Environmentally friendly alternatives to plastic packaging have been sought for a long time. Researchers have now succeeded in doing this with food packaging. Instead of plastic, they rely on paper, on which a bioactive coating made of plant-based proteins and waxes is applied. This should not only save plastic, but also extend the shelf life of the food. After use, the packaging is also biodegradable.
Whether cheese, meat, finished goods or fruit and vegetables – most food today is packed in plastic packaging. These protect the food from contamination and damage during transport. However, this also increases plastic waste enormously: In Germany alone, 38.5 kilograms of plastic packaging waste was generated per inhabitant in 2017. The plastic waste ends up in the oceans or is exported abroad and pollutes the ecosystems there. It also breaks down into microplastics and is ingested by animals, for example.
Coating made from natural waxes and proteins
In order to reduce the increasing amount of plastic caused by food packaging, scientists led by Cornelia Stramm from the Fraunhofer Institute for Process Engineering and Packaging have been looking for an environmentally friendly alternative to plastic food packaging. They chose sealable paper bags and wrapping paper as the basis for their packaging. In order to be able to keep food hygienically and for a long time in it, the research team decided to develop a plant-based coating for the paper. To do this, the researchers used proteins and waxes with bio-based additives. For the protein content in the coating, the team experimented, for example, with rapeseed, lupins, whey or sunflowers, which are left over as residues from farms.
Stramm and her colleagues tested beeswax and waxes obtained from the candelilla bush (Euphorbia antisyphilitica) and the Brazilian carnauba palm (Copernicia prunifera) for the wax content of the coating. “We decided on these waxes because they are biodegradable, approved under food law and easily available on the market,” says Michaela Müller from the Fraunhofer Institute for Interfacial Engineering and Bioprocess Engineering. The research team used various techniques to create potential coatings from the proteins and waxes. “The trick is in the mixing ratio and the order in which the individual substances are added,” explained Müller. “The flexibility in the mixing ratio of the substances also enables us to optimize the coating for certain applications.”
Protected from dehydration and spoilage
The scientists then tested how the coated bio-packaging would prove itself in use. “For example, we tested how effectively the respective coating protects the food from external influences such as water vapor, oxygen and mineral oil,” explains Stramm. The coatings were then applied to the paper in a roll-to-roll process, the paper being transported over rollers and the coating being distributed over it as an aqueous dispersion.
It turned out that the components of plastic-free food packaging fulfilled the same functions as conventional packaging. “On the one hand, the proteins serve as an oxygen barrier and the waxes as a water vapor barrier, so fruit, for example, does not dry out so quickly,” reports Müller. “On the other hand, the bio-based additives provide antioxidant and antimicrobial effects. Meat and fish do not spoil as quickly then. Overall, the shelf life of the food is significantly extended. ”The proteins in the coating also prevent mineral oil from being transferred from the paper to the food. Because waste paper in particular can contain residues of mineral oil-containing printing ink, according to the researchers.
Also suitable for deep freezing
According to the scientists, these properties make the novel packaging suitable for all types of food – be it meat, cheese, fruit, vegetables or confectionery. “Our paper-based packaging is also suitable for food that has to be cooled, such as meat,” confirms Müller. “The protective function against oxygen is retained.” And even frozen food should be able to be packaged in it. The paper-wrapped food can be handled and stored in the same way as the plastic-wrapped food, add Stramm and her colleagues. “After use, the packaging goes to the waste paper bin, the coating is biodegradable and does not interfere with paper recycling,” explains Stramm.
The bioactive coating is also versatile: in addition to paper, cardboard could also be coated with it. Printing on the packaging is also not a problem, according to the research team. A manufacturer can therefore print their logo or information about ingredients without contaminating the food. The scientists are currently investigating whether the coating can also be applied directly to food such as fruit or vegetables, thus increasing the shelf life of unpackaged food. From a health point of view, the edible coating should be harmless.
Source: Fraunhofer Society