Freezing fish with nitrogen pays off in quality and efficiency.
Last year, for example, Pacific commissioned Airco Gases of Murray Hill, N.J., to install a nitrogen spiral freezer at its Warrenton, Ore., plant. By replacing mechanical blast freezers at Warrenton with a liquid nitrogen system, Pacific was able to improve the quality of its frozen fish and the efficiency of its plant in terms of freezing times and maintenance.
Althoguh Airco originally provided help in developing a freezing method for the dungeness variety of crab found on the U.S> West Coast, The Pacific Group has found nitrogen freezing to be superior with all of its fish products including several types of fillets and shrimp. "One of the reasons we opted for nitrogen freezing was its versatility and the fact that it could be used on all products," says Whitey Forsman, vice president and general manager at Pacific Coast Seafood, a subsidiaryy of The Pacific Group.
Crab is traditionally frozen either with a blast freezer or in salt brine. Both of these methods require significantly mor etime than nitrogen freezing, and there is some concern brine freezing can lead to the growth of listeria monocytogenes bacteria in crab.
In a blast freezer, a blast of super cooled air is passed over crab that has been precooked and cooled off with water. The temperature of a blast freezer does not fall below -40 [degrees] F, whereas a nitrogen freezer easily maintains a -100 [degrees] temperature.
Brine freezers involve placing precooked crab in water with high concentration of salt and reducing the temperature of 0 [degrees] F temperature.
Brine freezers involve placing precooked crab in water with high concentration of salt and reducing the temperature to 0 [degrees] F using mechanical refrigeration. Brine freezers not only are slower to freeze crab than blast freezers, but they leave the crab tasting salty which several consumers, especially thos in Japan, do not like.
Airco's standard liquid nitrogen freezer (Model KFS 21-300) operates by injecting liquid nitrogen into a box filled with either precooked or raw seafood. The liquid nitrogen vaporizes and fans swirl the supercold nitrogen around the fish. Using the nitrogen freezing system, Pacific Seafood was able to rduce by mor ethan half the freezing time for whole dungeness crab from 1 hour and 20 minutes to about 30 minutes.
Because nitrogen is inert and nontoxic, the flavor of the product is unaffected. Moreover, the faster a fish is frozen, the more its natural flavor and consistency is preserved. Upon thawing, nitrogen-frozen fish looks much fresher than blast-frozen fish; it shows little droop and it does not hav e a river of fish-smelling water draining off.
Pacific Coast has seen improved product quality since it began using nitrogen freezing at Warrenton, and the company is considering installing nitrogen freezers at tis other plants at Charleston and Newport, Ore.; Westport, Wash.; and Eureka, Calif.
At Warrenton, shrimp and crab are precooked before being frozen and the fillets are frozen raw. After freezing, these products are packaged in poly bags which are placed inside of cartons. The palletized cartons are then stored in a holding freezer until shipping.
In a calculated move, Pacific Coast removed its mechanical blast freezer from Warreton so Airco could install the nitrogen freezer. The freezer exchange took place without disrupting production, and the nitrogen freezer was used throughout the crab season from December 1 through April 30 last year as well as being used this year.
The nitrogen freezer is supplied with liquid nitrogen from a 9,000 gallon horizontal tank at Warrenton. The liquid nitrogen is transported to Warrenton via tanker from Airco's new air separation plant at Vancouver, Wash. In the course of freezing roughly half of its catch between December and September, Pacific Coast sued approximately 40 million standard cubic feet of nitrogen, or 80 truckloads of product.
Airco is the first company in more than 10 years to expand atmospheric gas capacity in the Northwest U.S. The company has added an 80 tons-per-day (tpd) air separation unit along with a 180 tpd liquefier that doubles Vancouver's liquid oxygen capacity to 155 tpd and triples liquid nitrogen capacity to 285 tpd. Airco built the new facility to ensure product supply reliability in the growing Northwest market.
In answering nitrogen supply concerns, Airco has eliminated all strong possible drawbacks of nitrogen freezing. The nitrogen spiral freezer is compact, ranging in size from 64 to 400-square feet of floor space. I has a microprocessor-controlled exhaust system to ensure constant operating temperatures. The exhaust system is active when nitrogen refrigerant is injected into the freezer and turned off when nitrogen injection stops. As a result, little refrigerant is pulled out of the freezer during operation and freezing efficiency is improved.
Personnel at Pacific Coast were quickly trained to operate the nitrogen spiral freezer by Airco engineers. They report that plant downtime has been greately reduced and safety has been increased since nitrogen freezing was introduced. "We are continuing to work on ways to cut production costs and improve quality," says Dulcich, "and nitrogen freezing has given us and advantage."
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|Publication:||Frozen Food Digest|
|Date:||Jul 1, 1992|
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