Application of Modified Atmosphere Packaging Technology in Food Industry

Modified atmosphere packaging is also known as MAP or CAP abroad, domestic atmosphere modified atmosphere packaging or replacement gas packaging, and inflatable packaging. Commonly used gases are N2, O2, CO2, mixed gas O2+N2 or CO2+N2+O2 (ie, MAP). Modified atmosphere packaging technology can be widely used for the preservation of various types of food, to extend the shelf life of food and enhance the value of food.

I. Application of CO2 in Food Packaging

A company in Sweden introduced packaging bags, containers and storage rooms filled with 100% CO2 gas to store meat. The high concentration of CO2 can hinder the propagation of aerobic bacteria and molds, increase the stagnation period and exponential growth period of microbial growth, and play a role in antisepsis and mildew. The method enables pork to be stored for 120 days without the need for freezing. If it is repressurized, it can be stored for a longer period of time. This method has attracted great attention from meat exporting countries such as the United States and Australia.

Recently, U.S. experts adopted new technologies to make plastic packaging materials from CO2. That is, using a special catalyst, CO2 and ethylene oxide (or propylene oxide) are mixed in equal amounts to make a new plastic packaging material with the characteristics of glass-like transparency and impermeability; similar to polycarbonate and polyamide. Resin; does not completely decompose into gas at a temperature of 240°C; biodegradability does not pollute the environment and soil.

China has successfully researched and utilized nanotechnology to efficiently catalyze the synthesis of biodegradable plastics from CO2. That is, the use of CO2 to obtain plastic catalyst "pulverize" to the nano level, the catalytic molecules and CO2 polymerization, so that every gram of catalyst catalyzed about 130 grams of CO2, the synthesis of new packaging materials containing 42% CO2. As an environmentally friendly material with excellent degradability, it has broad application prospects.

Second, nitrogen in food packaging applications

Nitrogen (N2) is an ideal inert gas. It has unique effects in food packaging: it does not react with foods and is not absorbed by foods. It can reduce the oxygen content in the package and greatly inhibit the growth and reproduction of microorganisms such as bacteria and molds. , Slow down the oxidative deterioration and rot of food, so as to keep food fresh. Nitrogen-filled packaged foods can also prevent food from being crushing and crushing, sticking or shrinking foods, and maintaining the geometric shape, dryness, crispness, color, and flavor of foods. At present, nitrogen-filled packaging is quickly replacing traditional vacuum packaging, and has been applied to fried potato chips and fries, oil cooking foods and so on. Affected by consumers, especially children and young people, nitrogen-filled packaging is expected to be applied to more food packaging.

The United States applied N2 to increase the strength of thin-aluminum beverage cans. Before beverage canning, nitrogen was dissolved in the beverage; after the beverage can was sealed, nitrogen was released from the beverage, forming a pressure on the can wall, making the beverage can Equivalent to an inflatable can, thereby increasing the intensity of the beverage can, with significant results. The canned beverage will not be damaged during transportation, stacking or on the shelf, nor will it affect the quality of the beverage. This method can also be used for beverage packaging made of polyester plastics.

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

Third, the application of composite gases in packaged foods

The composite modified atmosphere fresh-keeping packaging is collectively referred to as MAP packaging in the world, and the used fresh-keeping gas is generally composed of CO2, N2, O2 and a small amount of special gas. CO2 can inhibit the growth and reproduction of most aerobic spoilage bacteria and molds; O2 inhibits growth and reproduction of most anaerobic spoilage bacteria; maintains the color of fresh meat, maintains oxygen-rich respiration and freshness of fresh fruits and vegetables, and N2 acts as a filling gas. The compound gas composition ratio is properly selected according to the type of food, preservation requirements and packaging materials to achieve high preservation quality of the packaged food, maintaining the nutrient composition, realizing the original characteristics, and delaying the shelf life of preservation.

Composite modified atmosphere fresh-keeping packaging has been widely used at home and abroad.

â–² Fresh fish and shrimps' modified atmosphere packaging Fresh fish and marine fishes are mainly degraded by bacteria to decompose the trimethylamine oxide of fish to release trimethylamine, which has a bad smell, and the fatty acid of fish is oxidized and rancid. The enzyme degrades the fish and softens the fish. Surface bacteria (aerobic Escherichia coli, anaerobic Clostridium) produce toxic toxins and endanger human health.

The gas used for the modified atmosphere packaging of fish is composed of CO2, O2, and N2, in which the concentration of CO2 gas is higher than 50%, which inhibits the growth of aerobic bacteria and molds without causing the fish to seep out; O2 concentration is suppressed by 10% to 15%. Oxygen bacteria multiply. The fish's cockroaches and entrails contain a large amount of bacteria and must be removed, cleaned, and disinfected before disposal. Since CO2 is apt to seep out of plastic films, fish-modified packaging materials need to use a composite plastic film with high gas barrier properties, which can last 15-30 days at a temperature of 0°C-4°C. Tuna uses 35%-45% CO2/55%-65%N2 fresh-keeping packaging for 6 days.

