Sigurjon Arason

Changes in myofibrillar proteins during processing of salted cod (Gadus morhua) as determined by electrophoresis and differential scanning calorimetry

The effects of salt-curing, drying and rehydration on muscle proteins in cod (Gadus morhua) were studied during the processing of heavily salted cod or “bacalhau”. The aim was to observe conformational stability and possible degradation or denaturation, with sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and differential scanning calorimetry (DSC). The salting process significantly decreased the heat stabilities of both myosin and actin. The decrease in water content during dry-salting did shift the transition temperatures slightly back to higher temperatures. The results, from the SDS-PAGE, showed that the myosin heavy chain (MHC) was cleaved into smaller sub fragments in the salting process with the two heavy meromyosin fractions (HMM S1 and S2) and the light meromyosin (LLM) fraction being the most abundant. Actin was less affected than myosin.

Benefits of traceability in fish supply chains – case studies

Purpose – The purpose of this paper is to investigate how the seafood industry perceives benefits of traceability implementation. Furthermore, ex ante cost‐benefit analyses (CBAs) of adopting new traceability systems are conducted for two firms, operating at different steps of the seafood supply chains, to obtain preliminary knowledge on the net benefits of the project and on how costs and benefits are distributed among the actors.Design/methodology/approach – This is a case‐based study.Findings – The surveyed companies perceive improving supply chain management as the most important benefit of traceability. Other benefits are increase of the ability to retain existing customers; product quality improvement; product differentiation; and reduction of customer complaints. However, the quantifiable benefits are perceived differently by the actors at different steps in the supply chains, e.g. implementing radio frequency identification (RFID) tags on pallets in the seafood trading company case study shows tan...

Production of fish silage

Fish material that is not for human consumption is used for the production of fishmeal which has a world market of considerable size. However, new ways of utilizing pelagic fish, fish waste and fish viscera are continuously being looked for.

Effects of Dry Ice and Superchilling on Quality and Shelf Life of Arctic Charr (Salvelinus alpinus) Fillets

The influence of different cooling techniques (dry ice/ice packs) and storage temperature (-2°C/3°C) to prolong the shelf life of Arctic charr (Salvelinus alpinus) fillets were evaluated by sensory analysis, physical methods, chemical and microbial analysis. The effects of storage temperature were stronger than of different cooling agents. Superchilling (-2°C) of fillets packed with dry ice resulted in 6 days extension of shelf life compared to chilling (3°C). The use of dry ice parallel to superchilling prolonged shelf life for 1 day compared to fillets stored with ice packs. No negative effects on quality of the fillets where detected that could be linked to cell destruction caused by partial freezing or to sour taste, caused by absorption of CO2 gas in fish flesh.

The influence of additives and drying methods on quality attributes of fish protein powder made from saithe (Pollachius virens).

BACKGROUND Fish protein powder (FPP) is used in the food industry for developing formulated food products. This study investigates the feasibility of increasing the value of saithe (Pollachius virens) by producing a functional FPP. Quality attributes of spray and freeze-dried saithe surimi containing lyoprotectants were studied. A freeze-dried saithe surimi without lyoprotectants was also prepared as a control sample. RESULTS The amount of protein, moisture, fat and carbohydrate in the FPPs were 745-928, 39-58, 21-32 and 10-151 g kg(-1). Quality attributes of FPPs were influenced by the two drying methods and lyoprotectants. The highest level of lipid oxidation was found in the control and the second highest in the spray-dried FPP. The spray-dried fish protein had the lowest viscosity among all FPPs. Gel-forming ability of samples with lyoprotectants was higher than that of the control. Water-binding capacity, emulsion properties and solubility of the freeze-dried fish protein containing lyoprotectants were significantly higher than spray-dried and control samples. However, functional properties of spray-dried FPP were higher than the control sample. CONCLUSION It is feasible to develop value-added FPP from saithe surimi using spray- and freeze-drying processes, but freeze-dried FPP containing lyoprotectant had superior functional properties and stability compared with spray-dried sample. Both products might be used as functional protein ingredients in various food systems.

