Liquid nitrogen is a colorless, tasteless, low viscosity transparent liquid, chemically stable, does not combine with any substance. Liquid nitrogen, as the largest product of air liquefaction separation and the by-product of industrial oxygen production, has been attached great importance to and recognized by the unique properties of liquid nitrogen. The application of liquid nitrogen as an ideal refrigerant in the food industry, especially in the application of food freezing, has made great progress in the world. It has been hailed as one of the most outstanding achievements of the food industry in twentieth Century. In our country, the application of liquid nitrogen in various aspects of food industry has gradually arisen, but there are still many problems. With the increasing demand for food, nutrition and food safety, and has become the leading technology, as a part of liquid nitrogen cryogenic technology family in food, instead of the traditional processing methods, in the field of food industry will have better development.

1. quick freezing speed (faster than the general freezing freezing method about 30-40 times faster): the frozen food can be made quickly, by 0 to 5 DEG C maximum crystal zone, has food researchers made a useful attempt in this field.

2., to maintain food quality: because liquid nitrogen quick freezing time is short, the liquid nitrogen quick-frozen food can be the limit.

Maintain color, aroma, taste and nutritional value before processing. Duan Zhenhua, [3], et al. Treated areca with liquid nitrogen for quick freezing. The result showed that areca treated with liquid nitrogen had higher chlorophyll content and good flavor.

3. material dry consumption is small: the average dry loss rate of freezing is 3 to 6%, while liquid nitrogen quick freezing can be reduced to 0.25 ~ O.5%.

4., equipment and power costs are low, easy to achieve mechanized and automated assembly line, improve productivity.  

5. at present, liquid nitrogen freezing mainly consists of three kinds of spray freezing, dipping freezing and cold air freezing. Among them, spray freezing is the most widely used.

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