Effect of the addition of antimicrobial oregano (Origanum vulgare) and rosemary (Rosmarinus officinalis) essential oils on lactic acid bacteria growth in refrigerated vacuum-packed Tuscan sausage.

Lactic acid bacteria are the main bacterial group associated to meat spoilage. Herbal essential oils are promising alternatives that can be used to retard lactic acid bacterial growth and extend shelf life of meat products. In this study, the influence of oregano and rosemary essential oils on the growth of lactic acid bacteria and the physicochemical properties of refrigerated vacuum-packed Tuscan sausage was evaluated. In addition to the control (without the addition of oil), the sausage samples were separately treated with different concentrations of each essential oil (0.05 wt%, 0.1 wt%, 0.2 wt%, and 0.4 wt%). The shelf life was evaluated as the time to the lactic acid bacteria population to reach the levels of 106 and 107 CFU/g. After the addition of 0.05 wt% and 0.1 wt% of essential oil to the sausage, the rosemary essential oil provided a higher extension of the shelf life of the sausages (approximately 3 and 5 days, respectively) than the oregano essential oil (approximately 1 and 3 days, respectively). After adding 0.2 wt% and 0.4 wt% of essential oil, the oregano essential oil resulted in a larger increase of the shelf life of the samples (about 8 and 14 days, respectively) when compared with the rosemary essential oil (about 7 to 11 days, respectively). All the treatments slowed the growth of the lactic acid bacteria but they did not change the maximum bacterial population. New empirical models that relate the shelf life of the sausage and the maximum specific growth rate of the lactic acid bacteria with the oil concentration were obtained. These results can be applied to model the influence of essential oils on the shelf life of different meat products.