Characteristics of freeze-dried fish protein isolated from saithe (Pollachius virens)

Fish proteins isolated from by-products or low commercial/underutilized species using pH-shift process is a new source of proteins that may be used as wet or dried ingredients to develop value-added convenience foods. This paper reports the effects of freeze-drying on characteristics of fish protein isolates (FPI) from saithe (Pollachius virens) with or without lyoprotectants. Freeze-dried saithe mince from the same lot and without additives was used as a control. The resulting fish protein powders contained 71-93% protein, 1.5-3% moisture, 0-21% carbohydrate and 0.5-2% fat. Lipid oxidation (assessed by TBARS) of FPI powder groups was higher than that of fish mince powder. The results revealed that oxidation started during the pH-shift process and was increased by freeze-drying. Functional properties and sensory attributes were influenced by the advanced oxidation. However, the mince powder was less oxidized and had higher functional properties such as water binding capacity, gel forming ability, emulsification, foaming properties and colour and lower sensory scores for rancid odour and flavour than the FPI powders. Further studies on how to prevent oxidation of fish flesh during pH-shift and drying processes are recommended.

Shelf life of air and modified atmosphere-packaged fresh tilapia (Oreochromis niloticus) fillets stored under chilled and superchilled conditions

Optimal packaging and storage conditions for fresh tilapia fillets were established by evaluating sensory and microbiological changes, as well as monitoring physicochemical properties. Nile tilapia (Oreochromis niloticus) farmed in recirculation aquaculture system was filleted, deskinned, and packaged in air and 50% CO2/50% N2 prior to chilling and superchilling storage at 1°C and −1°C. Sensory analysis of cooked samples revealed a shelf life of 13–15 days for air-packaged fillets during storage at 1°C and 20 days at −1°C. At the end of shelf life in air-packaged fillets, total viable counts (TVC) and pseudomonads counts reached log 8 colony-forming units (CFU) g−1. In 50% CO2/50% N2-packaged fillets, the lag phase and generation time of bacteria were extended and recorded counts were below the limit for consumption (<log 8 CFU g−1) after 23 days of storage at both 1°C and −1°C. However, modified atmosphere (MA) packaging negatively affected color characteristics of the fillets soon after packaging (day 6). Color is an important indicator of tilapia fillets quality and a major factor in influencing retail purchase decisions. In view of that, air packaged at −1°C storage temperature was the optimal condition for fresh tilapia fillets. Total volatile basic nitrogen (TVB-N) and trimethylamine (TMA) were not good indicators of spoilage of tilapia fillets in this study.

Effects of temperature during frozen storage on lipid deterioration of saithe (Pollachius virens) and hoki (Macruronus novaezelandiae) muscles

Lipid deterioration of two lean fish species, saithe (Pollachius virens) and hoki (Macruronus novaezelandiae), during frozen storage at -20 and -30°C (up to 18months) was studied. Lipid composition, lipid oxidation and hydrolysis, and sensory attributes were evaluated on both light and dark muscles of the fish species. Results showed significant lipid deterioration with extended storage time, but lower storage temperature showed significantly more preservative effects. A marked difference was observed between the composition of dark muscle of hoki and saithe. Polyunsaturated fatty acids were the predominant lipids in dark muscle of saithe, while monounsaturated fatty acids were predominant in dark muscle of hoki. Further, the hydrolytic activity differed greatly between dark muscle of hoki and saithe, with significantly lower activity observed in hoki. Present results indicate that both tertiary lipid oxidation and hydrolysis products are appropriate for assessing lipid deterioration of saithe and hoki light muscle during frozen storage.

Flavor and quality characteristics of salted and desalted cod (Gadus morhua) produced by different salting methods.

Flavor characterization and quality of salt-cured and desalted cod (Gadus morhua) products was studied using sensory analysis and gas chromatography techniques. The products were produced in Iceland using two different processing methods (filleting and splitting) and three different salting procedures, i.e., the old single-step kench salting or a multistep procedure, and presalting (injection and brine salting or only brine salting), which was followed by kench salting. The main difference observed was between fillets and split fish, where the split fish was darker and had stronger flavor characteristics. Comparison of different salting procedures showed that the use of presalting improved the appearance of the salted products, which can be described as increased lightness and reduced yellowness of the products. In the same products, the intensity of curing flavors was milder, as described by sensory analysis and key aroma compounds. Derivatives from lipid and protein degradation contribute to the characteristic flavor of the salted products.

The Effects of Presalting Methods from Injection to Pickling, on the Yields of Heavily Salted Cod (Gadus morhua)

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. Practical Application: Salting procedures for cod have changed rapidly in recent years. Injection is increasingly used as a presalting method. It has been suggested to have strong effects on weight yields of salted cod products. This article describes the effects of injection on weight yields on products in salted, rehydrated, and cooked stage.