The importance of shelf life

In today's commodity society, shelf life is a term that is widely used, especially in the food industry. It is a key indicator because it is the manufacturer's guarantee and commitment to the quality and efficacy of the commodity during the circulation period.

The shelf life mainly depends on four factors, namely the composition of the food, processing conditions, packaging and storage conditions. These influencing factors have been incorporated into the food safety and quality control system HACCP (Hazard Analysis Critical Control Point). Food is a rather cumbersome system in which biological, physical, and chemical changes and reactions are carried out simultaneously. These reactions will reduce the nutritional value of food, produce by-products that affect the nature of food, and even produce toxins. Similar reactions will continue to occur during storage after processing, and the reaction rate at this time depends on the intrinsic properties of the food, the type of packaging, storage and transportation conditions, etc.

01 Reasons for the spoilage of chilled meat

The main reasons affecting the spoilage of chilled meat can be divided into three points

①The reproduction of microorganisms on the surface of the flesh causes the spoilage of the meat.

Its main microorganisms are mainly Pseudomonas under aerobic conditions, and mainly anaerobic and facultative anaerobic lactic acid bacteria and Enterobacteriaceae under vacuum conditions. Most of the bacteria grow on the surface of the meat. The bacteria on the surface of the meat can decompose proteins and other nutrients, so that the surface of the meat is sticky, odorous, and spoiled in a short time.

② Myoglobin in the meat is oxidized and discolored, which affects the appearance and color of the meat.

The color change of meat is controlled by the chemical state of myoglobin and residual hemoglobin. During cold storage, muscle tissue absorbs oxygen in the air, which changes the structure of the body tissue. During the first few days of storage, myoglobin forms unstable oxymyoglobin, which gives fresh meat a bright red color, and then gradually forms stable methemoglobin, which gives fresh meat a dark red (brown) color.

③ The quality of meat is spoiled due to the action of enzymes.

High temperature can significantly increase the activity of various enzymes in fresh meat and microorganisms, and significantly increase the activities of enzymes secreted by microorganisms to its surroundings, which can facilitate various enzymatic reactions and make meat spoiled.

02 Methods of extending shelf life

Vacuum Bag Packaging

For fresh meat, vacuum packaging has the following advantages:

(1) Prevent drying out.

The packaging material provides a barrier to water vapour, preventing drying and keeping the surface of the fresh meat soft.

(2) Prevent oxidation.

When vacuuming, oxygen and air are removed together, and the packaging material is shielded from the atmosphere, so that no oxygen enters the packaging bag, and oxidation is completely prevented.

(3) Prevent the loss of meat flavor.

The packaging material can effectively block the overflow of volatile aromatic substances, and also prevent the transfer of taste between different products.

(4) Avoid freezing loss.

The packaging material insulates the product from the outside world, so ice formation and air drying during freezing minimise losses.

Modified Atmosphere Packaging MAP Trays

The principle of modified atmosphere preservation

The preservation mechanism of modified atmosphere packaging is to protect food with packaging materials with good barrier properties, which means filling the packaging with a certain ideal gas component, improving the environmental components in the packaging under certain temperature conditions, inhibiting the growth of microorganisms and preventing enzymes. Corruption caused by the deterioration, to achieve the purpose of preservation and preservation, thereby extending the shelf life of the product. The gases used are usually carbon dioxide, oxygen and nitrogen or their various combinations, and each gas has a different effect on fresh meat preservation. Generally, the shelf life of fresh meat packaged by air can reach 10 to 14 days.

Modified atmosphere preservation advantages

Modified atmosphere packaging is one of the most common and effective ways to extend the shelf life of all types of food products, including chilled meats. Reasonable modified atmosphere packaging can not only ensure the hygienic quality of meat products, prolong the shelf life, but also have a good impact on the sensory quality of cooled meat. The most commonly used gas components in modified atmosphere packaging are mainly carbon dioxide + oxygen + nitrogen.

The use of this gas mixture is mainly from the point of view of controlling microbial growth and organoleptic quality (such as color). The fresh-keeping effect of this form of Fresh Meat MAP Trays on fresh meat mainly depends on the initial bacterial count of the raw meat, the concentration of carbon dioxide, the presence or absence of oxygen in the packaging bag, the permeability of the packaging material, the storage temperature and the gas composition. It acts as an inhibitor of microorganisms by causing changes in bacterial synthase and enzymatic reaction rates, as well as affecting carboxylation and deamination reactions. The mixed gas is equipped with a certain proportion of oxygen to maintain the color of fresh meat and inhibit the growth of pathogenic bacteria.

The modified atmosphere packaging system is a closed system, in which two processes exist at the same time: one is the physiological serialization process of the product, that is, the metabolic respiration process; The exchange process, these two processes make the air-conditioning system a dynamic system.

The principle of EVOH Barrier MAP Tray modified atmosphere packaging can be summarized into two points: ① Destruction of the environment in which microorganisms grow and reproduce; ② It can maintain a certain activity of the cells inside the food and maintain a certain degree of freshness.

There are two main factors affecting food storage, namely aerobic bacteria and oxidation reactions, both of which require oxygen. Therefore, to prolong the shelf life, it is necessary to reduce the oxygen content of the environment. Modified atmosphere packaging technology can make up for the deficiencies of vacuum packaging to a certain extent and further inhibit the spoilage of microorganisms.

Precautions for Modified Atmosphere Packaging

(1) Processing of fresh meat before packaging.

If the pig is cooled at 0℃-4℃ for 24h after slaughtering, the acid excretion process will occur after the ATP stops moving. The cooled meat treated in this way has far better nutrition and taste than quick-frozen meat and hot fresh meat. In addition, in order to ensure the preservation 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 leakage of gas in the packaging and at the same time prevent the infiltration of oxygen in the atmosphere. Generally, composite packaging films such as PET, PP, PA, and PVDC are used as the base material. To measure the gas barrier properties of plastic films, it is generally expressed by the air permeability coefficient: the smaller the air permeability coefficient, the better the barrier properties. In addition, all packaging materials must have sufficient mechanical strength to withstand pressure changes during vacuum. At the same time, the material is also required to have a certain stiffness so that the packaging bag can be automatically opened and inflated.

(3) Control of product storage temperature.

The influence of temperature on the preservation effect comes from two aspects: one is that the temperature directly affects the activities of various microorganisms on the surface of the body; the other is that the barrier properties of packaging materials are closely related to temperature. The higher the temperature, the better the barrier properties of packaging materials. Low. Therefore, it is necessary to realize the temperature control of the whole process from product, storage, transportation to sales.

03 Summary

At present, vacuum packaging technology can inhibit the growth of microorganisms, prevent secondary pollution, slow down the rate of fat oxidation, make the meat neat and prolong the shelf life of meat products. If the cold meat is vacuum-packed, the preservation will have a certain effect, but its color will be purple-red, and this technology is not perfect.

Only modified atmosphere packaging is an ideal way to extend the shelf life of meat products. Modified atmosphere packaging technology to inhibit the growth of microorganisms, thereby extending the shelf life of meat products. Modified atmosphere packaging can not only make the meat bright red, but also can significantly inhibit the growth and reproduction of spoilage microorganisms, ensure the hygienic quality of meat products, and maintain the good sensory quality of fresh meat products, significantly extending the shelf life.