Popular science analysis on modified atmosphere packaging

Popular science analysis on modified atmosphere packaging

Modified atmosphere packaging means that in a certain closed package, through various adjustment methods, the gas in the package is different from the normal atmospheric composition, so as to suppress the physiological and biochemical reactions, physical reactions, oxidative browning, etc. that cause food quality deterioration. So as to achieve the purpose of prolonging food preservation and long-term preservation. Generally, one or more gases such as carbon dioxide, nitrogen, oxygen, etc. are filled into the package according to a certain proportion by a continuous thermal inflatable machine, and the inflatable packaging is completed after hot-pressing sealing.

Modified atmosphere packaging, also known as MAP or CAP abroad, domestically called modified atmosphere packaging or replacement gas packaging, inflatable packaging. Commonly used gases are N2, O2, CO2, combined gas O2+N2 or CO2+N2+O2 (ie MAP). Modified atmosphere packaging technology can be used to preserve the freshness of all kinds of food, prolong the shelf life of food, and enhance the value of food.

Application of CO2 in Food Packaging

High concentration of CO2 can hinder the reproduction of microorganisms such as aerobic bacteria and mold, prolong the stagnation period and exponential growth period of microorganism growth, and play the role of anti-corrosion and anti-mold. my country has successfully used nanotechnology to catalyze CO2 synthesis of degradable plastics. That is, the catalyst used to make plastics from CO2 is "smashed" to the nanometer level to realize the polymerization of catalytic molecules and CO2, so that each gram of catalyst can catalyze about 130 grams of CO2, and synthesize a new packaging material containing 42% CO2. As an environmentally friendly material with excellent degradability, it has broad application prospects.

Application of nitrogen in food packaging

Nitrogen (N2) is an ideal inert gas and has special effects in food packaging: it does not react chemically with food and is not absorbed by food, can reduce the oxygen content in the packaging, and greatly inhibit the growth and reproduction of bacteria, molds and other microorganisms , slow down the oxidative deterioration and spoilage of food, so as to keep food fresh. Nitrogen-filled packaged food can also prevent the food from being squeezed and broken, the food sticking or shrinking into a ball, and maintaining the geometric shape, dryness, brittleness, color, aroma and other advantages of the food. At present, nitrogen-filled packaging is rapidly replacing traditional vacuum packaging, and has been applied to fried potato chips and fries, oil-cooked food, etc. Favored by consumers, especially children and youth, nitrogen-filled packaging is expected to be used in more food packaging.

In the application of N2, the purity and quality of N2 must be paid attention to. The purity of nitrogen gas separated from compressed air by membrane separation or pressure swing adsorption can reach more than 99.9%. The purity of N2 used in food packaging must reach pure nitrogen level (ie safety level).

Application of compound gas in packaged food

The composite modified atmosphere fresh-keeping packaging is collectively referred to as MAP packaging internationally, and the modified atmosphere fresh-keeping gas used is generally composed of CO2, N2, O2 and a small amount of special gases. CO2 can inhibit the growth and reproduction of most aerobic spoilage bacteria and molds; O2 inhibits the growth and reproduction of most anaerobic spoilage bacteria; maintain the color of fresh meat, maintain the oxygen-rich respiration and freshness of fresh fruits and vegetables; N2 is used as filling gas. The composition ratio of the composite gas is properly selected according to the type of food, preservation requirements and packaging materials to achieve the effect of high preservation quality of the packaged food, good preservation of nutrients, truly achieving the original properties and delaying the shelf life of preservation.

Specific applications of modified atmosphere packaging

Modified atmosphere packaging of fresh fish and shrimp

The deterioration of fresh aquatic products and marine fish mainly includes bacteria that decompose trimethylamine oxide in fish meat to release stale trimethylamine, oxidative rancidity of fish fat, enzymatic degradation of fish meat and softening of fish meat, and bacteria on the surface of fish (aerobic Escherichia coli, Anaerobic Clostridium) produces toxic toxins that endanger human health.

