Low salt brining of pre-rigor filleted farmed cod (Gadus morhua L.) and the effects on different quality parameters

Pre-rigor processing of cod fillets may have economic benefits, but this potential has usually been overshadowed by process-linked difficulties such as pin bone removal, rapid rigor onset and higher drip losses. The aim of this work was to study the impact on fillet quality parameters after immersing pre-rigor filleted farmed cod in different NaCl solutions ranging from 15 to 60 g/L. Temperature of the fish at death was 4 °C, in immersion solutions 2 °C, and following immersion the fillets were stored in ice within plastic bags for 14 days. As controls, one group was filleted pre-rigor but not immersed, and one group was filleted post-rigor and not immersed. Immersing in salt solution resulted in better yield compared to both control groups. Higher salt content generally increased rigor contraction, but significantly reduced fillet gaping and the force required to pull pin bones. Thus, relatively low salt levels within the fillets had a positive impact on some of the problems associated with pre-rigor filleting.     

The effects of salt-curing and salting procedures on the microstructure of cod (Gadus morhua) muscle

The aim of this study was to investigate the effects of salting and different pre-salting procedures (injection and brining versus brining only) on the microstructure and water retention of heavy salted cod products. Salting resulted in shrinkage of fibre diameter and enlargement of inter-cellular space. Water was expelled from the muscle and a higher fraction became located in the extra-cellular matrix. These changes were suggested to originate from myofibrillar protein aggregation and enzymatic degradation of the connective tissue. During rehydration, the muscle absorbed water again and the fibers swelled up to a similar cross-sectional area as in the raw muscle. However, the inter-cellular space remained larger, resulting in a higher water content of the muscle in the rehydrated stage. The effects of different salting procedures were strongest after salting. At that stage of the process, the inter-cellular space tended to be larger in the injected and brined muscle than in the brined only.     

The effect of filleting and ice application on the quality and safety of Atlantic bonito (Sarda sarda) at refrigerated storage

Filleting effect of refrigerated bonito with and without ice on the quality changes and food safety was investigated. Significant variations occurred (P < 0.05) in sensory, chemical and microbiological values amongst groups. The best sensory results were found for filleted bonito with ice (FBRI) with a shelf‐life of 13 days. While sensory values decreased significantly during storage, opposite situation occurred for both chemical and microbiological results (P < 0.05). The lowest total volatile basic nitrogen value was also observed with FBRI and was within the acceptable levels for 15 days as 17.86 mg 100 g^?1. All samples contained acceptable trimethylamine levels for 15 days despite unacceptable sensory values after certain days. Although filleting seemed to increase the lipid oxidation, ice application resulted in lowering thiobarbituric acid content. Histamine results closely supported sensory values in terms of legally permitted levels usually by set FDA. While WBR contained histamine value over EU permitted level as 113.78 ppm on the 7th day, the value for FBRI was 56.13 ppm on the 15th day. Histamine‐forming bacteria counts supported histamine formation in most groups, while total bacteria counts were in agreement with sensory results. This study suggests that using ice and filleting can improve shelf‐life of bonito stored at refrigerated temperatures in terms of food quality and safety.     

Effects of catching methods on quality changes during storage of cod (Gadus morhua)

The catching method, storage time and composition of fish are factors that influence the quality of fish. Different opinions have been expressed concerning the effect of catching methods on the fish quality. In this work cod caught at the same time and location, using different catching methods (gillnet and longline) has been stored for up to 16 days. The same soaking time was used for both fishing gears. No differences due to fishing gear was observed in the quality attributes QIM score, water content, TVN, DMA, TMA, TMAO, Freshmeter-readings, total viable count, sulphide producing bacteria and P. phosphoreum during storage. The catching method had significant influence on pH only. It is shown that the pH of the fish caught by gillnet is lower than pH of fish caught by longline. It is also shown that fish caught by gillnet have higher K-factor than fish caught by longline. The pH of the fish muscle is closely correlated to K-factor; higher K-factor supports lower pH.It is also shown that by using the quality parameters water content, TVN, DMA, QIM score, Freshmeter-readings, TVC, sulphide producing bacteria, and P. phosphoreum, the storage time in ice can be predicted with a correlation of 0.99 and a prediction error of 0.8 day.     

