With the further improvement and development of liquid nitrogen quick freezing technology, it is quickly and widely used in fish, shrimp, crab, chicken, duck, meat (cattle, sheep, etc.), fruits (bayberry, lychee, etc.), vegetables, and various Pre-made foods (steak, sashimi, meatballs, fried shrimp, meat patties, hamburgers, pizzas, egg products, soups, etc.) are being frozen. In the United Kingdom, liquid nitrogen quick-frozen food accounted for 10% of frozen food in 1981, 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. Quick freezing of fresh aquatic products such as lake crabs and prawns in liquid nitrogen**. Because each kilogram of quick-frozen food requires 0.8-1kg of liquid nitrogen, due to 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 quick freezing has the following advantages:
(1) Liquid nitrogen can be in close contact with all parts of food with irregular shapes, reducing the heat transfer resistance to a small limit.
(2) Liquid nitrogen is non-toxic and inert to food ingredients. Furthermore, because it replaces the air coming out of the food, it can reduce oxidation changes to a small limit during freezing and packaging storage.
(3) The quality of frozen food is high. Since liquid nitrogen is in direct contact with food, it conducts intense heat exchange with a temperature difference of more than 200K, so the freezing speed is extremely fast, and the temperature can be reduced by 7-15K per minute. The ice crystals in the food are small and uniform, and the food quality after thawing is high.
(4) The dry consumption of frozen food is small. The dry consumption rate of food frozen with general freezing device is between 3% and 6%, while the dry consumption rate is between 0.6% and 1% when freezing with liquid nitrogen freezing device. Therefore, it is suitable for freezing some foods with high moisture content, such as bayberry, tomatoes, crab meat, etc.
(5) Small footprint, low initial investment and high device efficiency.
Liquid nitrogen quick freezing has the following disadvantages:
The advantages of using liquid nitrogen to quickly freeze food are many and varied, but it also has the following problems in its current application, which need to be solved urgently:
(1) Liquid nitrogen becomes low-temperature nitrogen after evaporation, which has the ability to absorb a large amount of sensible heat. Making full use of this part of the cold capacity is the fundamental to improve the economics of liquid nitrogen refrigeration equipment, but the current utilization rate is not high and measures need to be strengthened.
Nuoruida (Tianjin) science and Technology Co., Ltd. is committed to research, development, and sales of liquid nitrogen freezer. Using European technology, we provide a variety of equipment. The main equipment is liquid nitrogen cryogenic freezer, liquid nitrogen cabinet freezer, liquid nitrogen tunnel freezer,sub-zero processing equipment, cryogenic freezing equipment, and so on.
