Application of liquid nitrogen in food industry

1. Application of liquid nitrogen in food quick-freezing

        Among the numerous collection methods, the frozen collection method is the most widely used, and the results are also very obvious. Liquid nitrogen quick-freezing, one of the methods of freezing and storage, has long been accepted by food processing enterprises. Because it can realize ultra-quick freezing at low temperature and deep freezing, it is also conducive to the partial vitrification of frozen food, so that the food can recover to the greatest extent after thawing. To the original strange state and original nutritional content, the quality of frozen food has been greatly improved, so it has shown unique vitality in the quick-freezing industry. Compared with other freezing methods, liquid nitrogen quick freezing has the following obvious advantages:

        ① Fast freezing rate (the freezing rate is about 30-40 times faster than the usual freezing method): Quick freezing with liquid nitrogen can make the food quickly pass through the maximum ice crystal growth zone of 0°C to 5°C. Food researchers have done useful work in this regard. experiment of.

        ②Maintain the quality of food: Due to the short freezing time of liquid nitrogen, the food that is quick-frozen in liquid nitrogen can maximize the color, aroma, taste and nutritional value before processing. Duan Zhenhua and others used liquid nitrogen to quickly freeze betel nut, and found that the betel nut treated with liquid nitrogen continued to have higher chlorophyll content and good charm.

        ③ Small dry consumption of materials: the dry consumption loss rate of normal freezing is 3-6%, while liquid nitrogen quick-freezing can be reduced to 0.25-0.5%.

        ④The equipment deployment and power consumption are low, and it is easy to realize the mechanization and automation of the assembly line, and improve the productivity.

At present, liquid nitrogen quick freezing mainly includes three methods: spray freezing, immersion freezing and cold atmosphere freezing, among which spray freezing is the most widely used.

        2. Application of liquid nitrogen in beverage processing

        At present, many beverage manufacturers have adopted nitrogen or a mixture of nitrogen and C02 to replace the traditional C02, and gas-filled beverages. Nitrogen-filled, highly carbonated beverages cause fewer problems than carbonated-only beverages; nitrogen is also ideal for canned still beverages, such as wine and juice. The benefit of filling non-carbonated beverage cans with liquid nitrogen is that the small amount of liquid nitrogen injected removes oxygen from the headspace of each can, rendering the gas in the upper space of the tank inert, extending the shelf life of perishables .

        3. Application of liquid nitrogen in the storage and preservation of fruits and vegetables

        The use of liquid nitrogen for the storage and preservation of fruits and vegetables has the advantage of controlled atmosphere, which can adjust the contradiction between the supply and demand of agricultural and sideline products in the peak season and the off-season, and eliminate the loss in storage. The function of modified atmosphere is to increase the concentration of nitrogen, and at the same time control the gas ratio of nitrogen, oxygen and C02, and keep it in a stable state, reduce the respiration intensity of fruits and vegetables, and delay the post-ripening process, so that fruits and vegetables remain strange when picking. state and original nutritional value, extending the preservation period of fruits and vegetables.

        4. Application of liquid nitrogen in the processing of finished meat products

        The addition of liquid nitrogen in the processes such as mincing, chopping or mixing of the meat can effectively improve the quality of the product. For example, in the processing of salami-type sausages, the use of liquid nitrogen can improve the water retention of meat, prevent fat oxidation, and improve slicing and surface quality; it is used in the processing of processed meat such as meat snacks and dried meat, which can not only confuse the minced meat. It can speed up protein dissolution and enhance water retention, and is especially useful for linking the unique shape of the product. Other raw meats are rapidly cooled by liquid nitrogen, which can not only maintain the characteristics of hot meat in a relatively long time, but also ensure the hygiene and safety of the meat; in terms of processing technology, there is no need to worry about the impact of temperature rise on meat quality, and processing can not be affected. The influence of raw material temperature, processing time, and seasonal factors can also make the processing process at low oxygen partial pressure, which extends the shelf life of the product within a certain range.

        5. Application of liquid nitrogen in low temperature crushing of food

        Low-temperature pulverization is the process of breaking the material cooled to the embrittlement point temperature into powder under the action of external force. Low-temperature crushing of food is a new food processing technology developed in recent years. This technology is suitable for processing foods with high aromatic content, high fat content, high sugar content and high gelatinous substances. Using liquid nitrogen for low-temperature crushing treatment, the bones, skins, meat, shells, etc. of the raw materials can be crushed all at once, so that the finished particles are small and maintain their useful nutrients. For example, in Japan, seaweed, chitin, vegetables, condiments, etc., which have been frozen in liquid nitrogen, are put into a pulverizer to be pulverized, so that the fine particle size of the finished product can be as high as 100 μm or less, and the original nutritional value is basically maintained. In addition, using liquid nitrogen for low-temperature pulverization can also pulverize materials that are difficult to pulverize at room temperature, heat-sensitive and easily degraded and easy-to-analyze materials. In addition, liquid nitrogen can pulverize food materials that are difficult to pulverize at room temperature, such as fatty meat and vegetables with high water content, and can produce new processed foods that have never been seen before.

        6. Application of liquid nitrogen in food packaging

        A company in London, England, has developed a simple and practical method of food preservation, which is to add a few drops of liquid nitrogen into the packaging bag when packaging the food. When liquid nitrogen is evaporated and transformed into gas, its volume rapidly expands, quickly replacing most of the original gas in the packaging bag, eliminating the deterioration of food caused by oxidation, thereby greatly extending the preservation period of food.

        7. Application of liquid nitrogen in food refrigeration and transportation

        Refrigerated transport is an important part of the food industry. It is a common development trend in the world to develop liquid nitrogen refrigeration technology and develop liquid nitrogen refrigerated trains, refrigerated vehicles and refrigerated containers. Years of application practice in economically developed countries explain that liquid nitrogen refrigeration system is the only refrigeration and preservation technology that can compete with mechanical refrigeration systems in trade, and it is also the development direction of food refrigeration and transportation.

        8. Other applications of liquid nitrogen in the food industry

        Due to the refrigeration effect of liquid nitrogen, egg juice, liquid condiments, and soy sauce can be processed into granular frozen foods that are free-moving and pourable, which are readily available and easy to prepare. When grinding spices and water-absorbing food additives, such as sugar substitutes and lecithin, liquid nitrogen is injected into the grinder to protect valuable ingredients while also increasing grinding output. Zhou Shunhua et al. have proved that the use of liquid nitrogen quenching combined with high temperature thawing to break the pollen wall has the characteristics of good fruit yield, high wall breaking rate, fast speed, stable physiological activity of pollen, and no pollution.