MAP modified atmosphere packaging technology in meat packing
Modified atmosphere packaging, also known as MAP, changes the gas composition around the meat to keep it relatively stable for a certain period of time. This ideal gas environment is used to inhibit the growth of microorganisms and extend the shelf life of the meat to achieve the purpose of food preservation.
Meat products that use modified atmosphere packaging in the world markets have developed rapidly, with an annual growth rate of up to 25%. Modified atmosphere packaging replaces the shortcomings of traditional meat vacuum packaging which extend meat’s shelf life by high temperature and high-pressure sterilization that damages the freshness of meat products. In 2018, world’s meat production reached 340 million tons, which is a super large quantity, and meat products are perishable and have a short shelf life in natural environment. Therefore, there is strong motivation to research and update meat preservation technology to it’s best level. Modified atmosphere packaging technology for meat can ensure its natural flavor, reduce juice loss and color changes, and improve meat quality.
This article simply introduces the mechanism, gas composition and main influencing factors of the fresh-keeping of modified atmosphere packaging. On this basis, the research on the fresh-keeping of fresh meat by modified atmosphere packaging technology is introduced in detail. If you’d like to have an overview of various packaging methods for fresh meat, please visit this article page.
How does MAP modified atmosphere packaging extend meat shelf life
The main feature of modified atmosphere packaging is that after packaging with suitable oxygen permeable materials, it replaces the air around the food with the required gas, and actively adjusts the gas environment during meat storage, thereby inhibiting the growth and reproduction of microorganisms, inhibiting the oxidation and rancidity of fat, and slowing down Oxidative discoloration of myoglobin. The gases used in modified atmosphere packaging mainly include oxygen, carbon dioxide, nitrogen, and trace gas components such as carbon monoxide, nitrous oxide, ethylene oxide, and sulfur dioxide.
Modified atmosphere packaging generally uses about 2 to 4 kinds of gases, and their mixture ratios are adjusted to meet the specifications of different meat products and different storage environment.
Rough Gas Mixture Ratio for General Meat Products
|Meat||General mixture ratio|
|Fresh red meat||70% O₂, 20% CO₂， 10% N₂|
|Sausages||33.3% O₂, 33.3% CO₂， 33.3% N₂|
|Ground meat||70% O₂, 30% CO₂|
|Smoked meat||75% O₂, 25% N₂|
|Poultry5||0% O₂, 25% CO₂，25% N₂|
The main role of modified atmosphere packaging gases
The commonly used modified atmosphere packaging gases are CO2 (carbon dioxide), O2 (oxygen), and N2 (nitrogen).
CO2: Inhibits the growth and reproduction of bacteria.
(1) The best antibacterial effect is in the lag phase of the bacteria’s reproduction curve (the inhibitory bacteria index is about 100/100g or less)
(2) It is easily soluble in water and fat at low temperatures
(3) It is effective for most bacteria Aerobic bacteria have antibacterial effects, but are ineffective against anaerobic bacteria and yeasts
(4) Generally, the lowest concentration that inhibits bacteria is 30%
Carbon dioxide has a significant inhibitory effect on aerobic bacteria by changing the permeability of the cell wall and the pH of the environment to inhibit bacterial reproduction and enzyme activity, but it has a poor inhibitory effect on yeast and lactic acid bacteria. Too high a concentration of carbon dioxide will affect the flavor of the food, and may also cause the collapse of the packaging trays.
(1) inhibit the growth and reproduction of anaerobic bacteria
(2) maintain the red color of fresh pig, beef, and mutton
(3) maintain aerobic respiration of the metabolism of fresh fruits and vegetables.
Oxygen in modified atmosphere packaging can promote the production and maintenance of meat myoglobin and inhibit the growth of anaerobic bacteria. At the same time, it can also provide oxygen required for metabolism to ensure the natural color of the meat. However, the presence of oxygen is beneficial to the growth of aerobic microorganisms.
N2: Nitrogen has unique chemical and physical properties that make it suitable for use in food packaging, it is inert which means it will not react with food which can alter their aromas or flavors. Nitrogen is usually used as a filling gas for the mixed atmosphere.
