Packaging plays a very important role in preserving, protecting and preventing the food from getting spoiled. Faulty packaging can undo all the attempts of preserving the food made by the food processor during the manufacturing process. That is why, a food manufacturer must have appropriate knowledge about the different types and functions of packaging.There are a number of packaging techniques and materials available to suit the variant degree of food products in terms of their size, nature, bulk density, perishability e.t.c. Although packaging serves multiple purpose at the same time, but the most important purpose it should serve is – ‘Extending the shelf life of food’. One such technique of packaging that extends the shelf life of food by packaging the product (in a gas impermeable package) under a preservative gaseous environment is called Modified Atmosphere Packaging (MAP).
What is Modified atmosphere packaging?
Modified Atmosphere Packaging(MAP) can be defined as the enclosure of food in a package in which the atmosphere inside the package is modified or altered to provide an optimum atmosphere for increasing shelf life and maintaining food quality. Modification of the atmosphere may be achieved either actively or passively.
MAP is used to delay deterioration of foods that are not sterile and whose enzymic systems may still be operative. With the exception of baked goods, MAP is always used in association with chill temperatures, usually taken as −1°C to +7°C. Holding food at chill temperatures is widely used as an effective short-term preservation method, which has the effect of retarding the following occurrences:
- Growth of microorganisms
- Postharvest metabolic activities of intact plant tissues, and postslaughter metabolic activities of animal tissues
- Deteriorative chemical reactions, including enzyme-catalyzed oxidative browning, oxidation of lipids, chemical changes associated with color degradation, autolysis of fish and loss of nutritive value of foods in general
- Moisture loss
Related Read: Controlled Atmosphere Packaging
The preservative effect of chilling can be greatly enhanced when it is combined with modification of the gas atmosphere. This is because many deteriorative reactions involve aerobic respiration in which the food or microorganism consumes O2 and produces CO2 and water. By reducing O2 concentration, aerobic respiration can be slowed. By increasing CO2 concentration, microbial growth can be slowed or inhibited
GASES USED IN MAP
The normal composition of air by volume is 78.08% N2, 20.95% O2, 0.93% argon (Ar), 0.03% CO2 and traces of nine other gases in very low concentrations. The three main gases used in MAP are O2, CO2 and N2, either singly or in combination. Noble or “inert” gases such as Ar are being used commercially for a wide range of products.
- CARBON DIOXIDE
- CARBON MONOXIDE
- NOBLE GASES
- GAS MIXTURES
METHODS OF CREATING MA CONDITIONS:
In this approach (also known as commodity-generated MA), an atmosphere high in CO2 and low in O2 passively evolves within a sealed package over time as a result of the respiration of the product. Ideally, the gas permeabilities of the packaging film are such that sufficient O2 can enter the package to avoid anoxic conditions and the occurrence of anaerobic respiration, while at the same time excess CO2 can diffuse from the package to avoid injuriously high levels. Passive modification is commonly used for MAP of fresh respiring fruits and vegetables.
Several methods can be used to actively modify the gas atmosphere inside a packaged product:
- vacuum packaging : where the air is removed under vacuum and the package sealed. This method finds widest application for the packaging of flesh foods, particularly red meat.
- A two stage method involves first removing the air inside the package using a vacuum followed by flushing with the desired gas mixture. This creates the desired MA immediately after packaging compared to the passive approach.
- no vacuum is used but a gas mixture is injected into the package and the air swept or flushed out immediately prior to sealing, resulting in residual O2 levels of 2–5%. For O2-sensitive products, the two-stage method is preferred.
Regardless of whether vacuum or gas flush packaging is used to create an MA, the package itself must provide a barrier to permeation over the expected shelf life, otherwise the beneficial effects of reducing O2 will be lost.
Advantages and Disadvantages of Modified Atmosphere Packaging(MAP):
- Shelf life increase from 50% to 400%
- Reduced economic losses due to longer shelf life
- Decreased distribution costs, longer distribution distances and fewer deliveries required
- Provides a high quality product
- Centralized packaging and portion control
- Improved presentation—clear view of product and all-around visibility
- Little or no need for chemical preservatives
- Sealed packages are barriers against product recontamination and drip from package
- Odorless and convenient packages
- Added costs for gases, packaging materials and machinery
- Temperature control necessary
- Different gas formulations for each product type
- Special equipment and training required
- Potential growth of food-borne pathogens due to temperature abuse by retailers and consumers
- Increased pack volume adversely affects transport costs and retail display space
- Loss of benefits once the pack is opened or leaks
- CO2 dissolving into the food could lead to pack collapse and increased drip
- slowing down in the cooling rate of the packaged products
- increased potential for water condensation within the package, which may encourage fungal growth.
EQUIPMENT FOR MAP
Equipment for MAP must generally be capable of removing air from the package and replacing it with a mixture of gases.
- Form-fill-seal machines:
FFS machines can either form pouches (vertically or horizontally), or thermoformed trays with a heat sealed lid, from rollstock.
- Chamber machines:
Here, the filled package (either a preformed pouch or tray inside a bag) is loaded into a chamber, a vacuum is pulled and the package is then flushed with the gas mixture and heat sealed.
- Snorkel machines:
Snorkel machines operate without a chamber. The product is placed inside a large flexible pouch (or bag) and positioned in the machine. Snorkels or probes are inserted into the pouch and remove air, after which the vacuum is broken by the addition of the desired gas mix. The probes are then removed and the package is heat sealed.
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