What modified atmosphere for dry products?

As soon as they come into contact with air, foods undergo deterioration which affects their color, appearance, texture, taste and shelf life. Packaging in a protective atmosphere helps slow down these phenomena. How does this happen in the particular case of dry products?

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Protective atmosphere packaging consists of replacing the air inside the packaging with a gas (or a mixture) with protective properties. It uses the natural components of the air.

Combining gas with packaging helps prevent physical, enzymatic and microbiological deterioration to preserve the freshness and quality of foodstuffs. Packaging in a protective atmosphere helps preserve the appearance, color and nutritional and organoleptic properties of the product during its shelf life, and protects it from bacterial contamination.

Characteristics of dry products

The family of so-called “dry” foods is characterized by products with a water content of less than 12%. These are, for example, seeds and dried fruits (walnuts, hazelnuts, almonds, etc.), powdered milk, coffee, tea, chips, protein powders, etc.

Poor in water, they are often rich in oils and fats. The main conservation problems encountered are the oxidation of fats, pigments and aromas, making the food taste less good.

What atmosphere to use?

Only the elimination of oxygen from the air and its replacement with nitrogen is necessary to prevent the oxidation of fats. There are no microbial developments to fear given the degree of dryness of the products. To ensure a long shelf life, it will be necessary to reach a threshold of a maximum value of 2% in residual oxygen in the packaging containing the food.

Special case of dry products intended for export

The use of CO2 (pure or in a mixture) makes it possible, thanks to its high solubility in fats, to limit the effects of pressure during thermal or barometric variations during transport.

Since food is also sensitive to light and UV, packaging is sometimes made of aluminum or with anti-UV protection.

These products, which are not rich in water, are generally stored at room temperature. Packaged in a protective atmosphere, in bags or trays, their shelf life is up to 5 times longer than in air. They can be stored like this for several months. The expiration date appears on the packaging label with the words “best consumed before…”.

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Dry Products

Product	Mixture			TEMPERATURE	Time*
	N₂	CO₂	O₂
Ground/bean coffee	100%	or	100%	Ambient	> 6 months
Powdered milk	100%	or	100%	Ambient	2-3 months
Dried fruits: dates figs prunes apricots	80%	20%		Ambient	4-5 months
Salted fruits: peanuts pistachios cashew nuts	100%	or	100%	Ambient	> 6 months
Potato Chips Flakes	100%	or	100%	Ambient	4 months

* The DLCs are given for information purposes only.

If the choice of packaging atmosphere is important, the other elements of the system, the film and the packaging machine, are just as key to the success of modified atmosphere packaging. To hope for a long shelf life, particular attention must also be paid to the preparation of products which must be of impeccable hygiene.

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