After the live pigs are chilled, the carcasses are rapidly cooled to reduce the carcass temperature to 0 to 4°C in 24 hours, and fresh meat is always in the range of 0 to 4°C during the subsequent segmentation, packaging, circulation, and retail sales. Call it cooling meat. Microbial contamination is an important hazard to the quality of cooled meat products. The circulation of cooled meat is currently used in large-scale vacuum packaging in processing plants. After being transported to supermarkets, it is packaged into small fresh-keeping packages.
As early as 20 or 30 years ago, developed countries began to research and promote cooling meat. Today, these countries have already possessed scientific processing and distribution technologies, as well as a sound and effective quality control system. In their supermarkets, they basically sell cooled meat. However, the Chinese people are still accustomed to buying “hot meat†that is slaughtered in the early morning and cleared in the morning and still maintains a certain temperature. At the same time, there is a large percentage of frozen meat on the market. What are the characteristics of hot meat, frozen meat and cooling meat?
1 The characteristics of cooling meat
Immediately after the assassination of blood-bleeding animals, there will be a certain amount of heat in the post-mortem rigorous process, resulting in a slight increase in the temperature of the meat compared to the live carcass. The slaughter of pigs is 40-42°C and then gradually falls to room temperature. The hot meat on the market at this time provides suitable temperature, rich nutrition, and high water activity for the production and reproduction of microorganisms. If the spoilage bacteria and pathogenic bacteria overproliferate, they will potentially cause hidden dangers of food poisoning.
At the beginning of this century, with the development of refrigeration technology, refrigeration technology was gradually applied to the processing and distribution of livestock meat, and frozen meat appeared. Frozen meat refers to the meat that is frozen and stored in an environment where the meat is kept below -18°C. The meat tissue is frozen and inhibits the growth and reproduction of microorganisms. However, during the thawing of frozen meat, ice crystals formed in the muscle cell matrix (volume becomes larger when the water freezes) will pierce the muscle cells, resulting in loss of juice, and deterioration of nutrients and flavor substances.
Cooled meat refers to the rapid cooling treatment of the livestock carcasses after slaughter strictly following the quarantine inspection system, so that carcass temperature (after the inside of the leg is the measurement point) is reduced to 0 to 4°C within 24 hours, and is processed, distributed, and retailed in the future. During the process, fresh meat in the range of 0 to 4°C is always maintained. Compared with hot meat, cooled meat is always in a cool environment. The growth and reproduction of most microorganisms is inhibited. Clostridium botulinum and Staphylococcus aureus and other pathogenic bacteria do not secrete toxins and can ensure the safety and health of meat. In addition, the cooled meat experienced a more complete process of thawing and ripening. The texture is soft and elastic, and the taste is delicious. Compared to frozen meat, cooled meat has the advantages of reduced juice loss and high nutritional value.
In summary, cooling meat has the advantages of safety and hygiene, delicious taste, delicate taste, and high nutritional value. The consumption of cooling meat is bound to become a trend, which is also an important symbol of a country's dietary culture. In today's global economic integration, studying the advanced technologies of developed countries and rapidly popularizing and popularizing cooling meat is a top priority for our meat science and technology workers.
2 Changes of muscle tissue after slaughter
2.1 The maturation of meat
The pig carcasses that had just been slaughtered stopped due to the supply of oxygen inside the muscle tissue, and anaerobic glycolysis of muscles replaced aerobic respiratory metabolism. Glycolytic glycolysis produces lactic acid, ATP degrades to ADP and releases energy, causing contraction of myosin and actin into actomyosin. However, because 1 molecule of glycogen produces only 3 molecules of ATP (39 molecules of ATP under aerobic conditions) under anaerobic conditions, the amount of ATP decreases dramatically and muscle contraction cannot be relieved. This phenomenon is called postmortem rigidity. At the same time, due to the accumulation of lactic acid, the pH of the meat gradually decreases. Under normal circumstances, the pH of the pork can be reduced to 5.8 within 24 hours after slaughter. At the condition of 2～4°C, after 1 to 2 days after the death, the stiffening stage ended, actomyosin dissociated into myosin and actin, and the texture of the meat gradually became soft, under the autolysis effect of the tissue inherent enzymes, the meat The flavor is better and the tenderness is improved. This process is called meat maturation.
2.2 Effect of Microbes on Meat
The contamination of microorganisms is unavoidable. Its growth and reproduction not only seriously deteriorates the organoleptic properties of meat, such as color, smell, and texture, but also destroys the nutrients of meat. The reason for cooling the post-mortem carcass is to prevent the microorganisms from excessively proliferating in the meat tissue and thus pose a hazard to the health of the consumers, while ensuring that the muscle tissue is completely frozen, autolyzed and matured.
Sichuan Soper Science & Technilogy Co., Ltd , https://www.Soper.com.cn