Modified atmosphere
Encyclopedia
Modified atmosphere is the practice of modifying the composition of the internal atmosphere of a package
(commonly food packages, drugs, etc) in order to improve the shelf life
.
The modification process often tries to lower the amount of oxygen
(O2), moving it from 20.9% to 0%, In order to slow down the growth of aerobic organisms and the speed of oxidation reactions. The removed oxygen can be replaced with nitrogen
(N2), commonly acknowledged as an inert gas, or carbon dioxide
(CO2), which can lower the pH
or inhibit the growth of bacteria
. Carbon monoxide
can be used for keeping the red color of meat.
Re-balancing of gases inside the packaging can be achieved using active techniques such as gas flushing and compensated vacuum or passively by designing “breathable” films known as equilibrium modified atmosphere packaging (EMAP). Packets containing scavengers
may be used.
Storage (CAS) was used already In the 1930s when ships transporting fruits had high levels of CO2 in their holding rooms, thus increasing the shelf-life of the product. In the 1970s MA packages reached the stores when bacon and fish were sold in retail packs in Mexico. Since then the development has been stable and the interest into MAP has grown due to consumer demand. This has led to advances for example in the design and manufacturing of Bacon films. New techniques are designed, like the use of anti-fogging layer to improve product visibility. From MAP a new packaging technique − EMAP has been developed.
, seafood
, minimally processed fruit
s and vegetable
s, pasta, cheese, bakery goods, poultry, cooked and cured meats, ready meals and dried foods are packaged. The three major commodity types are fruits and vegetables, meat and meat products, and seafood. It has been estimated that 25-40% of all fresh produce harvested will not reach the consumers table, due to spoilage and mishandling that occurs during distribution.
Meat and fish need very low gas permeability films so for non-respiring products (meat, fish, cheese etc.) high barrier films are used. The initial flushed gas-mixture will be maintained inside the MA package. But fruits and vegetables are respiring products where the interaction of the packaging material with the product is important. If the permeability (for O2 and CO2) of the packaging film is adapted to the products respiration, an equilibrium modified atmosphere will establish In the package and the shelf-life of the product will increase.
gas, which is inert at the temperatures and pressures the packaging is subjected to.
production rates can be reduced, softening can be retarded and various compositional changes associated with ripening can be slowed down.
Oxygen is essential when packaging fresh fruits and vegetables as they continue to respire after harvesting. The absence of O2 can lead to Anaerobic respiration
In the package which accelerates senescence
and spoilage. Too high levels of O2 do not retard respiration significantly and it is around 12% of O2 where the respiration rate starts to decrease. So oxygen is used in low levels (3-5%) for positive effect. When packaging meat and fish, the high CO2-levels are effective bacterial and fungal growth inhibitors. In the case of vegetables and fruits, CO2 is not a major factor since CO2-levels above 10% are needed to suppress fungal growth significantly. Unfortunately higher levels than 10% of CO2 are working phytotoxic for fresh produce. Nitrogen is used as a filler gas since it neither encourages or discourages bacterial growth.
In recent years, there has been debate regarding the use of carbon monoxide (CO) in the packaging of red meat. While no risk was found in the use of low levels of CO, the fact that CO maintains the color of the meat and can, in that way, hide visual evidence of spoilage was raised. The European Food Information Council (EFIC) released a report in 2001 reviewing the data.
(polyvinyl chloride), EVA
(ethylene-vinyl acetate) and OPP
(oriented polypropylene) are not permeable enough for highly respiring products like fresh-cut produces, mushrooms and broccoli. As fruits and vegetables are respiring products, there is a need to transmit gases from and to the package. Films designed with these properties are called permeable films. Other films, called barrier films, are designed to prevent the exchange of gases and are mainly used with non-respiring products like meat and fish.
EMAP films developed to control the humidity level as well as the gas composition in the sealed package are beneficial for the prolonged storage of fresh fruits, vegetables and herbs that are sensitive to moisture. These films are commonly referred to as modified atmosphere/modified humidity packaging
(MA/MH)films.
through package testing
. Incorrect oxygen levels, empty gas cylinders and bad sealing bars can cause imprecise gas blends and poor package seals that can result in product spoilage. Routine package testing with headspace gas analysers, on-line gas analysers and leak detectors assures package quality, hence helps ensuring the shelf life.
Package
Package can refer to:* Packaging and labeling* Package testing* Mail item larger than a letter* Chip package or chip carrier, in electronics, the material added around a component or integrated circuit to allow it to be handled without damage and incorporated into a circuit* Automotive package, in...
(commonly food packages, drugs, etc) in order to improve the shelf life
Shelf life
Shelf life is the length of time that food, drink, medicine, chemicals, and many other perishable items are given before they are considered unsuitable for sale, use, or consumption...
.
The modification process often tries to lower the amount of oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
(O2), moving it from 20.9% to 0%, In order to slow down the growth of aerobic organisms and the speed of oxidation reactions. The removed oxygen can be replaced with nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
(N2), commonly acknowledged as an inert gas, or carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
(CO2), which can lower the pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
or inhibit the growth of bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
. Carbon monoxide
Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
can be used for keeping the red color of meat.