Water-holding capacity of wild and farmed cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) muscle during ice storage

The aim of this study was to investigate how the presence of normal spoilage bacteria influenced the water-holding capacity (WHC) of wild cod, farmed cod and haddock during chilled storage. Bacterial growth was inhibited by soaking the fillets in 3 mmol/l NaN₃ prior to storage. The results clearly showed that the three groups were different with respect to WHC and pH. Muscle pH was highest in haddock, lower in wild cod and lowest in the farmed cod. Significant differences in WHC between the NaN₃-treated and nontreated groups of wild cod and haddock were found on the last sampling day. However, there was an inconsistency with respect to the relationship between pH and percentage liquid loss (LL%). The microflora of farmed cod is obviously altered from what is normal for wild cod. The results showed that bacterial growth may influence the WHC of the muscle. However, the relationship is inconsistent and may be temporal and not causative.     

Effect of salt and MTGase on the production of high quality gels from farmed sea bass

In order to obtain low salt fish products, the effects of the addition of 0.5% (w/w based on whole product, wp) MTGase and different levels (0.25%, 0.50%, 1.00% and 2.50%, w/w wp) of sodium chloride salt to heat-induced gels from farmed sea bass (Dicentrarchus labrax) trimmings were tested and compared with gels without salt and/or without MTGase.MTGase and salt addition, both, had a favourable effect on texture. However, only salt incorporation augmented water holding capacity (WHC).A synergistic effect was detected between MTGase and salt for several important textural properties, particularly, gel strength, which reached 64.3 ± 8.1 N mm, a value comparable to those of best quality surimi. Moreover, MTGase required addition of salt to the product for its effect to be felt, however only a minimal amount (0.25%, w/w wp) sufficed. In fact, the addition of MTGase enabled reduction in salt content to 1.0% (w/w wp), without significant loss of textural and overall quality.     

Formulation and stability of biodegradable films made from cod gelatin and sunflower oil blends

Sunflower oil was added to cod gelatin in proportions of 0%, 0.3%, 0.6%, and 1% to improve the hydrophobic properties of the resulting films and decrease water vapor permeability and the soluble matter content. Mechanical and optical properties were evaluated to determine the influence of the added oil and the stability of the films during storage for one month. Adding oil increased film thickness, whiteness, optical absorbance and decreased transparency; all these properties held stable over the storage period. Fourier transform infrared (FTIR) spectra revealed some lipid–protein interactions (hydrogen bonds, ester formation) and early oil oxidation. By the end of storage oxidation was well advanced and secondary oxidation products were present. Adding oil in any quantity decreased the puncture force but not the puncture deformation. Stability of these two mechanical properties decreased during storage in the films that contained ?0.6% added oil. Water vapor permeability did not decrease when oil was added and even increased with storage time, though adding oil yielded more insoluble films due to lipid–protein interactions.     

High resolution two-dimensional electrophoresis as a tool to differentiate wild from farmed cod (Gadus morhua) and to assess the protein composition of klipfish

Tris and CHAPS–urea extracts from wild and farmed cod muscle and from rehydrated cod klipfish fillets were analyzed by one (1DE) and two-dimensional electrophoresis (2DE). 2DE maps of tris extracts from farmed cod differed from the wild in a series of spots of Mw 35 and 45 kDa. The CHAPS–urea extracts from farmed cod had a several spots of Mw between 100 and 45 kDa, which were hardly detectable in wild cod and very prominent in klipfish. Klipfish was clearly different from the other samples: the myosin heavy chain was hardly detectable in these samples, and the tris extracts contained fewer, and the CHAPS–urea more spots than the corresponding extracts from the raw muscles. Further identification of these potentially diagnostic spots will make it easier the differentiation of farmed from wild cod and the evaluation of klipfish processing on the protein content of the product.     

Influence of the oxidative quality of dietary oil on broiler meat storage stability

Broilers were fed a high fat diet containing 11% oil (9% rapeseed oil, 2% soya bean oil) and the oil was given either as fresh (peroxide value of 1 meqv. O₂kg⁻¹ oil) or as highly oxidised (peroxide value of 156 meqv. O₂kg⁻¹ oil). Diets were supplemented with 46 mg all-rac--tocopheryl acetate kg⁻¹ diet, resulting in a tocopherol content of 80.8 mg -tocopherol and 58.6 mg γ-tocopherol per kg diet in the fresh oil diet and of 44.0 mg -tocopherol and 18.3 mg γ-tocopherol per kg diet in the oxidised oil diet, respectively, reflecting the degradation of the natural occurring tocopherols in the oxidised diet. Only minor differences were seen with respect to fatty acid composition in muscles from birds fed the two diets. The oxidation of the dietary oil lowered lipid stability significantly (p < 0.01) in both raw and precooked meats during chill storage, whereas only minor effects on the stability of frozen meat were seen. Tocopherol levels were significantly lower (p < 0.01) in muscles from birds fed the oxidised oil diet, explaining the decreased lipid stability of meat from these birds. Thigh meat was more susceptible to lipid oxidation during storage than breast meat, regardless of dietary treatment, although thigh meat had markedly higher tocopherol levels than breast meat. The molar ratio of PUFA > 18:2 (polyunsaturated fatty acids with three or more double bonds) to -tocopherol was significantly (p < 0.01) higher in thigh meat compared with breast meat, explaining the lower stability of the former during storage.     

