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Dry foodstuffs such as cocoa products, potato chips, peanuts, coffee and spices as well as powdered milk and potatoes contain unsaturated fats. These products are therefore sensitive to oxidation and rancidity.
The shelf life is totally dependent on the oxygen (O2) concentrations in the packaging. Even small amounts of oxygen may destroy quality and make the products impossible to sell.
Packages containing particularly sensitive dry foodstuffs such as powdered milk for babies should have oxygen levels of less than 0.2%. The detrimental oxidation processes can be effectively inhibited by replacing oxygen in the package with nitrogen (N2) or carbon dioxide (CO2), or a mixture of these gases.
To maintain an optimum modified atmosphere, the package must have oxygen and moisture barriers. The method used to protect the products against oxygen prior to packaging also plays a key role in the success of Modified Atmosphere Packaging (MAP). It may be necessary to reduce oxygen exposure during pre-packaging processing.
Carbon dioxide slows mould growth
The main spoilage factors for bakery products are mould growth and chemical breakdown. Fermentation may also cause problems in pastries or breads that have been filled. Since the water activity of bakery products is low, the growth of microorganisms other than mould is not often a problem.
Mould is an aerobic microorganism which can be effectively controlled by packaging the produce in a modified atmosphere of carbon dioxide as well as ensuring low levels of residual oxygen (less than 1%). This extends shelf life by a significant amount of days. MAP is especially suitable for rye bread, sweet bakery products, pies and pre-baked bread.
In the case of Danish pastries and other iced bakery products, excessive levels of carbon dioxide can adversely affect the appearance of the icing by dissolving into the fat and causing it to 'melt away'. If the carbon dioxide concentration is balanced by nitrogen, the product's appearance remains unchanged. The loss or adsorption of moisture in bakery products can be prevented by a barrier material.