Re-balancing of gases inside the packaging can be achieved using active techniques such as gas flushing and compensated vacuum or passively by designing “breathable” films known as equilibrium modified atmosphere packaging (EMAP). Packets containing scavengers
Scavenger (chemistry)
A scavenger in chemistry is a chemical substance added to a mixture in order to remove or inactivate impurities or unwanted reaction products. Their use is wide-ranged:...
may be used.
Scientific terms
- MAP = Modified atmosphere packaging
- EMAP = Equilibrium modified atmosphere packaging
- MA/MH = Modified atmosphere/modified humidity packaging
History
Controlled AtmosphereControlled atmosphere
A controlled atmosphere is an agricultural storage method. An atmosphere in which oxygen, carbon dioxide and nitrogen concentrations as well as temperature and humidity are regulated.Two major classes of commodity can be stored in controlled atmosphere:...
Storage (CAS) was used already In the 1930s when ships transporting fruits had high levels of CO2 in their holding rooms, thus increasing the shelf-life of the product. In the 1970s MA packages reached the stores when bacon and fish were sold in retail packs in Mexico. Since then the development has been stable and the interest into MAP has grown due to consumer demand. This has led to advances for example in the design and manufacturing of Bacon films. New techniques are designed, like the use of anti-fogging layer to improve product visibility. From MAP a new packaging technique − EMAP has been developed.
Products
Under MA products like red meatMeat
Meat is animal flesh that is used as food. Most often, this means the skeletal muscle and associated fat and other tissues, but it may also describe other edible tissues such as organs and offal...
, seafood
Seafood
Seafood is any form of marine life regarded as food by humans. Seafoods include fish, molluscs , crustaceans , echinoderms . Edible sea plants, such as some seaweeds and microalgae, are also seafood, and are widely eaten around the world, especially in Asia...
, minimally processed fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
s and vegetable
Vegetable
The noun vegetable usually means an edible plant or part of a plant other than a sweet fruit or seed. This typically means the leaf, stem, or root of a plant....
s, pasta, cheese, bakery goods, poultry, cooked and cured meats, ready meals and dried foods are packaged. The three major commodity types are fruits and vegetables, meat and meat products, and seafood. It has been estimated that 25-40% of all fresh produce harvested will not reach the consumers table, due to spoilage and mishandling that occurs during distribution.
Modified Atmosphere Packaging (MAP)
Modified Atmosphere Packaging (MAP) is a technique used for prolonging the shelf-life period of fresh or minimally processed foods. In this preservation technique the air surrounding the food in the package is changed to another composition. This way the initial fresh state of the product may be prolonged. It is the shelf-life of perishable products like meat, fish, fruits and vegetables that will be prolonged with MAP since it slows the natural deterioration of the product. MAP is used with various types of products, where the mixture of gases In the package depends on the type of product, packaging materials and storage temperature.Meat and fish need very low gas permeability films so for non-respiring products (meat, fish, cheese etc.) high barrier films are used. The initial flushed gas-mixture will be maintained inside the MA package. But fruits and vegetables are respiring products where the interaction of the packaging material with the product is important. If the permeability (for O2 and CO2) of the packaging film is adapted to the products respiration, an equilibrium modified atmosphere will establish In the package and the shelf-life of the product will increase.
Equilibrium modified atmosphere packaging (EMAP)
Among fresh-cut produce Equilibrium Modified Atmosphere Packaging (EMAP) is the most commonly used packaging technology. When packaging vegetables and fruits the gas atmosphere of package is not air (O2 21%; CO2 0.038%; N2 78%) but consists usually of a lowered level of O2 and a heightened level of CO2. This kind of package slows down the normal respiration of the product to prolong its shelf-life. Of course there are other factors, like the size of the product, severity of preparation, maturity of the product and type of tissue that have an effect to the shelf-life of an EMA packaged produce.Technology
There are two techniques used in the industry to pack vegetables namely gas-flushing and compensated vacuum. In gas-flushing the package is flushed with a desired gas mixture, as in compensated vacuum the air is removed totally and the desired gas mixture then inserted. The label "packaged in a protective atmosphere" can refer to either of these; an example of a gas mixture used for non-vegetable packaged food (such as crisps) is 99.9% nitrogenNitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
gas, which is inert at the temperatures and pressures the packaging is subjected to.
Gases
The atmosphere in an MA package consists of N2, O2, CO2. It is the altered ratio of these gases that makes a difference in the prolongation of shelf life. By reducing the O2-level and increasing the CO2-level, ripening of fruits and vegetables can be delayed, respiration and ethyleneEthylene
Ethylene is a gaseous organic compound with the formula . It is the simplest alkene . Because it contains a carbon-carbon double bond, ethylene is classified as an unsaturated hydrocarbon. Ethylene is widely used in industry and is also a plant hormone...
production rates can be reduced, softening can be retarded and various compositional changes associated with ripening can be slowed down.