The deterioration of shrimp is mainly caused by microorganisms. Its intrinsic enzyme action causes the shrimp to darken. The use of modified atmosphere packaging can save fresh grass shrimp. The shrimp was first soaked in a preservative solution of 100 mg/L lysozyme and 1.25% sodium bisulfite, and 40% of CO2 and 60% of N2 mixed gas were used to fill the air-filled packaging bags. The shelf life of the shrimp was better than that of the control sample. The 22-day extension is 6.5 times the shelf life of the control sample.

â–² Live Meat Fresh Meat Modified Atmosphere Packaging

The fresh-keeping pigs, sheep, and cattle have fresh-keeping packaging that maintains the original red color of the meat and preserves fresh food. The modified atmosphere is composed of O2 and CO2. The gas composition varies according to the type of meat. The gas composition of pork modified atmosphere packaging is 60%-70%O2 and 30%-40% CO2, and the shelf life at 0°C-4°C is generally 7-10 days (including cooling at 0°C-4°C after slaughter) 24 hours, the ATP active substance is lost, and the texture becomes soft and savory and the palatability is good. Poultry modified atmosphere packaging is mainly preservation and preservation. The fresh-keeping gas is composed of CO2 and N2, and the poultry meat is packaged with 50%-70%CO2/50%-30% O2 in the shelf life of 0-4°C for 14 days.

In meat modified atmosphere fresh-keeping packaging, the use of high-concentration O2 can keep fresh meat brighter and more vivid, in the absence of oxygen the meat is lavender, such as with CO2, N2 and other preservation gas, meat color is lavender, fresh Up to 30 days. Fresh meat packaging materials also require the use of composite plastic packaging materials that have high barrier properties to gases.

â–² Modified atmosphere packaging for baked goods and cooked food products

Baking foods include cakes, cakes, biscuits, breads, etc. The main ingredient is starch. Corruption caused by bacterial molds, etc., rancid deterioration due to oxidation of fats, aging and hardening of the starch molecular structure, etc. cause deterioration of foods. The gas used for the modified atmosphere packaging of such foods consists of CO2 and N2. Cream-free cakes are kept fresh at room temperature for 20-30 days. Moon cakes and pudding cakes can be preserved for 60-90 days at room temperature using high-barrier composite membranes.

The use of microwave dishes, soy products, and cooked meat products for livestock and poultry to fill in CO2 and N2 can effectively suppress the reproduction of coliform bacteria. Fresh-keeping at room temperature 20°C-25°C for 5-12 days, at 85°C-90°C after conditioning sterilization for about 30 days at room temperature, and fresh-keeping for 60-90 days at 0°C-4°C.

â–² fresh fruits and vegetables modified atmosphere packaging fresh fruits and vegetables can still maintain the absorption of oxygen after the harvest of CO2 metabolism, while consuming nutrients. Preservation of fruits and vegetables is achieved by reducing the level of O2 in the environment and reducing the rate of breathing during cold storage, and eliminating the CO2 produced by breathing to delay ripening and aging of fruits and vegetables so as to achieve a preservation effect. The modified atmosphere packaging gas for fruits and vegetables is composed of O2, CO2, and N2. It is packed in air-permeable film and filled with low-O2 and high-CO2 gas and mixed gas. After sealing, the O2 content in the package is lower than air and CO2 is accumulated higher than air. , Gas exchange through the membrane, to achieve the preservation of the environment conducive to fruits and vegetables, to maintain a slight aerobic respiratory balance.

Most fruits and vegetables are packed with 5% O2, 5% CO2, and 90% N2 mixture ratios, and they have a longer shelf life at low temperatures of 6°C to 8°C. Modified atmosphere packaging is used for preservation and preservation of litchi. Treatment of litchi fruit with 10%CO2+90%N2 and 20%CO2+80%N2 for 24hr can not only achieve the purpose of preservation, but also improve the fruit's good fruit rate, keep the peel red, and does not affect the nutrient content. , With high CO2 and low oxygen conditions combined with ozone treatment (4.3mg/M3 concentration) and edible thin coating, can extend the shelf life of strawberries 8-10 days.

American scientists used modified atmosphere packaging test on mangoes, peeled and cut mangoes, used oxygen packaging, mixed gas (N286%, CO210%, O24%) packaging and vacuum packaging, resulting in the longest shelf life of mangoes with mixed gas packaging. During the storage period, the mango has a good appearance such as color and texture, and the damage caused by microorganisms is minimal.

Modified atmosphere packaging is also suitable for fresh food preservation. Net vegetable, also known as cutting fruits and vegetables, and semi-processed fruits and vegetables, is a new food processing product that caters to the working people. It is safe, fresh, nutritious and convenient, but it is easily browned after cutting. Using modified atmosphere packaging to reduce oxygen content maximizes shelf life. For example, cut lettuce in the United States blocks browning with 1%-3% O2, 5%-6% CO2, and 90% N2. Modified atmosphere packaging is also suitable for peeling and slicing fresh fruits and vegetables such as apples, potatoes and leafy vegetables. The development of packaging films that are suitable for fresh-keeping effects of modified atmosphere packaging for fruits and vegetables is the key to broadening the way of keeping fruits and vegetables fresh.