Pork is the main source of meat for our people and it is rich in nutrients. However, if stored at room temperature for too long, it will be contaminated by microorganisms and cause various changes, resulting in corruption. In order to prevent the contamination and corruption of meat, it is first necessary to inhibit the growth of microorganisms or to kill microorganisms. At the same time, in order to store better, it is also necessary to perform various methods for the treatment of meat, and appropriately change its nature. Therefore, storage and processing actually have the same principle and effect. There are many storage methods for meat and meat products. The traditional methods include drying method, salting method, smoke-curing method, etc.; modern storage methods include low-temperature refrigeration method, pot-storage method, irradiation treatment method, and chemical preservation method. Here are some commonly used methods. (1) Drying method. Also known as dehydration, it mainly reduces the moisture in the meat, hinders the growth and development of microorganisms and achieves the purpose of storage. The growth and reproduction of various microorganisms require the most suitable water content. Generally, at least 40-50% of water is required. Without proper moisture content, microorganisms cannot grow. The moisture content of pork is generally above 70%, and appropriate methods should be adopted to reduce the moisture content to less than 20% or to reduce the water activity in order to prolong the storage period. 1 natural air dry method: According to the requirements of the meat cuts, hang in a ventilated place, dry naturally, so that the moisture content decreases. For example, products such as dried meat, sausages, and chickens must be air-dried and dried. 2 Dehydration drying method: When processing dried meat, floss and other products, often use baking methods to remove the moisture in the meat, so that the water content dropped to 20% or less, can be stored for a longer time. 3 Add solute method: that is, add salt, sugar and other solute in meat, such as processing ham, cured meat and other products, the need to use salt, sugar, etc. on the meat marinated, the result can reduce the water activity in the meat, so that Inhibit the growth of emblem organisms. (2) salting method. The storage effect of the salt-preservation method is mainly to increase the osmotic pressure of meat through salt, to remove part of the water, and to reduce the oxygen content in the meat, resulting in environmental conditions that are not conducive to bacterial growth and reproduction. However, some bacteria have strong salt tolerance, and salting alone cannot achieve long-term preservation. Therefore, the use of salt in production is mostly carried out at low temperatures, and salting and drying methods are often used in combination to produce various flavors of meat products. (3) Low-temperature storage method. The refrigerated meat, carried in a cold store or refrigerator, is the most practical method for storing meat and meat products. Under low temperature conditions, especially when the temperature drops below -10°C, the moisture in the meat forms ice, causing the environment in which the bacteria cannot grow. But when the meat is thawed and rejuvenated, the bacteria begin to grow again due to the increase in temperature and the oozing of gravy. Therefore, when using low-temperature storage of meat, it must maintain a certain low temperature until it is consumed or processed, otherwise it cannot guarantee the quality of meat. Refrigeration of meat can be divided into cooling meat and frozen meat. 1 cooling meat: Mainly used for short-term storage of meat, usually to reduce the meat center temperature to 0 - a - 1 °C. The specific requirement is that before the meat is placed in the cold storage, the temperature of the stock is first reduced to about -4°C, and after the meat is put into storage, it is maintained between -1 and 0°C. Pork cooling time is 24 hours and can be stored for 5-7 days. The cooled meat forms a dry film on the surface, which prevents the growth of bacteria, slows the evaporation of water and extends the preservation time. 2 Frozen meat: The meat is quickly and deeply frozen, and most of the water in the meat is frozen to ice. This meat is called frozen meat. Frozen meat is more resistant to storage than cooling meat. Frozen meat is generally -23 °C below the temperature, and stored at about -18 °C. In order to improve the quality of frozen meat, it will restore its original flavor and nutritional value after thawing. At present, most cold storages adopt the quick freezing method, which means that the meat is quickly frozen at -40°C, so that the meat temperature can be quickly reduced to -18°C. Then move into the refrigerator. The cooling and freezing of meat is carried out under hanging conditions, which occupy a large number of places. For longer storage, frozen meat can be stored in a freezer storage. The temperature of the refrigerator requires less than -18°C, and the center temperature of the meat is kept below -15°C. The colder the temperature, the longer the storage time. At -18 °C, pork can be stored for 4 months; at -30 °C, it can be stored for more than 10 months. The cold storage of stored meat should meet the hygienic requirements, and each batch of products should be cleaned and disinfected prior to storage. When storing, different meat products must be stored in isolation to prevent cross-taste and affect quality. (4) Irradiation preservation method. Irradiating foods with radiation can kill bacteria on the surface and inside and achieve long-term preservation. Since the radiation preservation is to sterilize without increasing the temperature, it is beneficial to maintain the freshness of the meat, and it is free from the freezing and thawing process. It is the most advanced food preservation method. The radiation sources currently used in research in China are mainly gamma rays emitted from isotopes 60 cobalt and 137 cesium. Preservation by irradiation requires special equipment and conditions.
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