SPAIN – Ximena Carrión Granda, from Department of Food Technology of the Public University of Navarra (UPNA) – in Spain, developed some edible coatings that incorporate natural substances with antimicrobial properties that have managed to extend the life of seafood two to four days thanks to the slowdown in the development of spoilage microorganisms.  This research has been part of her doctoral thesis, with which obtained a distinction “cum laude”.

“Films and edible coatings are thin layers and continuous edible material, which are placed on the surface of a food or separating different phases of a food system, with the aim of increasing product quality, increase their shelf life or improve your safety, “explains Carrión Granda, whose doctoral thesis was directed by professor Juan I. Maté Caballero (UPNA) and professor Jordi Rovira Carballido (University of Burgos).

Such coatings create a “barrier being the product and the atmosphere surrounding it.”  “Thus, it protects the food preventing moisture loss, reducing fat oxidation, browning and controlling its quality. In addition, edible coatings may act as carriers of additives, such as antioxidants, minerals or antimicrobials, whose function is reduced growth of microorganisms on the surface of the product, ” said Ximena.

Research on edible coatings has seen considerable growth in recent years to changes in the lifestyle of consumers, who are demanding minimally processed fresh produce without synthetic additives, which last as long as possible and are comfortable in its preparation.  The food industry demand emerging technologies to increase the shelf life of food and provide safe and quality products. So it is with seafood because of its importance in the diet, being an excellent source of protein, vitamins, minerals and fats-polyunsaturated.

“However, it is a very perishable product, even more than red meat or chicken, because of its high surface moisture content and free amino acids. The decomposition process begins with the loss of texture and production of putrid odors, mainly generated by the growth of microorganisms,” according Ximena. Hence antimicrobial edible coatings are considered valid to control microbiological spoilage of seafood emerging technology.

Ximena developed edible films and coatings based on whey protein and chitosan, a polysaccharide derived from chitin, present in the shells of crustaceans (crabs, prawns and lobsters) structural element.  With them she formed “insoluble colorless” coatings, which she said are “different antimicrobial agents, which are gradually released onto the surface of fish and shellfish and reduce the rate of growth of spoilage microorganisms in order to extend their useful life.”

Since the current trend in the food market is directed to the consumption of food free of synthetic preservatives, used natural substances with antimicrobial properties such as essential oils (thyme and rosemary), plant extracts (sage, oregano, garlic and rosemary) and lactic acid bacteria.

These compounds were incorporated in different concentrations, to films whey protein and chitosan and their antimicrobial activity was evaluated against bacteria fourteen related deterioration and pathogenicity of seafood.

“The best formulations were used to evaluate their effectiveness on the microbial growth of fresh tuna steaks and fresh hake and langoustine tails peeled, packaged or without – modified atmosphere – and stored under refrigeration for different time periods presence of air” said the new doctor.

According to their findings, the films containing the essential oils of oregano and thyme and rosemary extract had the highest antimicrobial effectiveness in vitro against pathogenic bacteria (A. hydrophila, L. monocytogenes or S. Typhimurium) and spoilage bacteria (V. alginolyticus or S. putrefaciens).  When applied on different types of fish and seafood, edible coatings were effective to retard microbial growth and increase shelf life of the products processed between two and four days.  Moreover, films containing lactic acid bacteria were successfully tested in vitro against the bacteria L. monocytogenes.

Source: UPNA