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.     

Double freezing of cod fillets: Influence on sensory,physical and chemical attributes of battered and breaded fillet portions

Fillet samples were processed on board a research vessel from cod (Gadus morhua) in different states of rigor mortis. In addition, headed and gutted fish in different states of rigor were frozen and, after ten days of frozen storage, the fish were thawed, processed into fillets and refrozen. During subsequent frozen storage at –24°C of breaded and battered portions processed from the different fillet batches several quality attributes were tested using sensory, physical, and chemical methods. The measurements indicated differences in the quality attributes depending on refreezing and rigor states. Especially the sensory texture attributes gumminess and, with some restrictions, firmness were found to be suitable for distinguishing single frozen (SF) from double frozen (DF) samples. This finding was supported by the outcome of the measurement of penetration force where generally a significantly (p < 0.05) higher force was necessary to penetrate the DF compared to SF samples. DF samples were generally lighter (higher L*) than SF samples. The colour difference δE between both sample types was at least very clear and therefore visible. However, no clear differences between SF and DF samples were found when evaluating the flavour attributes and using instrumental texture profile analysis for texture characterisation. Also, all chemical parameters measured did not allow to clearly distinguish between single and double frozen samples. Therefore, it can be stated that, at least when using cod as raw material for processing battered and breaded portions, the different methods for preparing the fillet blocks will, if at all, only affect the textural quality of the final products.     

不同抗老化剂对鲜湿米线品质及储藏稳定性的影响

鲜湿米线作为我国受众广泛的一种传统主食,市场前景广阔,然而其贮藏期间易于回生劣变,严重制约了米线行业的发展。本文探究了茶多酚、赤藓糖醇、海带多糖、蔗糖脂肪酸酯、焦糊精五种不同类型的抗老化剂对鲜湿米线品质及贮藏稳定性的影响。实验表明：蔗糖脂肪酸酯使米线的硬度、断条率迅速增加;茶多酚严重改变了米线的色泽及风味,而其他三种抗老化剂对鲜湿米线的理化及感官品质无显著影响。贮藏期间,海带多糖对于鲜湿米线的老化无显著影响,赤藓糖醇和焦糊精可显著提升鲜湿米线的贮藏稳定性,当贮藏时间为35天时,对照组的蒸煮损失增加了31.13%,断条率增加了20.19%,硬度增加了50.16%,短程有序度增加了7.25%,相对结晶度增加了14.69%,添加赤藓糖醇和焦糊精分别使蒸煮损失增加15.43%、15.01%,断条率增加了16.44%和15.24%,数据表明赤藓糖醇和焦糊精可以改善米线的蒸煮品质;硬度增加了13.06%和18.57%,短程有序度增加了4.91%和5.36%,相对结晶度增加了13.31%和13.29%,数据表明赤藓糖醇和焦糊精可以有效抑制米线的长期回生。综合考虑,赤藓糖醇和焦糊精适合作为专用抗老化剂应用于鲜湿米线的制作。     

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.     

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.     

Effects of perimortem stress on farmed Atlantic cod product quality: a baseline study

The potential effects of handling stress on the product quality of farmed Atlantic cod were studied in a controlled experiment (fish anesthetized with metomidate or isoeugenol, or subjected to stress by chasing for 30 min). For comparison, stress and fillet quality was also studied for commercially slaughtered farmed cod (fish sampled from waiting cage, after pumping and stunning with carbon dioxide, and after bleeding and chilling). Baseline values for stress-related parameters (blood chemistry, muscle high-energy phosphates and inosine monophospate, initial pH, muscle twitches, and rigor mortis) of rested Atlantic cod have been established. Since our stress bout showed that this species was not easily excitable, we were less convinced that we actually did study the other extreme, namely, exhausted fish. Nevertheless, the present data from the commercial slaughter of cod suggested that our stress bout was of adequate magnitude to represent potential poor handling routines. Our results consistently showed largely no differences between treatments, and that perimortem handling stress did not cause inferior flesh quality. This suggested that farmed cod can be processed with little risk of reducing product quality (quality index, fillet water content, water-holding capacity, ultimate pH, adenosine triphosphate-related degradation products and K-value, skin and fillet color, water and salt-soluble proteins, hardness, and gaping). For better maintenance of skin appearance after storage, the importance of storing the gutted cod on the belly, avoiding direct contact between skin and crushed ice, is demonstrated.     

Influence of transport and storage conditions on beer quality and flavour stability

Breweries are exporting their brands overseas, resulting in an increasingly competitive and globalised beer market. Inevitably, the beer experiences varying and prolonged periods of transport and storage prior to consumption. During this process, the flavour of fresh beer deteriorates, leading to the presence of stale flavours and a decrease in the drinkability of the beer. Results reported here show that an increased temperature during beer transport and storage causes significant flavour deterioration, as determined analytically (increase in aldehydes, beer colour and haze formation, decrease in iso‐α‐acids concentration) and sensorially (increase in overall aging score). Further, laboratory experiments show that the vibration of beer results in a rapid decrease of oxygen. Moreover, inappropriate storage temperature has a negative effect on beer quality and stability, in particular when combined with vibration. © 2018 The Institute of Brewing & Distilling     

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%.     

Process control of lightly salted wild and farmed Atlantic cod (Gadus morhua) by brine injection, brining, and freezing--a low field NMR study

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. Practical Application: Optimal processing of lightly salted cod products is important to the fish industry, due to an increasing market for this product in southern Europe. Farmed cod, which is seen as a potential steady raw material source for this production, differs considerably from its wild counterparts by having other chemical and physical muscle properties, such as lower water content and lower pH. With the processing procedures used today the farmed cod can, therefore, only be used in some of the products, where wild cod is currently used as raw material. It is, therefore, important that the processing of these products is optimized with regard to these differences in the raw material. This study gives a valuable contribution to further studies about optimal combinations of brine injections, brining, and freezing of pre- and postrigor processed farmed compared to wild cod.     

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.     

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.     

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.