Antimicrobial activity of essential oils against Vancomycin-Resistant enterococci (VRE) and Escherichia coli O157: H7 in feta soft cheese and minced beef meat

Eleven essential oils (EOs) were evaluated for their antibacterial properties, against Vancomycin-Resistant Enterococci (VRE) and E. coli O157:H7. EOs were introduced into Brain Heart Infusion agar (BHI) (15ml) at a concentration of 0.25 to 2 percent (vol/vol) to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) for each pathogen evaluated. Results showed that the most active essential oils against bacteria tested were thyme oil, with MIC90 and MBC90 for the VRA strains of 0.25 percent and 0.5 percent, respectively. Eucalyptus, juniper and clove oils were the least potent agent, with MIC90 and MBC90 of 2 percent. Furthermore, the inhibitory effect of these EO were evaluated against VRE and E. coli O157:H7, experimentally inoculated (10³ cfu/g) in Feta soft cheese and minced beef meat, which was mixed with different concentrations (0.1 percent, 0.5 percent and 1 percent) of the EO and stored at 7 ºC for 14 days. Out of eucalyptus, juniper, mint, rosemary, sage, clove and thyme oils tested against target bacteria sage and thyme showed the best results. Clove and mint did not show any effect on VRE and E. coli O157:H7 in both kinds of studied foods. The addition of thyme oil at concentrations of 0.5 and 1 percent caused best significant reduction in the growth rate of VRE and E. coli O157:H7 in cheese and meat at 7 ºC. It is concluded that selected plant EOs can act as potent inhibitors of both microorganisms in a food product. The results revealed the potential of thyme oil as a natural preservative in feta soft cheese and minced beef meat against VRE and E. coli O157:H7 contamination.

Avaliação físico-química e organoléptica do estado de conservação de carne bovina moída, preparada industrialmente / Physico-chemical and organoleptical evaluation of storage condition of industrially processed minced beef

Através de exames físico-químicos e organolépticos, avaliou-se o estado de conservação de carne bovina moída, preparada industrialmente e embalada a vácuo, quando mantida a temperatura de 8°C, após a abertura da embalagem. As análises foram realizadas nos 1°, 3°, 5° e 7° dias de armazenagem. Os resultados do pH mostraram que houve queda significativa (p<0,05) do 1° ao 7° dia, passando de 5,67 a 5,51. No mesmo período, os teores de bases voláteis totais aumentaram significativamente (p<0,05) de 14,99 para 19,64 mgN/100g. A proporção de amostras positivas para a pesquisa de amônia foi de 16,6% no 3° dia, 70% no 5° e 100% no 7°, havendo um aumento gradativo em relação ao 1° dia, quando 100% das amostras apresentaram resultado negativo. Os resultados mostraram que a carne bovina moída preparada industrialmente e embalada a vácuo pode ser considerada de boa qualidade até o 3° dia de armazenagem a 8°C, justificando sua comercialização como carne resfriada.

Storage condition of minced beef industrially processed and vacuum packed was evaluated through physico-chemicaland organoleptical analysis. The tests were performed on the 1st, 3'd, Sth and 7th days of storage at 8°C, after package opening. A significant decrease (p<0.05) was found in pH value from 5.67 in the 1st day to 5.51 in the 7th day. The total volatile bases increased significantly (p<0.05) from 14.99 to 19.64 mgN/1 OOg in the same period. The percentages of ammonium in positive samples were 16.6% in the 3rd day, 70% in the 7th day and 100% in the 7th day. In the 1st day no sample gave positive results. From this results, it can be concluded that minced beef may be considered of good quality up to the 3rd day of storage at 8°C, if industrially processed and vacuum packed and, in this way, be commercialized as fresh refrigerated meat.