified with 15 g/100 g DSFH had higher protein but had lower energy value, fat and carbohydrate content than the CONT.     

油煎工艺条件对香煎大麻哈鱼品质的影响

以黑龙江特色菜肴"香煎大麻哈鱼"为研究对象,主要探究不同油煎温度(145,150,155,160,165℃)和时间(6,7,8,9,10min)对香煎大麻哈鱼品质的影响。通过单因素试验分别对香煎鱼肉的剪切力、出品率、水分含量和感官质量进行测定,筛选出最佳的加热工艺。结果表明,香煎大麻哈鱼最佳的油煎条件为在油温155℃时油煎8min,此时鱼肉最嫩,出品率较高,水分含量最大,感官评价得分最高,表现为肉质多汁性、口感等感官品质最佳。     

Characterizing physical habitat preferences and thermal refuge occupancy of brook trout (Salvelinus fontinalis) and Atlantic salmon (Salmo salar) at high river temperatures

Anthropogenic influences, including climate change, are increasing river temperatures in northern and temperate regions and threatening the thermal habitats of native salmonids. When river temperatures exceed the tolerance levels of brook trout and Atlantic salmon, individuals exhibit behavioural thermoregulation by seeking out cold‐water refugia – often created by tributaries and groundwater discharge. Thermal infrared (TIR) imagery was used to map cold‐water anomalies along a 53 km reach of the Cains River, New Brunswick. Trout and salmon parr did not use all identified thermal anomalies as refugia during higher river temperature periods (>21°C). Most small‐bodied trout (8–30 cm) were observed in 80% of the thermal anomalies sampled. Large‐bodied trout (>35 cm) required a more specific set of physical habitat conditions for suitable refugia, that is, 100% of observed large trout used 30% of the anomalies sampled and required water depths >65 cm within or adjacent to the anomaly. Densities of trout were significantly higher within anomalies compared with areas of ambient river temperature. Salmon parr were less aligned with thermal anomalies at the observed temperatures, that is, 59% were found in 65% of the sampled anomalies; and densities were not significantly different within/ outside anomalies. Salmon parr appeared to aggregate at 27°C, and after several events over 27°C variability in aggregation behaviour was observed – some fish aggregated at 25°C, others did not. We stipulate this is due to variances of thermal fatigue. Habitat suitability curves were developed for velocity, temperature, depth, substrate, and deep water availability to characterize conditions preferred by fish during high‐temperature events. These findings are useful for managers as our climate warms, and can potentially be used as a tool to help conserve and enhance thermal refugia for brook trout and Atlantic salmon in similar systems.     

The control of sea lice in Atlantic salmon by selective breeding

Sea lice threaten the welfare of farmed Atlantic salmon and the sustainability of fish farming across the world. Chemical treatments are the major method of control but drug resistance means that alternatives are urgently needed. Selective breeding can be a cheap and effective alternative. Here, we combine experimental trials and diagnostics to provide a practical protocol for quantifying resistance to sea lice. We then combined quantitative genetics with epidemiological modelling to make the first prediction of the response to selection, quantified in terms of reduced need for chemical treatments. We infected over 1400 young fish with Lepeophtheirus salmonis, the most important species in the Northern Hemisphere. Mechanisms of resistance were expressed early in infection. Consequently, the number of lice per fish and the ranking of families were very similar at 7 and 17 days post infection, providing a stable window for assessing susceptibility to infection. The heritability of lice numbers within this time window was moderately high at 0.3, confirming that selective breeding is viable. We combined an epidemiological model of sea lice infection and control on a salmon farm with genetic variation in susceptibility among individuals. We simulated 10 generations of selective breeding and examined the frequency of treatments needed to control infection. Our model predicted that substantially fewer chemical treatments are needed to control lice outbreaks in selected populations and chemical treatment could be unnecessary after 10 generations of selection. Selective breeding for sea lice resistance should reduce the impact of sea lice on fish health and thus substantially improve the sustainability of Atlantic salmon production.     

