Salmon slaughtered by standard routines (control) or stressed by confinement for 10 min before stunning and then stored at 0.4 or 3.3°C for 9 days were compared. Handling stress led to lower muscle phosphocreatine (p<0.001), adenosine-5′-triphosphate (p<0.05) and shorter pre-rigor period. Storage temperature affected external quality index, white muscle pH and K-value (degradation products of ATP). Stress produced a softer fillet (p<0.001). A lower breaking strength (p<0.01) was found in fish stored at 0.4°C. Sensory tests distinguished the control/stress groups within the 0.4°C chilling regime and the 0.4°C/3.3°C chilling groups within the control regime. Stress caused a lower score for texture (p<0.05) both at 0.4 and 3.3°C and for odor at 3.3°C in a descriptive sensory test. No detectable effects of stress or storage temperature were found on flavor or color.

Handling Stress and Storage Temperature Affect Meat Quality of Farmed-raised Atlantic Salmon (Salmo Salar)

http://bluenorth.com/home/resources/Pre-slaughter_crowding_stress_and_killing_procedures_affecting.pdf

Pre-slaughter crowding stress and killing procedures affecting quality and welfare in sea bass (Dicentrarchus labrax) and sea bream (Sparus aurata)

Rigor in Atlantic salmon as affected by crowding stress prior to chilling before slaughter

The rigor mortis development of large Atlantic salmon was evaluated at a commercial plant using a sensory method, a mechanical rigorometer and low-frequency vibrations. The fish were classified according to rigor state using a neural network. Assessments were done with fish subjected to two different levels of handling stress prior to slaughter. White muscle high-energy phosphates and inosine monophosphate were used as indices of stress showing that handling stress may be considerable during commercial slaughter. Results indicate rigor assessment should be nondestructive and classificaton of rigor state was possible using a low-frequency vibration method combined with a neural network.

Rigor Mortis assessment of Atlantic salmon (Salmo salar) and effects of stress

The world availability of fish has decreased over the last few years due to a rise in population and a positive change in consumer attitudes toward the consumption of seafood. However, only a few species of the total catch are commercially important and a major portion of it remains unused due to inherent problems related to unattractive color, flavor, texture, small size, and high fat content. Although some of these species are industrially used for fish meal manufacture, a need for the conservation and utilization of by‐catch and underutilized species for human consumption has become necessary. One possible way to utilize such fish species is through isolation of meat and the development of secondary products such as surimi and surimi‐based products, sausages, and fermented products, among others. This article discusses a number of conventional techniques, such as chilling, curing, canning, and freezing, that are used for fish processing with reference to their application for production of val...

Traditional methods to process underutilized fish species for human consumption

The development of a rigor mortis-like stiffening and the biochemical changes associated with it were investigated in tilapia (Oreochromis aureus/niloticus hybrid), a tropical freshwater species, and common carp (Cyprinus carpio), a temperate freshwater fish, during storage in ice (0°C) and at ambient temperature (22°C). Onset of stiffening in carp occurred between 16 and 17 hr after death at both temperatures but full stiffness developed much later and was a longer duration at 0°C. In tilapia, onset occurred after 7 hr at 22°C and full stiffness was established after 19 hr. However, at 0°C, tilapia experienced a cold shock reaction such that they stiffened within minutes of being placed in ice and were fully rigid within 8 hr. Resolution of stiffness in this species also occurred later at 0°C. The rate of ATP degradation was similar under both storage conditions in tilapia but more rapid at ambient temperature in carp. Although the rate of lactic acid accumulation was faster at the higher temperature in tilapia, it was not nearly so marked as for carp. Objective measurement of contractions in excised muscle fibres from trout (Salmo gairdnerii) and tilapia indicated that reducing the temperature delayed the occurrence of the contraction and reduced its intensity. It was concluded that cold shock stiffening and rigor mortis stiffening are different.

Cold shock reactions in iced tropical fish

The effect on fillet yields and quality of the cold shock reaction of tropical fish when they are iced immediately following death was investigated. Tilapia (Oreochromis moss-ambicus/niloticus hybrid) were subjected to three handling treatments: filleting immediately following death; icing the whole fish immediately following death and filleting after 3 days; ageing the fish for 6 hr at ambient temperature prior to icing and then filleting after 3 days. All fillets were stored on ice until 9 days after death. Pre-rigor filleting resulted in the highest filleting yields with the least drip loss and gaping on storage but the shortest shelf life. This was accompanied by the highest post-mortem metabolic rate. The lowest yields and highest drip loss were obtained by icing the fish immediately at death followed by filleting after 3 days. A 6-hr delay before icing gave yields and drip loss which were between these two extremes and also the slowest post-mortem metabolism. The two post-rigor filleting procedures produced fillets with increased gaping but a longer shelf life compared with pre-rigor filleting. The implications of the cold shock reaction in terms of recommended codes of practice and handling operations in tropical fisheries are discussed.

N. S. D. Jones

Papers

Cold shock reactions in iced tropical fish

Effect of handling treatment on fillet yields and quality of tropical fish