Influence of salt concentration on the salting kinetics of cod loin (Gadus morhua) during brine salting

The influence of different salt concentrations of 6%, 15%, 18% and 24% (w/w) on mass transfer of water and salt during brine salting of cod loins was studied. An increase in salt concentration accelerated water exudation and salt diffusion in the cod loins. Weight gain of the cod loins increased with decreasing salt concentration and the cod loins in the 6% brine had the highest process yield. The salting kinetic parameter values for total and water weight changes decreased with increasing salt concentration. Inversely, higher salting kinetic parameter values for salt weight changes were observed for higher brine concentrations. The samples brined at 18% and 24% had identical effective diffusion coefficients and the highest effective diffusion value was found in the cod loins brined at 15%.     

Influence of HPP conditions on selected beef quality attributes and their stability during chilled storage

The aim of this work was to determine the effects of combined pressure and temperature treatments on beef quality attributes after processing and during chilled storage. Beef M. pectoralis profundus samples were pressurised at 400 and 600 MPa at 35, 45 and 55°C and compared with non-treated (NT) and oven cooked samples. High pressure processing (HPP) at higher temperatures (55°C) resulted in lower Warner Bratzler Shear Force (WBSF) and cook loss values than processing at 35°C. Thiobarbituric acid reactive substances (TBARS) values of pressurised samples were lower than cooked samples after processing and throughout refrigerated storage. An increase (p<0.001) in the omega 6/omega 3 (n6/n3) fatty acid ratio was found when pressure-temperature treatments were compared to raw samples, however, oven cooked samples presented the highest n6/n3 ratio among all of the treatments examined. The reported results show that HPP alters meat quality to a lesser extent than conventional cooking, thereby minimising the processing impact.     

The influence of different acids and pepsin on the extractability of collagen from the skin of Baltic cod (Gadus morhua)

Solutions of (0.5 M) citric, lactic and acetic acids and 0.15 M HCl were used for the extraction of collagen from the whole skins of Baltic cod (Gadus morhua). The extractions were performed at a temperature of 4 °C for 24, 48 and 72 h using a solid/solution ratio of 1:6 (w/v). Of the acids used, HCl was the least effective solvent for collagen. The maximal yield of collagen extracted with citric acid was 60%. Collagen extraction with acetic or lactic acid give a maximal yield of about 90% with HCl yielding of only 18%. After enzymatic treatment of cod skin the yield of protein extracted with HCl and citric acids increased to 40% and 20%, respectively. Collagen was completely solubilized under the same conditions in acetic and lactic acids. Electrophoretic analysis of collagens extracted in HCl and citric acids with enzymatic treatment proved that the isolated protein was denaturated. The solutions of acetic and lactic acids are solvents for native collagen.     

Effect of season and fishing ground on the activity of cathepsin B and collagenase in by-products from cod species

Cathepsin B and collagenase are important enzymes in the quality-deteriorating processes of fish products. Fish by-products are the left-overs after preparation of the main product and are highly perishable fractions of the fish. They do, however, contain high-quality protein with a potential for utilization. This study characterizes the activity of cathepsins B and collagenase in by-products from five species of cod caught in different fishing grounds and in different seasons. Mean maximum cathepsin B activity was measured at 35 °C in the viscera and the liver, and 50 °C in cut off, while collagenase showed mean maximum activity at 20 °C in cut off, 35 °C in liver and 50 °C in viscera. Species, season and fishing ground significantly affected activity of cathepsin B and collagenase in cut off samples, while viscera samples were not significantly affected. Cathepsin B was more heat stable than collagenase in all three fractions. Both cathepsin B and collagenase from cut off were less heat stable than the corresponding enzymes from the other two fractions.     

Effect of diet and season on quality of farmed Atlantic cod (Gadus morhua L.)

