Research

Causes and Prevention of Bruising in Salmon

Problem:

Bruising is a serious quality defect for Alaska salmon responsible for significant opportunity and monetary loss each year. Using techniques from the vegetable industry, the impact force and duration, primary causes of bruises, will be quantified. Extrinsic factors such as product temperature, physiological condition and rigor will be evaluated for their contribution to the bruising process. Actual conditions existing in fishing and processing operations will be determined and strategies for bruise control and/or reduction will be developed. The cost of bruised salmon to the Alaska seafood industry is considerable. One processor was unable to use 75% of three vanloads of sockeye salmon as fillets due to bruising (Kelley, 2002).

Approach:

Using methods and instruments developed in the vegetable industry, this proposal seeks to understand the forces responsible for bruises in Alaska salmon, evaluate handling and processing methods to identify problems areas and to suggest solutions to reducing these bruises. The objective of this project was to determine the impact forces and duration required to produce bruises in Alaska salmon. In addition, we will evaluate intrinsic and extrinsic factors that influence bruise development as well as commercial handling and processing methods to identify where bruises are likely to occur. Finally we will develop strategies for bruise reduction and/or control. The information will be disseminated through the agency of the Alaska Marine Advisory Program.

Results:

Impact recording devices (IRDs) were used to determine the forces required to bruise fresh salmon. A series of pilot plant tests showed that impacts of 1.2 kg and velocities as low as 0.06 m/sec resulted in noticeable capillary bruising in pink salmon. Higher impacts of 3.4 kg resulted in moderate internal bruising along the tail and backbone. These forces translated to dropping a fish onto a hard surface from as little as 0.5 m. The force applied by picking a fish up by the tail could be as high as 6.2 kg. These devices were subsequently used in a local seafood processing plant to measure velocities and forces in the processing equipment. Movement along conveyors and short drops (<0.15 m) rarely exceeded values responsible for bruising. However, the hand sorting process and throwing the fish into totes or sliding them into RSW tanks exceeded these forces 72% of the time.

Contact person:

Dr. Scott Smiley: stsmiley@alaska.edu