In late 2012 Jinan Ourfuture Refrigeration Equipment Co., Ltd successfully accomplished the final installation and commissioning of a -55℃ tuna fish cold storage in Weihai city, Shandong province of China. We use Taiwan Fusheng brand two stage low temperature screw type parallel compressor racks. This means we have became the first company in China who successfully delivered 10,000 tons level super low temperature compressor racks for cold room chamber.
Tuna fish is ocean fish, doesn’t have inland pollution affection, the fresh tuna fish meat is very tasty and contains lots of nutrition that do good to human body. To deliver the best tuna fish quality, it requires a frozen temperature of -60℃, the long time storage temperature is -50℃~-55℃. High quality tuna fish must have good freshness and remain it’s special fresh red color. In the fishing process, other than careful pre-treatment on vessel, must pay special attention to the fast frozen process, the work is pretty complex, first we need to know some basic information:
1. Must use -60℃ super low temperature for fast frozen
When the tuna fish frozen process started, the water inside a fish cell started to crystallize at -1.5℃, till -60℃ all the water inside the cell will be completely. So the eutectic point of tuna fish is -60℃, meaning when the temperature is -60℃, the tuna fish can be fully frozen, the tuna cell function is completely stopped, so that the tuna can remain fresh for long period. If the temperature doesn’t drop to -60℃, part of the tuna cell will not be frozen and will go bad, under long term storage, this will make the fish turn black. Usually in China, from tuna harvest to it’s finally consumed, it takes around a half year, so, in order to keep the freshness, the frozen temperature must reach to -60℃, in this kind of environment, the fish can be maintained from one and a half year to two years.
2. Must use super fast frozen technology
When the frozen process started, from -1.5℃ to -5.5℃ the frozen water crystal inside a cell has the largest volume and this will easily damage the cell. If the cell is broken, when we thaw the fish, water will leak from fish cells, take away the special tuna taste, low the quality. So in order to remain the tuna fish quality, we should use fast frozen technology, reduce the frozen time especially the time the tuna fish is under -1.5℃ to -5.5℃. Reduce the fast frozen time is the key of frozen tuna fish.
Here are something suggestions:
1) Low the blast freezer temperature as much as possible, when blast freezer temperature is -60℃, the time to pass the “-1.5℃ to -5.5℃” is around 3~4 hours, but if the blast freezer temperature is -30℃, this process will take around 8~9 hours.
2) Enlarge the heat exchange rate of fish body surface. This heat exchange rate is decided by the ventilation speed of fish body surface. So under normal circumstance, the wind around the fish body will take away 90% heat from the fish, however, the frozen tray under the fish can only take away 10%.
Written and edited by mike, for more info please follow @ldmichael on twitter
Jinan Ourfuture Refrigeration Equipment Co., Ltd.
mike@refrigerationcompressorunit.com
“Our future, refrigeration future!”
"Jinan Ourfuture Refrigeration Equipment Co., Ltd is one of the leading cold room compressor rack manufacturer in China, mainly produce parallel compressor racks, condensing unit, cold room solution, walk-in freezer, food display cabinet and refrigeration retrofit products, We serve our customers with advanced technology and excellent service."
Company introduction on Youtube: https://youtu.be/XvOgRekZbns
