Deciphering why liquid nitrogen quick freezing is so popular
2020-07-31 14:32:48
With the further improvement and development of liquid nitrogen quick freezing technology, liquid nitrogen quick freezing is quickly and widely used in fish, shrimp, crabs, chicken, duck, meat (cattle, sheep, etc.), fruits (bayberry, lychee, etc.), vegetables, and All kinds of prepared foods (steak, sashimi, meatballs, fried shrimp, patties, hamburgers, pizzas, egg products, soups, etc.) are frozen. In the UK in 1981, liquid nitrogen quick-frozen food accounted for 10% of frozen food, and the amount of liquid nitrogen used exceeded 100kt. 1/3 of the production of liquid nitrogen in Western Europe is used for quick freezing and refrigerated transportation of food. Japanese liquid nitrogen quick-frozen food accounts for about 40-50% of frozen food. At present, hundreds of food processing companies in the United States use liquid nitrogen for quick freezing, and only one quick-frozen steak plant uses 700t of liquid nitrogen per day. In the early 1970s, Beijing and Shanghai had developed liquid nitrogen quick-frozen food production lines. In the 1980s, various quick-freezing devices (including liquid nitrogen quick-freezing) were introduced from Japan, Sweden, France, the United States, and Denmark. Fresh aquatic products such as lake crabs and prawns are quick frozen with liquid nitrogen. Because each kilogram of quick-frozen food requires 0.8-1kg of liquid nitrogen, affected by the high price of liquid nitrogen, in 1991, among the 250 various kinds of quick-freezing devices manufactured by our country, very few of them used liquid nitrogen. The proportion of frozen food is very low, and it has not been widely used.
Liquid nitrogen is a colorless, odorless, low-viscosity transparent liquid with stable chemical properties. The boiling point of liquid nitrogen under normal pressure is -195.8°C. When it comes into contact with frozen food, the latent heat of evaporation that can be absorbed is 198.9kJ/kg; then the nitrogen vapor is heated to -20°C, and the average specific heat is 1.047kJ /(Kg·K), it can absorb 184.1kJ/kg. The total of the two items is 383.0kJ/kg, which is an ideal refrigerant. Quick-freezing food with liquid nitrogen started in the United States. The United States began research in this area in the 1950s, and it was officially used in quick-frozen food in 1960. It was quickly promoted in production in 1964.
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