An overview of the storage technology of fresh meat with modified atmosphere

An overview of the storage technology of fresh meat with modified atmosphere

Modified atmosphere packaging machines are typically two to three times larger than other forms of packaging, resulting in higher logistics and storage costs. However, if a mixture of nitrogen, oxygen and carbon dioxide is used to replace the air and stored at the correct temperature, it can reduce food spoilage, maintain freshness and ensure safety, and the scientific gas ratio can make the food in a state of color saturation, which is attractive , In addition to fresh meat, modified atmosphere packaging of fresh-cut fruits and vegetables is also increasing year by year. The concept of light food is very popular now: buy a vegetable salad in modified atmosphere packaging, and get a fresh convenience, which is very important for the light food crowd. Modified atmosphere packaging is also often used for coffee beans, a boon for coffee lovers, and this packaging provides a high degree of freshness and a long shelf life. In addition, dairy products and cooked products are actively switching to modified atmosphere packaging.

1. The Development of Modified Atmosphere Preserved Meat

The first application was in the 1930s, with high concentrations of CO2 in controlled atmosphere. In 1938, 26% of fresh meat in Australia and 60% in New Zealand were transported under CO2-controlled atmosphere storage. Studies have shown that adding 20% CO2 can inhibit the reproduction of Gram-negative bacteria in meat. In the 1980s, 99% CO2 was the ideal way to keep fresh. If microbial contamination is effectively prevented from slaughtering to packaging and storage, fresh meat can be stored for 20 weeks at 0°C in modified atmosphere.

my country's research on modified atmosphere fresh-keeping meat began in the late 1980s. As a non-thermal food processing technology accepted by consumers, ultra-high pressure technology can effectively inactivate spoilage bacteria and pathogenic bacteria in food, and can maintain the original food. Some sensory properties and nutritional quality meet consumers' requirements for less food processing, food safety, high stability and less use of food additives. Modified atmosphere packaging machine technology conforms to the concept of green environmental protection, and there is no need to add chemical preservatives and stabilizers during use. As a means of preservation, it has been widely used. Especially in the application of fruit and vegetable products, it has greatly accelerated the marketization of many fruit and vegetable products. This technology is based on Chinese traditional and characteristic Chinese dishes as raw materials, and combines modern high-tech - ultra-high pressure technology with modified atmosphere packaging technology to develop ready-to-eat Chinese dishes. In addition, through tray packaging and labels with exquisite design and detailed information on products and companies, the fresh texture of food can be fully presented, the quality of products can be improved, and consumers’ sense of security and trust can be increased.

2. Changes in the color of fresh meat

Freshly slaughtered meat is purplish red. When exposed to air, it is easy to synthesize myoglobin under high oxygen, making the meat bright red. Further oxidation forms oxidized myoglobin, which darkens and browns the meat. At low oxygen partial pressure (eg in vacuum packaging), oxymyoglobin is converted to myoglobin and further to myoglobin. Under anaerobic conditions, meat can effectively prevent browning and oxidation.

3. Mechanism of Fresh Meat Preservation with Modified Atmosphere

By filling a certain amount of gas in the package, it destroys or changes the conditions that microorganisms depend on for survival, reproduction and discoloration, so as to achieve the purpose of preservation.

The gases used in modified atmosphere packaging are usually CO2, O2 and N2, or various combinations thereof. Each gas has a different effect on fresh meat preservation.

(1) CO2

CO2 has a strong inhibitory effect on the reproduction of most aerobic bacteria and molds. CO2 can also prolong the lag phase of bacterial growth and reduce the speed of its logarithmic growth phase, but has no effect on anaerobic bacteria and yeast. Since CO2 is soluble in meat, it reduces the pH value of meat, which can inhibit some acid-intolerant microorganisms. However, CO2 has high air permeability to plastic packaging films and is easily soluble in meat, which leads to the falling of packaging boxes and affects the appearance of products. Therefore, if CO2 is selected as the protective gas, packaging materials with better barrier properties should be selected.

(2) O2

It inhibits the reproduction of anaerobic bacteria when fresh meat is stored, and makes the meat bright red in a short period of time, which is easily accepted by consumers. However, the addition of oxygen greatly shortens the storage period of modified atmosphere packaged meat. At 0°C, the storage period is only 2 weeks.

(3) N2

N2 is an inert gas, which has no effect on the packaged material and will not be absorbed by the food. Nitrogen has a very low air permeability to plastic packaging materials, so it can be used as a mixed gas buffer or balance gas, and can prevent the packaging box from being crushed by atmospheric pressure due to CO2 escaping.

4. Selection of modified atmosphere gas for fresh meat

The gas used for modified atmosphere fresh-keeping meat must be a mixed gas composed of one, two or three gases in a certain proportion according to the fresh-keeping requirements.

(1) 99% pure CO2 modified atmosphere packaging

(2) Modified atmosphere packaging of 75% O2 and 25% CO2

(3) 50%O2, 25%CO2 and 25%N2 modified atmosphere packaging

Five, fresh meat modified atmosphere packaging machine should pay attention to the problems

① Handling of fresh meat before packaging

The fresh meat modified atmosphere packaging machine should pay attention to the following problems. After the pig is slaughtered, if it is cooled to 24 h at a temperature of 0~4 °C, the activity of ATP in the fresh meat can be inhibited to complete the acid excretion process. This kind of cooled meat after deacidification has far better nutrition and taste than quick-frozen meat. In order to ensure the fresh-keeping effect of modified atmosphere packaging, it is also necessary to control the hygienic indicators of fresh meat before packaging to prevent microbial contamination.

② Selection of packaging materials

Modified atmosphere packaging should use packaging materials with good barrier properties to prevent the escape of gas in the packaging and the infiltration of O2 in the atmosphere. As a modified atmosphere packaging for fresh meat, the machine requires good barrier properties to CO2 and O2. Usually, composite packaging films with PET, PP, PA, PVDC, etc. as the base material are used.

③ Guarantee of inflation and sealing quality

The control of inflation and sealing quality must rely on advanced inflatable packaging machinery and good operating quality. For example, the continuous vacuum inflatable packaging machine, from container forming, metering filling, vacuum inflation to sealing and cutting, printing date and product output, is automatically and continuously completed on one machine, which is not only reliable, but also reduces the packaging operation process. This kind of pollution is conducive to improving the preservation effect.

④Control of product storage temperature

The influence of temperature on the preservation effect is mainly reflected in: first, the temperature directly affects the activities of various microorganisms on the surface of the body; second, the barrier properties of packaging materials are closely related to temperature. The higher the temperature, the less the barrier properties of the packaging material.

Therefore, it is necessary to realize the temperature control of the whole process from product, storage, transportation to sales. Consumers like natural and fresh food. Modified atmosphere packaging (MAP) can prevent the deterioration of fresh meat and improve the product shelf image. One of the new technologies, In addition to fresh meat, all kinds of meat, fish, seafood, baked goods, dairy products, prepared foods, cooked foods, etc. can use modified atmosphere packaging to improve retail charm. Modified atmosphere packaging of food is widely used in developed western regions. With the new packaging technology, the food using modified atmosphere packaging can be kept fresh for a long time, and the original color, taste, shape and maintenance of the food can be better presented and maintained. With the rapid development of the domestic economy, consumers pay more and more attention to the freshness, safety and convenience of food, and the modified atmosphere fresh-keeping food packaged in trays will be more and more popular with consumers.