The gas used for modified atmosphere packaging of fish is composed of CO2, O2, and N2, of which the concentration of CO2 gas is higher than 50%, which inhibits the growth of aerobic bacteria and mold without causing the fish to seep out; the concentration of O2 is 10%-15% to inhibit anaerobic Oxygen bacteria multiply. The gills and viscera of fish contain a lot of bacteria, which need to be removed, cleaned and treated with disinfectant before packaging. Since CO2 is easy to seep out of plastic film, the packaging material of modified atmosphere packaging for fish needs to use composite plastic film with high gas barrier properties, which can be kept for 15-30 days at 0℃-4℃.

The deterioration of shrimp is mainly caused by microorganisms. Its intrinsic enzymatic action causes the shrimp to turn black. The use of modified atmosphere packaging can keep grass shrimp fresh. First soak the shrimp in 100mg/L lysozyme and 1.25% sodium bisulfite preservative solution, then fill the air-adjustable packaging bag with 40% CO2 and 60% N2 mixed gas, and its shelf life is longer than that of the control sample 22 days extension, which is 6.5 times the shelf life of the control sample.

Modified Atmosphere Packaging of Livestock Fresh Meat

The modified atmosphere packaging of fresh pork, sheep, and beef meat should not only maintain the original red color of the fresh meat, but also preserve the freshness. The gas in the modified atmosphere packaging is composed of O2 and CO2.

In the modified atmosphere preservation packaging of meat, the use of high concentration of O2 can make the fresh meat keep bright red and more vivid, and in an oxygen-deficient environment, the meat quality is lavender. period of up to 30 days. Fresh meat packaging materials also require the use of composite plastic packaging materials with high gas barrier properties.

Modified atmosphere packaging for baked goods and cooked food products

Baked foods include pastries, cakes, biscuits, breads, etc., and the main ingredient is starch. Food spoilage is caused by spoilage caused by bacteria and molds, rancidity caused by fat oxidation, and aging and hardening of starch molecular structure. The gas used in the modified atmosphere packaging of such food is composed of CO2 and N2. Cakes without cream can be kept fresh for 20-30 days at room temperature, and moon cakes and pudding cakes can be kept fresh for 60-90 days with high-barrier composite film at room temperature.

Modified Atmosphere Packaging

Microwave dishes, soybean products and cooked meat products of livestock and poultry can be filled with CO2 and N2, which can effectively inhibit the reproduction of coliform bacteria. Keep fresh for 5-12 days at room temperature of 20°C-25°C, keep fresh for about 30 days at room temperature after conditioning and sterilization at 85°C-90°C, and keep fresh for 60-90 days at 0°C-4°C refrigerated temperature.

Modified atmosphere packaging of fresh fruits and vegetables

After the fruits and vegetables are harvested, they can still maintain the metabolism of absorbing oxygen and expelling CO2, while consuming nutrients. Fruit and vegetable preservation is to reduce the oxygen content in the environment and low temperature storage to reduce the progress of respiration, and to eliminate the CO2 produced by respiration to delay the ripening and aging of fruits and vegetables to achieve the effect of preservation. The modified atmosphere packaging gas of fruits and vegetables is composed of O2, CO2, and N2. The fruits and vegetables are packaged with breathable film, filled with low O2 and high CO2 and replaced with mixed gas, and then sealed, so that the content of O2 in the package is lower than that of air and the accumulated CO2 is higher than that of air. , gas exchange through the film, to achieve a balanced atmosphere that is beneficial to the fresh-keeping environment of fruits and vegetables and maintains weak aerobic respiration.

Modified atmosphere packaging is also suitable for keeping vegetables fresh. Clean vegetables, also known as cut fruits and vegetables, semi-processed fruits and vegetables, are new food processing products that cater to office workers. They are safe, fresh, nutritious and convenient, but they are easy to brown after being cut. The use of modified atmosphere packaging to reduce oxygen levels can greatly extend shelf life. For example, shredded lettuce in the United States prevents browning with 1%-3% O2, 5%-6% CO2 and 90% N2. Modified atmosphere fresh-keeping packaging is also suitable for the preservation of peeled and sliced apples, potatoes, leafy vegetables and other fruits and vegetables. The development of packaging films suitable for the fresh-keeping effect of modified atmosphere packaging of fruits and vegetables is the key to broadening the ways of fresh-keeping of fruits and vegetables.