Oxygen is essential when packaging fresh fruits and vegetables as they continue to respire after harvesting. The absence of O2 can lead to Anaerobic respiration
Anaerobic respiration
Anaerobic respiration is a form of respiration using electron acceptors other than oxygen. Although oxygen is not used as the final electron acceptor, the process still uses a respiratory electron transport chain; it is respiration without oxygen...
In the package which accelerates senescence
Senescence
Senescence or biological aging is the change in the biology of an organism as it ages after its maturity. Such changes range from those affecting its cells and their function to those affecting the whole organism...
and spoilage. Too high levels of O2 do not retard respiration significantly and it is around 12% of O2 where the respiration rate starts to decrease. So oxygen is used in low levels (3-5%) for positive effect. When packaging meat and fish, the high CO2-levels are effective bacterial and fungal growth inhibitors. In the case of vegetables and fruits, CO2 is not a major factor since CO2-levels above 10% are needed to suppress fungal growth significantly. Unfortunately higher levels than 10% of CO2 are working phytotoxic for fresh produce. Nitrogen is used as a filler gas since it neither encourages or discourages bacterial growth.
In recent years, there has been debate regarding the use of carbon monoxide (CO) in the packaging of red meat. While no risk was found in the use of low levels of CO, the fact that CO maintains the color of the meat and can, in that way, hide visual evidence of spoilage was raised. The European Food Information Council (EFIC) released a report in 2001 reviewing the data.
Packaging Films
When selecting packaging films (web substrates) for EMAP of fruits and vegetables the main characteristics to consider are gas permeability, water vapour transmission rate, mechanical properties, transparency, type of package and sealing reliability. Traditionally used packaging films like LDPE (low density polyethylene), PVCPolyvinyl chloride
Polyvinyl chloride, commonly abbreviated PVC, is a thermoplastic polymer. It is a vinyl polymer constructed of repeating vinyl groups having one hydrogen replaced by chloride. Polyvinyl chloride is the third most widely produced plastic, after polyethylene and polypropylene. PVC is widely used in...
(polyvinyl chloride), EVA
Ethylene-vinyl acetate
Ethylene vinyl acetate is the copolymer of ethylene and vinyl acetate. The weight percent vinyl acetate usually varies from 10 to 40%, with the remainder being ethylene....
(ethylene-vinyl acetate) and OPP
OPP
OPP or Opp may refer to:* The U.S. E.P.A. Office of Pesticide Programs* Ontario Provincial Police, the provincial police service of Ontario, Canada* Opp, Alabama, a town in southern Alabama, United States* "O.P.P...
(oriented polypropylene) are not permeable enough for highly respiring products like fresh-cut produces, mushrooms and broccoli. As fruits and vegetables are respiring products, there is a need to transmit gases from and to the package. Films designed with these properties are called permeable films. Other films, called barrier films, are designed to prevent the exchange of gases and are mainly used with non-respiring products like meat and fish.
EMAP films developed to control the humidity level as well as the gas composition in the sealed package are beneficial for the prolonged storage of fresh fruits, vegetables and herbs that are sensitive to moisture. These films are commonly referred to as modified atmosphere/modified humidity packaging
Modified atmosphere/modified humidity packaging
Modified atmosphere/modified humidity packaging is a technology used to preserve the quality of fresh produce so that it can be sold to markets far away from where it is grown, extend the marketing period, and to help suppliers reduce food waste within the cold chain...
(MA/MH)films.
Quality assurance of MAP packages
Although Modified Atmosphere Packaging is a well-established process, it is a good practice to maintain tight quality assuranceQuality Assurance
Quality assurance, or QA for short, is the systematic monitoring and evaluation of the various aspects of a project, service or facility to maximize the probability that minimum standards of quality are being attained by the production process...
through package testing
Package testing
Package testing or packaging testing involves the measurement of a characteristic or property involved with packaging. This includes packaging materials, packaging components, primary packages, shipping containers, and unit loads, as well as the associated processes.Testing measures the effects...
. Incorrect oxygen levels, empty gas cylinders and bad sealing bars can cause imprecise gas blends and poor package seals that can result in product spoilage. Routine package testing with headspace gas analysers, on-line gas analysers and leak detectors assures package quality, hence helps ensuring the shelf life.
See also
- Active packagingActive packagingThe terms active packaging, intelligent packaging, and smart packaging refer to packaging systems used with foods, pharmaceuticals, and several other types of products. They help extend shelf life, monitor freshness, display information on quality, improve safety, and improve convenience.The...
- Modified atmosphere/modified humidity packagingModified atmosphere/modified humidity packagingModified atmosphere/modified humidity packaging is a technology used to preserve the quality of fresh produce so that it can be sold to markets far away from where it is grown, extend the marketing period, and to help suppliers reduce food waste within the cold chain...
- Shelf lifeShelf lifeShelf life is the length of time that food, drink, medicine, chemicals, and many other perishable items are given before they are considered unsuitable for sale, use, or consumption...
- PermeationPermeationPermeation, in physics and engineering, is the penetration of a permeate through a solid, and is related to a material's intrinsic permeability...
- Cold chainCold chainA cold chain is a temperature-controlled supply chain. An unbroken cold chain is an uninterrupted series of storage and distribution activities which maintain a given temperature range...