Key Points of the Process of Modified Atmosphere Packaging
Quality control of chilled meat
Studies have shown that the number of microorganisms in the muscle tissue of live animals is very small, and most of the microbial contamination of muscle tissue occurs after the animal is slaughtered. Although chilled meat is under low temperature control (0-4°C), there are still some bacteria on the meat. . Low temperature only inhibits the growth and reproduction of some thermophilic bacteria, but relatively low temperatures are conducive to the growth and reproduction of psychrotrophic bacteria, such as Pseudomonas and Achromobacter. In packages with high CO concentrations, anaerobic lactobacilli can also multiply. Therefore, it is necessary to strengthen the control of the total number of bacteria of the chilled meat before packaging, and at the same time control the quality of inflation and sealing during packaging to reduce various pollution during the packaging process.
Selection of packaging materials
Modified atmosphere packaging should use packaging materials with good barrier properties to prevent the gas in the package from escaping, and at the same time prevent the infiltration of oxygen in the atmosphere to maintain the components of the protective gas in the package. In addition, all packaging materials must have sufficient mechanical strength to enable them to withstand pressure changes during vacuuming.
In addition, the choice of packaging materials should also consider economical and practical, on the basis of not excessively increasing the burden on consumers, to achieve aesthetics and practicality. If the shelf life does not have to be long, packaging materials with general barrier properties, such as PA/PE or polyester (PET)/PE, can meet the requirements. For modified atmosphere packaging that requires a long shelf life, it is best to use high-barrier polyvinylidene chloride (PVDC) or ethylene-vinyl alcohol (EVOH) composite packaging materials.
At present, PVDC high-barrier materials are the most widely used. For example, there is a kind of double-layer laminated film specially used for packaging meat. Its outer layer is a high-density polyethylene film with special structure and performance, and the inner layer is edible paper. The laminated double-layer film is translucent, with a thickness of only 12 Micron, but with good strength, safety, and non-toxicity, it can be directly contacted with meat products. The packaging of meat products with this film can solve the problems that may occur when meat is packaged with ordinary materials and maintain the original color, aroma and taste of meat.
Modified atmosphere packaging of fresh meat
Modified atmosphere packaging for fresh meat includes 2 sections:
- Red meat including pig, beef, and mutton. The red meat packaging is required to maintain the red color of the fresh meat and preserve the freshness.
- Another type is poultry meat such as chickens, ducks, etc., can be called white meat packaging, which only requires antiseptic and fresh-keeping.
Red meat contains bright red oxygenated myoglobin, which can maintain the bright red color under high oxygen environment, and it will be reduced to lavender myoglobin under hypoxic environment. In traditional vacuum-packed red meat, since the oxygen in the package is completely exhausted, the meat appears purple-red, which will be mistaken by consumers for the meat is not fresh, which will reduce the desire to buy.
The protective gas of the modified atmosphere preservation package of red meat is composed of O2 and CO2. The concentration of O2 needs to exceed 60% to maintain the red color of the meat, and the minimum concentration of CO2 is not less than 25% to effectively inhibit the growth of bacteria.
The myoglobin content of various types of red meat is different, and the degree of redness of the meat is also different. For example, beef is darker in color than pork, so the oxygen concentration of different red meats needs to be adjusted in modified atmosphere packaging to obtain the best shelf life. The composition of the modified atmosphere preservation packaging gas of pork is usually 60%-70% O2 and 40%-30% CO2. The shelf life of storage at 0-4 degrees Celsius is usually 7-10 days.
Modified atmosphere packaging of poultry meat only needs to consider extending the shelf life, and does not require the maintenance of color, so the gas of the modified atmosphere packaging of poultry is composed of CO2 and N2, generally 50%-70% CO2, 50%- 30% N2. The shelf life of poultry products in modified atmosphere packaging is about 14 days when stored at 0-4 degrees Celsius.
Modified atmosphere packaging of cooked meat products
In addition to the strict requirements on raw materials for the modified atmosphere packaging of cooked meat, it is very important for the cooking and processing of food to meet the pasteurization standard and the retention time. Cooked meat needs to be quickly cooled in vacuum and cut into thin slices immediately after cooking. If the processing and sanitation conditions at this stage are poor, such as pathogenic bacteria in the air and insufficient disinfection of knives and operators, the food will be contaminated again. Even if the modified atmosphere packaging is used, the shelf life cannot be extended.
The modified atmosphere preservation packaging of cooked food relies on carbon dioxide to inhibit the lag period of the growth and reproduction curve of most aerobic bacteria and fungi, and the most effective inhibition number of carbon dioxide is very low (about 100-200/g). The less the number of pollution, the better the antibacterial effect of the modified atmosphere preservation package, and the longer the shelf life.
Generally cooked meat products are quickly cooled by vacuum, packaged with 25%-35% CO2, 75%-35% N2 modified atmosphere, and the shelf life can reach 40-60 days.