Three groups of farmed Atlantic cod (Gadus morhua L.) fed dry or moist feeds were followed through a production cycle from 800 to 2500 g. Five samplings were made at quarterly intervals; December, March, June, September and December. At each sampling, fillet yield, skin colour and muscle pH were measured at slaughter, and skin colour, pH, and texture of raw fillets and sensory evaluations of cooked loins were assessed 3 days after slaughter. Skin colour showed seasonal variations, particularly when measured at slaughter, with the skin being lightest during the winter. The skin became also markedly darker after 3 days storage. The dry feed group had highest growth rates, and also highest liver content. The general trend was, however, that some differences in the parameters studied were recorded for feed groups within each sampling, but differences were not consistent between samplings. Thus, the characteristics of the cod appeared to be little influenced by the type of feed they received.     

Protease activity impacts flesh colour during post-mortem storage of farmed Atlantic halibut (Hippoglossus hippoglossus): A condition referred to as chalky halibut

In the present study, fillet colour, pH and the activities of cathepsin B, B + L, D, H, collagenase and calpain were measured in 50 Atlantic halibut (Hippoglossus hippoglossus) farmed and harvested at Mørkvedbukta research station (Bodø University College) in May, 2009. May is a period of the year when a portion of the fish can temporarily lose its translucent colour, becoming milky instead, a phenomena referred to as chalky halibut. The aim of the present study was to discover whether enzymes, known to be involved in flesh quality degradation, are also involved in the post-mortem discoloration of halibut flesh. Colour assessment was performed using a Minolta instrument (L value) and a linear regression showed that pH had the most pronounced effect on chalkiness (r² = 0.81, p < 0.001). Of the investigated enzymes, cathepsins B and D explained 35 and 13% of the total variation, respectively (p < 0.01). In addition, an unexpected inverse relationship between chalkiness and calpain was found (r² = 0.48, p < 0.001). The present results suggest that the activity of cathepsins contributes to the development of chalkiness in Atlantic halibut.     

Estimating packaging atmosphere–temperature effects on the shelf life of cod fillets

The behaviour of the natural microflora (total bacterial count, psychrotrophic bacteria, total coliforms, and lactic acid bacteria) of fresh cod fillets packaged in air, under vacuum, in a modified atmosphere with low oxygen concentration (5%) and in a modified atmosphere with high oxygen concentration (80%) was monitored during storage at different isothermal conditions from 4 to 12 °C. The growth data of the total bacterial count and total coliforms were used to model kinetically the shelf life of the samples in order to check the effects of storage temperature and packaging atmosphere. The acceptability times were compared with the stability times to establish if the shelf lives predicted were correlated. At 4 °C, cod fillets packaged under vacuum and in a modified atmosphere with low oxygen concentration had a higher shelf life (6.00 and 5.42 days), calculated from the growth of the total bacterial count, than the samples packaged in other atmospheres (1.96 and 2.62). Kinetic modelling could be valuable for the prediction of microbial fish quality loss.     

超声波处理对湿腌猪肉腌制速度及肉质的影响

主要研究了超声功率、超声时间与间歇时间比、超声时间对湿腌猪肉腌制速度及肉质的影响。实验结果表明,超声波处理可以加速腌制液中食盐、亚硝酸盐和蔗糖向湿腌猪肉的渗透,加快腌制速度,并且增加肉的保水性,提高肉的嫩度,将蒸煮损失控制在合理范围之内。通过L9(34)正交实验得到超声波最佳处理工艺条件为超声功率300W,超声时间与间歇时间比1∶1,超声处理时间90min。     

The optimized modified atmosphere for packaging of pre-rigor filleted farmed cod (Gadus morhua) is 63 ml/100 ml oxygen and 37 ml/100 ml carbon dioxide

The optimal initial gas composition to maintain quality of modified atmosphere (MA) packaged pre-rigor filleted farmed Atlantic cod (Gadus morhua) at 0 °C was determined through sensory evaluation of raw odour and chemical, physical, and microbiological analyses. Cod packaged under gas to product ratio of 2:1 and gas mixtures according to a simplex centroid mixture design spanning the whole area from 0 to 100 ml/100 ml and in between mixes of all the three major packaging gases, CO₂, O₂ and N₂ were analysed after 7, 10 and 14 days of storage. Aerobic and psychrotrophic plate count decreased and formation of exudates increased with increasing CO₂ concentration. H₂S-producing bacteria were not present or not able to grow under the different gas mixtures. Odour scores and trimethylamine oxide content decreased and the formation of trimethylamine increased in the fish with decreasing CO₂ and O₂ levels. The weighted optimum gas mixture for MA packaging of farmed cod was determined to be 63 ml/100 ml O₂ and 37 ml/100 ml CO₂.