Emulsões de óleos essenciais no controle de Listeria monocytogenes em embutido cozido e curado de peixe

Abstract

Listeria monocytogenes is a bacterium that causes food poisoning that multiplies in different types of foods, especially animal products such as meat, poultry and fish. To ensure consumer safety, meat sausages areadded with nitrate/nitrite salts. However, these preservatives do not have a very effective action against L. monocytogenes. Thus, alternative preservatives that can be used synergistically with nitrate/nitrite salts are of interest. Essential oils are promising for applications in food, especially in meat products, including those made with fish meat. Given the above, this work aimed to evaluate the inhibitory action of essential oil emulsions on L. monocytogenes inoculated in cooked and cured fish sausages, on contaminating lactic acid bacteria, as well as on the physicochemical characteristics of the product. The cooked sausage was made with fillet and mechanically separated meat (CMS) of tilapia and added with curing salts. Minimum bactericidal concentrations (MBC) of essential oils of garlic, oregano, coriander and clove on L. monocytogenes ATCC 19177 were determined in vitro, being respectively: 2%; 1%; 1% and 0.5% (v/v). Based on the CMB obtained, 27 trials containing different mixtures of essential oils were generated using the Central Rotational Composite Design (DCCR). All mixtures showed bactericidal action on L. monocytogenes in vitro. Evaluating the possible sensorial impact of each test on the product, test 10 was chosen, containing the oils of oregano, coriander, garlic and cloves in the respective concentrations of: 0.16; 0.05; 0.14 and 0.03% (v/v). The cooked and cured fish sausages were prepared containing the emulsion of essential oils and 75 ppm of sodium nitrite. A control was developed without the addition of essential oils. After cooking, 25 g samples were inoculated with 10 6 CFU/g of L. monocytogenes, vacuum-packed and stored at 10°C for 12 days. Samples separated for physicochemical analysis were not inoculated. L. monocytogenes and total lactic acid bacteria were quantified and pH, color, water activity, lipid oxidation and residual nitrite were evaluated after 0, 3, 6, 9, and 12 days of storage. There was no significant reduction in either L. monocytogenes or lactic acid bacteria in both treatment and control. However, changes in some physical and chemical characteristics were observed. The color of the product was lighter in the treatment with the addition of essential oils, the pH remained higher on the 9 th and 12 th days of storage. There was no inhibition of lipid oxidation. Although essential oils have great prospects for use as preservatives in the fish sausage industry, the combination of oils used in this experiment was not effective. Thus, it is suggested that the research be conducted using not only emulsions, but nanoemulsions of oil mixtures to optimize the antimicrobial action of essential oils, as well as to study the sensory aspects.