Atividade bactericida de antimicrobianos naturais sobre Listeria monocytogenes inoculada em mortadela

Abstract

This thesis was a central proposal to evaluate the antimicrobial activity of chitosan and essential oil of Syzygium aromaticum added at different concentrations in mortadella on Listeria monocytogenes, as well as the incorporation of fiber to the meat product, its activity on lipid oxidation and sensory acceptance of the product. To achieve such proposal three articles were developed. At first, it was evaluated the minimum bactericidal concentration of chitosan on Listeria monocytogenes in vitro and the inhibition of this microorganism in situ and physico-chemical characterization of mortadella with different concentrations of chitosan during refrigerated storage. There was no significant difference (p <0.05) in the pH throughout the 30 days of storage both for control and for mortadella containing higher concentrations of chitosan. The residual nitrite showed a significant difference (p <0.05) for all analyzed samples. The lipid oxidation of all treatments were significantly affected (P <0.05) during storage. The values of the four samples for enumeration of Listeria monocytogenes in both whole and sliced mortadella were significantly different (p <0.05) where, in the samples containing higher concentrations (2 and 3%) of chitosan, it was found a reduction of 3 logarithmic cycles. In the second article, the objective was to evaluate the effects of adding different concentrations of chitosan (0, 1, 2 and 3%) in technological and sensory characteristics of mortadella. The instrumental color indices did not differ (P> 0.05) among treatments, the parameters of hardness and chewiness reduced (p <0.05) with the increasing addition of chitosan in the formulation. The samples’ hedonic notes were between 6 and 8 (‘slightly liked’ and ‘enjoyed’). At CATA, the most accepted samples were those that contained 2 to 3% of chitosan, suggesting that control presented "light pink color", "meat flavor", "salty", "aftertaste of fat", "stale taste" and the sample with 3% chitosan presented “characteristic flavor of mortadella ". In the third article, the aim was to evaluate the synergistic effect of chitosan and essential oil of Syzygium aromaticum, with reduction of sodium nitrite on Listeria monocytogenes ATCC 19117 inoculated in mortadella and its activity on lipid oxidation of the product, which was used the Central Composite Design (CCD). The concentration of chitosan influenced the pH values in the studied mortadella, both on the first day of storage and after thirty days. For residual nitrite there was clearly a smaller reduction of the residual nitrite concentration when in higher concentrations of chitosan. It can be seen that the highest concentrations of Syzygium aromaticum essential oil presented antioxidant in TBARS analysis. The highest concentrations of essential oil of Syzygium aromaticum and chitosan influenced the counting of Listeria monocytogenes among the treatments in both the first day of storage and after thirty days. Therefore, with the results of this thesis it can be concluded that there is technological feasibility, antioxidant activity and antimicrobial activity against a pathogen of great interest in the meat industry, in the addition of chitosan and essential oil in meat products, obtaining also a product source of fibers.