Refrigeration Applications in Food Workers

  The food industry is the life industry of human beings. It is an evergreen industry that will never fail. It is a big industry related to the national economy and people's livelihood and related to agriculture, industry, and circulation. It is of positive strategic significance to increase the added value of agricultural products, to increase farmers' income, to alleviate the "three agricultural" problems, and to improve the international competitiveness of my country's agriculture. At the same time, the food industry is directly related to people's quality of life, and its modernization level has become one of the important symbols reflecting people's living standards and the level of national economic development. With the rapid growth of the national economy and the improvement of people's living standards, people's diet structure has also undergone great changes. Food consumption has changed from simply pursuing quantity to pursuing quality, nutrition, convenience, safety  and variety. Change; the consumer awareness of quality excellent brands has gradually increased, and the demand for highly processed foods has gradually increased. The frozen and refrigerated food industry is an emerging food industry that has emerged with the development of the social economy. At present, the industry has developed into a large-scale food manufacturing industry with diverse varieties and is an important part of the modern food industry. Frozen and refrigerated foods have become an indispensable part of people's modern dietary life, and are increasingly becoming one of the mainstream foods. At the same time, the frozen and refrigerated food industry has become the main industry in the economic development of some regions, and has played an important role in promoting the deep processing of agricultural products, realizing agricultural production and transformation, and solving the "three rural" problems.

  Food freezing is increasingly used around the world as an industrial-scale method of food preservation. The mechanism of food freezing and refrigeration is first: at low temperatures below 0 °C, the life activities of microorganisms are inhibited by ming'x, thereby preventing food spoilage. Second, all reactions, such as enzymatic reactions and oxidation reactions that affect food quality, are significantly reduced at low temperatures. In addition, the formation of frozen crystals in the product is also the reduction of the activity of microorganisms and the activity of water in the metamorphic reaction.

  The so-called quick-freezing is to quickly freeze the core temperature of the food to -1°C to -5°C, and the time required to pass through the maximum ice crystal formation zone does not exceed 30 minutes. For foods with high moisture content such as fresh fish and livestock meat, when the product temperature reaches -1°C, the moisture in the food begins to freeze, and when the temperature drops to -5°C, 80% of the water content freezes. At this time, the whole food is almost frozen. Therefore, the temperature limit of 1°C to 5°C is called the maximum ice crystal formation zone. The freezing speed is defined as the quotient of the distance from the food surface to the center point divided by the time required for the temperature of the center product to decrease from -1°C to -5°C, generally expressed in cm/ h said.

  All kinds of food freezing and refrigeration technology

   (1) Quick-freezing process of fruits and vegetables

  1. Process flow

  Ingredients → pretreatment (selection, cleaning, grading, peeling, cutting) → blanching → cooling → draining → quick freezing → packaging → refrigeration → transportation and sales

  2. Operation points

  The raw materials should have excellent flavor, color, ideal texture, uniform maturity, resistance to pests and diseases, high yield, suitable for mechanical harvesting; the key to blanching is: the temperature and time of heat treatment; it should be cooled quickly after blanching , cooling is divided into water cooling and air cooling; after the raw materials are blanched and cooled, there is a certain amount of water on the surface, which must be removed, otherwise it is not conducive to rapid thawing and packaging after moving; rapid freezing requires fruit and vegetable raw materials to pass through quickly in a short time. The largest ice crystal formation zone, the core temperature of the frozen product should be below -18°C to ensure the quality; the packaging can control and prevent some deterioration of the food during storage, and can be divided into inner, middle and outer packaging; quick-frozen food is generally frozen. Save, and require the temperature to be stable. The lower the temperature, the better the quality; the low temperature should be maintained during the transportation and sales process, and the long transportation time should be controlled below -18℃, generally -15℃.

  （二）Common quick-frozen aquatic products processing process

  1. Frozen shrimp

  Inspection of raw materials→Storage of raw materials→Shrimp peeling→Acceptance→Cleaning→Soaking→Fixing→Cooling→Specification→Freezing→Ice coating→Metal detection→Packing→Refrigerated transportation

  2. Quick-frozen single lobster

  Shrimp → Selection → Cleaning → Grading → High Temperature Cooking → Low Temperature Cooling → Shelling → Single Quick Freezing → Measuring → Packaging → Refrigeration

  3. Frozen squid

  Inspection of raw materials → burial removal → washing → grading → draining → weighing → salt water fixation → plate loading → semi-finished product inspection → quick freezing → tray → ice coating → packaging → inspection → refrigeration

  4. Quick-frozen whitebait

  whitebait→rinsing→cleaning→screening→soaking→weighing→packing→adding water→quality inspection→putting into plate→quick freezing→packing→quality inspection→finished product

  5. Frozen snail meat

  Acceptance of raw materials → grading → washing → impurity removal, removal of tail intestines → full rinsing → draining water → weighing → bagging arrow sealing → freezing → packing → refrigeration

  6. Frozen oysters

   Oyster material selection → washing → soaking, spitting sand → opening the shell and taking the meat → grading, inspection → rinsing → draining → freezing → ice plating → vacuum packaging → frozen storage

  7. Frozen sea eel slices

  Acquisition and transportation → selection → live killing and bloodletting → tail cutting and bloodletting → immersion in water to remove blood → visceral removal → cleaning → ice water preservation → ice water cleaning → removal of dorsal, anal and caudal fins → deboning, head and tail → Take fish fillets → divide into specifications → rinse → plate placement → quick-freezing → weighing → ice plating → bagging → packing → refrigerating

  8. Frozen Butterfly Shellfish

   Raw materials → keep alive at low temperature → washing → breaking the shell and taking the meat → taking the axe foot → washing → opening the slices → decontamination and shaping → sorting → washing → weighing → loading on the plate → pre-cooling → quick freezing → unpacking → packaging →Finished product inspection →Refrigeration

   (3) Frozen storage technology of livestock and poultry meat

  1. Freeze method

  Still air freezing method; plate freezing; air-cooled quick freezing

  2. Freeze the process of winter storage

  1), two-stage freezing process

  The processed meat carcasses are first sent to the cooling room for cooling, and then sent to the freezing room for freezing when the temperature of the meat is cooled to 0-4°C. The temperature of the meat in the center of the leg can be lowered to -15°C after about 20-24 hours during the freezing time of the cooled meat at a room temperature of -23-25°C and an air flow rate of 2-3m/s. At present, the United States, Germany, Japan and other countries mostly use a two-stage freezing process for meat freezing.

   2), direct freezing process

& emsp; When the carcass meat accumulates to the equivalent of a freezing room, focus and quickly advance the freezing time of the storage temperature below -15 °C to freeze.

  Developing and improving my country's food refrigeration processing technology is a long way to go. It requires the cooperation of food processing industry, refrigeration equipment manufacturing industry, packaging material industry, logistics and warehousing industry, transportation industry, supermarket chain industry and other related industries to form a complete food industry. technical system, rapidly improve the production and technical level of my country's food production equipment, market-oriented, actively develop, develop, and produce all kinds of food refrigeration equipment with international advanced level, in order to further modernize the food cold chain equipment and achieve international In line. At present, among the technologies and equipment announced in foreign food freezing and refrigeration industries, their footprints can be found in my country, but we have to admit that many new technologies and new equipment are mostly imported or transplanted from abroad. The harsh reality Tell us that strategic technologies and core technologies cannot be introduced, and we can only make up our minds to go our own way. In order to improve the original innovation ability of my country's food freezing and refrigeration industry, we should not only focus on individual technological innovation, but also pay attention to the integration of various innovations.