Antimicrobial activity of essential oils against foodborne multidrug-resistant enterococci and aeromonads in planktonic and biofilm state.

The selection and use of natural compounds with antimicrobial activity against foodborne pathogens is of major importance. The present study evaluated the antimicrobial activity of commercial essential oils against multidrug-resistant Enterococcus spp. and Aeromonas spp. Cymbopogon flexuosus and Thymus vulgaris essential oils presented the highest inhibitory zones against both bacterial groups ( p < 0.05). Subsequent determination of the minimum inhibitory concentrations showed values between 0.47 and 1.9 mg/ml for Aeromonas spp. and from 1.9 to 15 mg/ml for Enterococcus spp. The antimicrobial effect of C. flexuosus and T. vulgaris essential oils was also assessed against biofilms. Bacteria in biofilm state were subjected to 30 min or 1 h of exposure to each essential oil and eradication ability estimated by colony counting. Both essential oils exhibited antimicrobial activity against preformed Aeromonas biofilms, but were unable to successfully eradicate biofilms produced by enterococci, in the conditions under investigation. Nonetheless, the presumptive use of essential oils in the food industry should be considered in further investigations.

Assessment of Coagulase-Negative Staphylococci and Lactic Acid Bacteria Isolated from Portuguese Dry Fermented Sausages as Potential Starters Based on Their Biogenic Amine Profile.

The aim of this study was to evaluate the decarboxylase activity of coagulase-negative staphylococci (CNS) and lactic acid bacteria (LAB) involved in meat products fermentation, in order to characterize and select the strains most suitable to be used as safe starter cultures. Isolates were obtained from traditional Portuguese dry fermented meat sausages, identified by PCR and characterized according to their technological properties. Lactobacilli and enterococci were assessed for their bacteriocinogenic potential. Biogenic amines (BA) were screened by culture method and analyzed by RP-HPLC/UV. The screening method, compared with chromatographic analysis, was not reliable for CNS and LAB strains selection. Tyramine decarboxylase activity was present in CNS strains, with a slight production of amines. No other hazardous BA were produced. Among lactobacilli, moderate production of tyramine was related only to Lactobacillus curvatus, with some strains producing putrescine or 2-phenylethylamine. Enterococci were high and moderate producers of tyramine and 2-phenylethylamine, respectively. Staphylococcus xylosus, Staphylococcus equorum, and Staphylococcus carnosus, independent of their genetic and technological profiles and BA production, were adequate for use in meat products, according to the data. Lactobacillus plantarum and Lactobacillus sakei strains could also be selected for starters. PRACTICAL APPLICATION: The selection of coagulase-negative staphylococci and lactic acid bacteria (LAB) isolates were based on their production of biogenic amines in order to avoid this potential hazard production in meat products. The most suitable isolates could be used as safe starter cultures in meat products industry. The staphylococci and LAB selected will achieve particular organoleptic characteristics in meat products and bioprotection from pathogens.

Characterization and Technological Features of Autochthonous Coagulase-Negative Staphylococci as Potential Starters for Portuguese Dry Fermented Sausages.

The manufacture of dry fermented sausages is an important part of the meat industry in Southern European countries. These products are usually produced in small shops from a mixture of pork, fat, salt, and condiments and are stuffed into natural casings. Meat sausages are slowly cured through spontaneous fermentation by autochthonous microbiota present in the raw materials or introduced during manufacturing. The aim of this work was to evaluate the technological and safety features of coagulase-negative staphylococci (CNS) isolated from Portuguese dry fermented meat sausages in order to select autochthonous starters. Isolates (n = 104) obtained from 2 small manufacturers were identified as Staphylococcus xylosus, Staphylococcus equorum, Staphylococcus saprophyticus, and Staphylococcus carnosus. Genomically diverse isolates (n = 82) were selected for further analysis to determine the ability to produce enzymes (for example, nitrate-reductases, proteases, lipases) and antibiotic susceptibility. Autochthonous CNS producing a wide range of enzymes and showing low antibioresistance were selected as potential starters for future use in the production of dry fermented meat sausages.

Eating quality of "Vitela Tradicional do Montado"-PGI veal and Mertolenga-PDO veal and beef.

Physicochemical and sensory characteristics were measured in veal and beef from the Portuguese Mertolenga breed having 3 quality labels as follows: Mertolenga-PDO beef and veal which apply to purebred animals and "Vitela Tradicional do Montado"-PGI veal which applies to crossbred animals. Measurements were made in longissimus lumborum muscle aged for 6days. The temperature 3h post-mortem (T3), cooking losses and Warner-Bratzler shear force (WBSF) reflected carcass weight (CW) differences between groups. The pigment content was influenced by age, with beef having higher values than veal. WBSF correlated negatively with intramuscular fat in Mertolenga-PDO beef, but not on veal. WBSF correlated positively with cooking losses and negatively with myofibrillar fragmentation index, tenderness, juiciness and overall acceptability. Cooking losses and juiciness were the main contributors for the tenderness differences. Vitela Tradicional do Montado-PGI and Mertolenga-PDO veal had lighter colour and were considered tender. The three meat types were well discriminated based on pHu, a* and C* parameters by canonical discriminant analysis.