Transparent FILMS that extend the life of food and can be eaten. Some may even improve the nutritional composition of fruits and vegetables. The so-called “edible coatings” have been studied in food science and technology laboratories for about twenty years, but today new formulations, raw materials and components are on the way. Come to think of it, the concept is ancient: they have never been called “edible coatings”, but sausage casings, salami skin or cheese crust are nothing more than edible coatings. However, the films on which research is focused today have a very specific purpose, which goes beyond the simple protection of food: on the one hand, they want to help reduce waste and recycle food waste as much as possible; on the other hand, to improve the life of food in the path of commercial distribution and home preservation.
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Reuse of materials
The first purpose is achieved by using raw materials deriving mostly from food leftovers and waste or from secondary products of the agro-food industry, such as chitosan and collagen. «Every year around 8 million tons of crustaceans are produced in the world. 40-70% of the weight of crustaceans processed for human consumption consists of exoskeleton, that is the external structure of shrimps, prawns, crabs. This waste material contains 15-40% of a substance called chitin, from which chitosan is made. Collagen, on the other hand, is extracted from the connective tissue of tendons, ligaments, bones and skin, especially in cattle and pigs “, explains Annamaria Ranieri, Professor of the Department of Agricultural, Food and Agro-Environmental Sciences of the University of Pisa, who is testing the use of these two waste from the food industry for the production of films capable of preserving, protecting and, as emerged from the latest experiments , also enrich the coated food with bioactive substances.
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Maintenance of organoleptic qualities
«The coating acts like a membrane that reduces the passage of oxygen inwards, slowing down the oxidative processes that lead to the deterioration of the food. As a consequence, life is prolonged and the organoleptic qualities of the food are maintained ”, says the expert. During an experiment in which peaches, apricots and carrots were stored at about 8 degrees for three weeks, the samples covered with the coating with the highest concentration of chitosan are visually deteriorated much less. «Chitosan is an antibacterial, therefore the food, coated in this way, keeps better being more protected from aggression by viruses or bacteria. We have also tried to include substances in the formulations, such as antioxidants or vitamins, to enrich the foods from a nutritional point of view and to protect them even more ». The Pisan researchers in particular used tyrosol, an antioxidant contained in large quantities in olives, and tested it on tomatoes. “We dissolved the tyrosol in the formulation of the edible coating and we found that, once the film formed in contact with the fruit, the substance also migrated inside the vegetable, that is to say in the pulp, which generally represents the less rich part of antioxidant substances with respect to the peel ». An interesting nutritional advantage considering that many people have the habit of removing the peel before eating fruit.
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Substances extracted from food industry waste
Similar research is also conducted by the research group of Marco Dalla Rosa, Professor of Food Technology at the University of Bologna, who with a study on blueberries has shown how edible coatings made with polysaccharides, proteins, lipids, substances extracted from food industry waste (such as chitosan) and added with antimicrobial components o antioxidant (spices or citrus essential oils) are able to improve the nutritional and qualitative characteristics of berries. “Edible coatings can increase the life of a food product by 20-30% because they slow down its metabolic and microbial activity”, Dalla Rosa specifies: “A fruit, for example, has a longer life by losing less weight and less water “. The University of Bologna is also testing edible coatings on bread and confectionery baked goods to lengthen their shelf life and freshness, which generally shrink after one day of purchase, and even on cheeses and fish.
The optimal environmental saving objective is that edible coatings can also minimize the use of traditional packaging. They cannot replace packaging, but they can increase its effectiveness and reduce the quantity used with a view to sustainability.
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