Antimicrobial activity of marjoram and thyme essential oils in poultry meatballs

The aim of the study was to evaluate the possibility of using essential oils from marjoram and thyme to inhibit the growth of microorganisms in poultry meatballs. In the first stage, the values of minimum inhibitory concentrations (MIC) against 10 pathogenic bacteria were determined by serial two-fold dilution method. In the next stage, tests of the level of acceptance of smell and taste by the evaluation committee were carried out and the total number of microorganisms and the number of psychrotrophic microorganisms were determined in chicken fillet meatballs produced with the addition of essential oils of marjoram and thyme in the amount ensuring concentrations of: 0.1 mg/g, 0.5 mg/g and 1 mg/g. The control sample consisted of meatballs without the addition of essential oils. Microbiological tests were carried out on the day of making the meatballs and on the 3rd and 6th day of storage at +4°C. In the study of sensory characteristics, it was found that with the increase in the concentration of essential oil the acceptance of the smell and taste of meatballs significantly decreased. The studies of minimum inhibitory concentrations have shown that essential oils of marjoram and thyme have an inhibitory effect on the growth of microorganisms, and their effectiveness depends on the concentration of the essential oil and the type of bacteria. The highest effectiveness of marjoram essential oil was shown in inhibiting the growth of Klebsiella pneumoniae and Salmonella Enteritidis, for which the MIC value was 0.625 mg/ml. The strongest inhibitory effect of thyme essential oil was found against the following bacteria: Klebsiella pneumoniae and Salmonella Typhimurium, for which the MIC value was 0.039 mg/ml. The research showed that the addition of essential oils significantly reduced the total number of microorganisms in the meatballs. Statistically, a lower total number of microorganisms than in the meatballs without the addition of essential oils was found after 6 days of storage of the balls with the addition of oils at a concentration of 1 mg/g. Essential oils from marjoram and thyme have an inhibitory effect on the growth of microorganisms in poultry meatballs, and their effect depends on the type of oil and the concentration used. However, the use of essential oils in high concentration results in the lack of acceptance of the smell and taste.