Consumers are becoming more and more demanding with the foods they eat and also prefer preservation technologies which do not modify the nutritional and sensorial properties of the end-product. In response to this, researchers of Valencia’s Polytechnic University (UPV) and of the Agrochemistry and Food Technology Institute (IATA), a center of the Spanish National Research Council (CSIC), have studied the effectiveness of new antimicrobial systems based on the use of essential oils extracted from plants such as thyme or cinnamon to improve the preservation of foods.

On the one hand, consumers want foods to have a long shelf life that facilitates its home storage for a lengthy period. But they also prefer that preservation technologies applied to this end do not modify the nutritional and sensorial properties of the foods, which is common with thermal processes, and also that they do not add additives. Taking on these limitations, therefore, requires the development of new microbial stabilization techniques, which include new antimicrobial agents, according to the researchers. 

The novelty of this work consists on the chemical immobilization of the essential oil on platforms that are authorized for being used with foods, in a way that they keep the traditional antimicrobial activity of essential oils without reaching the food.

To date, they have been applied to treat the microorganisms that alter wine and managed to stunt their growth. based on the results of this work, new research is being carried out which suggests that the antimicrobial systems developed can be used to stabilize wines micro-biologically, thus decreasing the number of additives including sulfites.

The design of new antimicrobial systems comes from a prior collaboration between the groups of researchers from the UPV’s Food Technology Department and members of the Molecular Recognition and Technological Development Institute (IDM-UPV), a development which is protected with a patent.

No smell or taste

“Currently, the use of essential oils entails a strong smell and taste, low stability and interaction with the food matrix that decreases its antimicrobial effect. Our system prevents these drawbacks so that the consumer perceives the product as if it had not been processed – while the removal of altering microorganisms is complete,” explains María Ruiz, a researcher at the UPV’s Food Technology Department.

The systems used in this study by the UPV and IATA researchers are based on the immobilization of components of the essential oils on silica and cellulose microparticles as well as cellulose membranes. This way, the antimicrobials can’t reach the food and its smell can therefore not be perceived by the consumer. 

“Furthermore, if the immobilization conditions are properly controlled, you can get the essential oil components to preserve or even increase their antimicrobial properties,” adds Ruiz.

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The antimicrobial systems developed by UPV and IATA researchers could be used as new food additives to stabilize other products micro-biologically, to replac or reduce the addition of synthetic chemical preservatives. They could also be used for the design of a new cold pasteurization process for liquid foods.