A little knowledge about MAP packaging

      MAP packaging (Modified Atmosphere Packaging), also known as gas displacement packaging, is widely used in fresh food (fish, meat, fruits and vegetables), cooked food and grilled food packaging. Compared with frozen packaged food, modified atmosphere packaging products have high fresh-keeping quality and can maintain the original juice, original flavor and color of the food, and meet the requirements of kitchen engineering for ready-to-eat or ready-to-cook.

The principle of preservation of food modified atmosphere packaging:

     Changing the environment of food packaging can extend the preservation period of food, such as vacuum packaging, nitrogen-filled packaging, and modified atmosphere packaging. Modified atmosphere packaging is currently the best packaging form for food preservation. The basic principle of food modified atmosphere packaging is to replace the air in the package with protective gas, so that the food is placed in a protective gas environment, and the growth and reproduction of bacteria and molds that cause food spoilage are inhibited and preserved. The color of fresh meat is protected and fresh. The aging process of fruits and vegetables is delayed, thereby prolonging the shelf life of food.

    Commonly used fresh-keeping gas consists of oxygen (O2), carbon dioxide (CO2), nitrogen (N2) and a small amount of special gases. CO2 gas has the effect of inhibiting the growth and reproduction of most aerobic spoilage bacteria and molds, and is the main gas antibacterial agent in the protective gas. O2 gas has the effect of inhibiting the growth and reproduction of most anaerobic spoilage bacteria, maintaining the color of fresh meat, and maintaining the aerobic respiration of fresh fruits and vegetables to maintain freshness. N2 gas is an inert gas and has no effect on food. As a filling gas, it forms a protective gas with O2 and CO2.

Application of food modified atmosphere packaging:

    Through experimental research, we have obtained the protective gas and preservation period range required for the modified atmosphere preservation packaging of fresh food, cooked food and barbecued food, which are introduced as follows (for reference)

    Fresh aquatic products Fresh fish and aquatic products are perishable foods with high moisture content. When stored at low temperatures, anaerobic bacteria are one of the corruption factors of fresh aquatic products and produce toxins harmful to human health. The fresh-keeping gas is composed of O2, CO2 and N2. The modified atmosphere packaging of fatty fish is the main factor of spoilage due to fatty oxidation acid, and the protective gas is composed of CO2 and N2 gases. Modified atmosphere packaging of fresh aquatic products has a shelf life of 15 to 30 days at a temperature of 0 to 4 ℃ according to the variety and freshness. The packaging film must use a composite plastic film with high gas barrier properties to maintain the gas concentration in the package.

    Fresh meat and poultry Fresh pork, beef, and mutton require preservation and maintain the red color of fresh meat. O2 oxidizes the myoglobin in the meat to oxygenated myoglobin, and the meat is bright red. In anoxic packaging such as vacuum packaging, the oxygenated myoglobin in the meat is reduced to myoglobin, and the meat is lavender, which will be mistaken by consumers as stale meat and affect sales. The protective gas of the modified atmosphere packaging of fresh pork is composed of CO2 and O2. The high concentration of oxygen can maintain the red color of the fresh meat, and the carbon dioxide gas is used for anticorrosion. The fresh-keeping period at a temperature of 0~4℃ is 10~14 days. If CO2, N2 and other gases are used, the fresh-keeping period is 25~30 days. The protective gas of the modified atmosphere packaging of fresh chicken is composed of CO2 and N2, and the fresh-keeping period is 15-20 days at a temperature of 0-4℃. The deterioration of fresh eggs is the loss of CO2 naturally produced on the surface of the eggshell and the reproduction of molds. The protective gas of the modified atmosphere packaging of eggs is composed of gases such as CO2 and O2, and the freshness period is 60 to 90 days at a temperature of 20 to 25 ℃. The packaging film must use a composite plastic film with high gas barrier properties to maintain the gas concentration in the package.

    Fresh fruits and vegetables After the fruits and vegetables are harvested, they still maintain the metabolic respiration activity of absorbing O2 and expelling CO2. If the O2 content in the package is reduced and the CO2 content is increased, the fruits and vegetables can maintain weak aerobic respiration without anaerobic respiration, the aging process of fresh fruits and vegetables is delayed, the metabolism rate is reduced, and the preservation period is prolonged. Modified atmosphere packaging of fresh fruits and vegetables uses gas-permeable plastic film as the gas exchange film. The gas in the package exchanges gas with the atmosphere. O2 is infiltrated from the atmosphere and excess CO2 is discharged from the package to maintain weak aerobic respiration of fruits and vegetables. Modified atmosphere packaging of fresh fruits and vegetables The protective gas is composed of O2, CO2 and N2. The fresh-keeping period of modified atmosphere packaging is determined according to the variety and freshness of fruits and vegetables, such as vegetables, mushrooms, lychees, etc. The fresh-keeping period is 25-60 days at a temperature of 0-6℃.

    Cooked foods The preservation of Western-style enemas and Chinese-style cooked foods such as fish, shrimp, meat, etc. requires antiseptic and fresh flavor. The protective gas of the modified atmosphere packaging of cooked food is composed of CO2 and N2. The fresh-keeping period is 30 to 90 days at a temperature of 0 to 4 ℃, and 5 to 10 days at a temperature of 20 to 25 ℃. The packaging film must use a composite plastic film with high gas barrier properties to maintain the gas concentration in the package.

    Barbecued food The main deterioration of grilled food is mold. The preservation of freshness requires mold prevention and flavor retention. The protective gas is composed of CO2, N2 and other gases. Modified atmosphere packaging of cakes (excluding cream cake) has a shelf life of 20 to 30 days at a temperature of 20 to 25°C. Mooncakes are packaged in a modified atmosphere, and the shelf life is 90-120 days at a temperature of 30-35°C. The packaging film must use a composite plastic film with high gas barrier properties to maintain the gas concentration in the package.

Development of food modified atmosphere packaging products:

     The development and research of various types of food modified atmosphere packaging products include the composition and mixing ratio of the protective gas, the selection of packaging materials, and the test of the freshness period of the modified atmosphere packaging technology. Various foods have different structural composition and fresh-keeping requirements. The composition and mixing ratio of the protective gas must be obtained through experiments to obtain the best fresh-keeping effect and fresh-keeping period. During the storage and sale of food modified atmosphere packaging products, plastic packaging films are used to maintain the gas content in the packaging, which has strict requirements on packaging materials. Most food modified atmosphere packaging products require the use of composite plastic films with high gas barrier properties such as PET/CPP, PET/PE, nylon/CPP, K-PET, while the modified atmosphere packaging of fresh fruits and vegetables requires breathable plastic films such as polyethylene Or a special air-permeable plastic film, and select a suitable plastic packaging film through experiments. The kitchen project requires packaged products to be eaten or cooked to reduce the kitchen labor of urban residents. Therefore, the raw material freshness and pretreatment processing technology of modified atmosphere packaging products have strict requirements, which can make the freshness period of modified atmosphere packaging more ideal.