One of the projects that is being worked on in Matís' Processing and Product Development Division is called Refrigeration. Its aim is to promote the implementation of best knowledge and procedures for refrigeration and process control for fish products to ensure quality properties, traceability and safety of raw materials and products, and to promote the utilization of this information for Icelandic producers in their markets.
It is known that rapid and safe cooling of marine catches maintains better quality, prolongs shelf life and thereby increases the value of marine products. In recent decades, increasing attention has been paid to liquid and pumpable ice media, which are commonly referred to as slush or liquid ice. It is a mixture of liquid (water, salt water or sea) and ice crystals with a particle size of approx. 0.005 - 1 mm. Due to the salt content, the freezing point of sludge and liquid ice is lower than 0 ° C, which contributes to faster cooling than with conventional flake ice, as has often been shown experimentally.
In the project, comparative experiments were performed on cooling rate and cooling capacity (how well the refrigerant maintains cooling) of different types of pumpable ice media and flake ice. The different refrigerants used in the experiments were as follows: uncooked flake ice, crushed flake ice, liquid ice from Optimar ("Optim-Ice"), slush ice from Skagan ("Flow-Ice"), liquid ice from Crytec ("Bubble Slurry Ice") ) and saline. The ambient temperature was closely monitored and therefore controlled in the experiments to minimize its potential impact. The development of the temperature of saithe in both refrigeration and storage was monitored, in addition to which a cylinder of agar nutrient was cooled in different ice media.
The main results of the experiments are that the temperature of the refrigerant is most important for the cooling rate. The importance of even distribution of the refrigerant was abundantly clear, but the particle size of liquid / slush ice is not as important a property. Based on the temperature measurements made in the project, flake ice seems to be more suitable than liquid ice for storing fish, provided that the storage is longer than approx. 3 days.
Graph showing different cooling rates (pdf file)
The project was funded by the Rannís Technology Development Fund and AVS.