Physicochemical and microbial changes during storage of smoke-flavoured salmon obtained by a new method

The aim of this study was to evaluate the effect of a new smoking-salting method employing water vapour permeable (WP) bags on the physicochemical and microbial quality of smoke-flavoured salmon in refrigerated storage. Fresh salmon was subjected to a smoking process in the WP at 5 °C. Physicochemical and microbiological analyses were periodically carried out during the subsequent 40 days of refrigerated storage of the product. The WP bags enabled the evaporation of the exudate during the smoking-salting stage, enabling the drying of the product to take place at the same time. A slight increase of trimethylamine nitrogen (TMA-N) and total volatile basic nitrogen (TVB-N) contents was observed over the storage period. The concentration of TVB-N ranged from 14.26 to 21.48 mg N/100 g of fish, values far below the upper limits of acceptability. The low values of the thiobarbituric acid (TBA) index (final level of 0.71 mg MDA/kg) indicate that the lipid oxidation in the smoke-flavoured salmon was limited throughout the period studied. The initial K₁-value was high and only a slight increase was observed during storage. Counts of mesophilic, psychrotrophic, Enterobacteriaceae and lactic acid bacteria were low throughout the study. Given the changes observed for the physicochemical and microbiological parameters, it can be said that no spoilage took place in the smoke-flavoured salmon during the 40 days of storage. This new method could be of interest to producers as it enables smoke-flavoured salmon to be produced to a good standard of hygiene, minimizing handling and reducing processing steps and brine wastes.     

Qualitative risk assessment of introduction of anisakid larvae in Atlantic salmon (Salmo salar) farms and commercialization of products infected with viable nematodes

In this study, the likelihood of introduction of anisakid larvae in Atlantic salmon (Salmo salar) farms and subsequent commercialization of fish infected by at least one vital parasite was formally assessed using an adaptation of the risk assessment framework for importation of animals and animal products of the World Organization for Animal Health (OIE). The different plausible pathways were identified and outlined. The most recent information concerning the parasite, its definitive, intermediate hosts and the farming practices typical of Atlantic salmon farms were reviewed and used to assess the likelihoods of each key step along the pathways. A matrix for the conditional probabilities was adopted to combine the qualitative estimations and obtain an objective and transparent overall risk of introduction along each route. In order to avoid misinterpretation and overconfidence on the outcome, the uncertainties surrounding the estimations were considered. The only situation for which the assessed risk in a typical Atlantic salmon farm was deemed to be non-negligible involved the ingestion of infected hosts that penetrate the harvesting cages. In this event, the overall risk was estimated as ‘Very Low’ with a high degree of uncertainty because of the scarcity of information in some of the key steps along the pathway. However, the scientific evidence in support of the overall estimation suggests that the availability of additional data would be unlikely to increase the final estimated risk. On the basis of the available information of the system, the estimated risk of introduction and commercialization of farmed Atlantic salmons infected by viable nematodes resulted ‘Very Low’ even under a conservative approach. The proposed qualitative model is an objective and transparent method to assess the risk when data and information are scarce and provides a framework for the qualitative assessment of the introduction of alive parasites in aquaculture/mariculture implants and subsequent commercialization of infested fishery products. The framework could be easily adapted to other parasite-host interactions besides anisakid nematodes in Farmed Atlantic salmons.     

Sensory characteristics and storage quality indicators of surimi franks nutritionally enhanced with omega‐3 rich flaxseed oil and salmon oil

Surimi franks were fortified with flaxseed or salmon oil at 2 g/100 g sample, franks without added oil served as a control. Thiobarbituric acid reactive substances values were highest (P < 0.001) in salmon oil franks; however, these values did not change over the 21‐day storage period regardless of frank type (P > 0.05). Frank pH decreased over time (P = 0.011) for all frank types. There were differences in textural properties between frank types (P < 0.05), with the flaxseed franks being softer and less gummy, cohesive and chewy than the control franks. Participants (n = 79; age 18–35) evaluated visual appeal, colour, aroma, texture, flavour and acceptability on a hedonic scale; there were no differences (P > 0.05) between franks. Fifty‐four panellists reported consuming sausage on a weekly to monthly basis, and most (50/79) indicated interest in purchasing this type product. The surimi franks were accepted by young adult consumers, which may indicate market potential of these types of products.     

Habitat use and diet composition of juvenile Atlantic salmon in a tributary of Lake Ontario

The habitat use and diet of juvenile Atlantic salmon Salmo salar was examined in the South Sandy Creek drainage that discharges into eastern Lake Ontario. Subyearling salmon were stocked in early May during two consecutive years, and habitat and diet evaluations were made in mid-July and mid-October in 2005 and 2006. Both subyearling and yearling Atlantic salmon occupied deeper and faster areas that had more cover and larger sized substrate materials than was present, on average, within the study reach. Differences in habitat use between subyearling and yearling salmon only occurred in summer. Principal component analysis showed that of the habitat variables examined, the amount of cover and size of substrate were more important to juvenile salmon in summer, whereas depth and velocity were more important in the fall. Trichopteran larvae (mainly hydropsychids) dominated the diet of juvenile Atlantic salmon, and parr were feeding most heavily from the substrate as compared to the drift. The juvenile ecology of this re-introduced population of Atlantic salmon is consistent with that reported in other studies throughout the species native range.