Uso de emulsões de óleos essenciais no controle de Listeria monocytogenes em salsicha não curada

Abstract

Listeria monocytogenes is a bacterium that causes food infections that has been gaining highlight in the meat products industry, due to its ability to multiply in adverse conditions such as wide pH and temperature ranges and high salt concentrations and to develop on surfaces used in the processing foods and can form biofilms. Due to its physiological characteristics, even if it uses good manufacturing practices, the contamination of products by L. monocytogenes it has been difficult to control. Thus, the use of natural preservatives such as essential oils can offer an alternative for the availability of safe products for the consumer. Thus, the objective of this work was to evaluate the antimicrobial activity of an essential oil emulsion on L. monocytogenes inoculated in uncured sausage and contaminating lactic bacteria, as well as the impact of the oils on the physicochemical characteristics of the product. Therefore, the minimum bactericidal concentrations (MBC) of essential oils of oregano, thyme, coriander, garlic and clove were determined by the broth microdilution method, these being, respectively, 1,0; 1,0; 1,0; 2,0 and 0,5% (v/v). Based on the MBC values and using the Rotational Central Composite Design (RCCD), 27 trials were generated with the mixture of oregano, coriander, clove and garlic oils. All mixtures were bactericidal, being the assay containing 0,16% oregano, 0,05% coriander, 0,14% garlic and 0,03% clove selected for use as a preservative. A treatment with sausages without the addition of nitrite, added with the combination of essential oils and a control with sausages with added 150 mg/kg of nitrite, which were inoculated by immersion in a standardized bacterial suspension of L. monocytogenes (106 CFU/mL) was developed, vacum-packed and stored at 10°C for 15 days. Although the combination of essential oils used has shown to be efficient in controlling L. monocytogenes in vitro, its effect was reduced when added to the sausage formulation. However, no significant difference was observed between the treatments, showing that the essential oil emulsion used had an antimicrobial action similar to that of the sodium nitrite. The emulsion of essential oil did not change the water activity of the sausages, but it contributed to an increase in pH values when compared to the control. The treatment with nitrite was more effective in controlling the lipid oxidation, maintaining lower oxidation values. There was a significant difference in the color of sausages with essential oils, which was expected, due to not adding sodium nitrite, causing them to have a brownish color. Therefore, although the essential oil emulsion used was not able to inhibit the growth of L. monocytogenes and lactic acid bacteria in sausage, it showed an action similar to that of nitrite concerning the growth of these microorganisms, being a possible alternative to replace this preservative. However, it is necessary to carry out more tests with the other combinations of essential oils that were efficient in vitro to find one that could be more efficient in reducing microorganisms in meat products.