Dimensioning of food packaging permeabilities - Methods and tools

Wrongly considered as an additional economic and environmental cost rather than an added value in reducing food loss and waste, packaging is nevertheless a key player in improving food preservation, quality and safety, and thus reducing food losses. To fulfill this vital function of food safety and security, the main role expected of packaging materials is to control the transfer of materials between the food, the space within the packaging and the external atmosphere. This role of controlling and regulating the transfer of materials (e.g. gases such as oxygen, vapors such as water vapor) is the foundation of packaging technologies such as modified atmosphere packaging.

Modified atmosphere packaging is based on a change in the gaseous composition of the volume surrounding a food product; air is replaced by a mixture of gases conducive to product quality and extended shelf life. Modified atmosphere packaging can be active, when a well-defined gas mixture is injected directly into the intra-packaging headspace, or created by the use of absorbers (e.g. oxygen) or emitters (e.g. carbon dioxide or ethanol) or other active packaging solutions. It can also be passive (or equilibrium), when the product itself creates the modified atmosphere as a result of its aerobic metabolism (e.g. fresh fruit and vegetables that breathe). In the first case, the role of the packaging is to limit gas transfers with the environment as much as possible, in order to preserve the protective atmosphere around the product. In the second case, on the contrary, regulated transfers will have to be set up. via the packaging and adjust to the product's breathing properties to achieve the optimum equilibrium atmosphere for the product.

With the exception of glass and metal, the other materials used in food packaging (e.g. plastic, paper, cardboard) are not totally impermeable to gases and vapors; they have certain material transfer properties to gases and vapors, or permeabilities. These are also referred to as barrier properties or barrier performance, as in many applications it is a barrier material (i.e. with low permeability) that is required. For example, in the case of oxidation-sensitive products packaged in an inert atmosphere (generally, the earth's initial atmosphere, containing 21% oxygen, is replaced by nitrogen), a very good oxygen barrier property is required to prevent as much oxygen as possible from entering the packaging from the surrounding atmosphere.

While it's vital to know the transfer properties of the packaging materials you're using, it's equally important to know the food's needs in terms of protection against surrounding gases and vapors, so you can choose the right packaging material. For example, a crispy cereal product will need...