RESUMO
Probabilistic microbial modelling using logistic regression was used to predict the growth/no growth (G/NG) interfaces of Zygosaccharomyces bailii in simulated acid sauces as a function of natamycin, xanthan gum (XG) and sodium chloride concentrations. The growth was assessed colorimetrically by using 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl-2H-tetrazolium chloride and 2-methoxy-1,4-naphthoquinone as detection reagents. The logistic regression model successfully predicted G/NG probability. The detection reagents used allowed the evaluation of G/NG interfaces in opaque systems with an excellent agreement with the plate count method. Natamycin concentration of 12â¯mg/L was needed to inhibit Z. bailii growth independently of the presence of XG and/or NaCl. Addition of 3.00 and 6.00% of NaCl exerted an antagonistic effect on natamycin action. Furthermore, addition of 0.25 and 0.50% XG decreased natamycin and/or NaCl action. However, an increased in XG concentration to 1.00% decreased yeast growth. Mentioned results highlighted the importance of the correct selection of stress factors applied to inhibit Z. bailii growth.
Assuntos
Antibacterianos/farmacologia , Condimentos/microbiologia , Conservantes de Alimentos/farmacologia , Modelos Biológicos , Natamicina/farmacologia , Polissacarídeos Bacterianos/farmacologia , Cloreto de Sódio/farmacologia , Zygosaccharomyces/efeitos dos fármacos , Antibacterianos/química , Relação Dose-Resposta a Droga , Manipulação de Alimentos , Microbiologia de Alimentos , Conservação de Alimentos , Conservantes de Alimentos/química , Concentração de Íons de Hidrogênio , Modelos Logísticos , Natamicina/química , Polissacarídeos Bacterianos/química , Cloreto de Sódio/química , Fatores de Tempo , Zygosaccharomyces/crescimento & desenvolvimentoRESUMO
Antifungal susceptibilities of Zygosaccharomyces bailii to individual and binary mixtures of citral with selected phenolics were evaluated to identify synergistic combinations. Individual effects of citral, vanillin, thymol, carvacrol, and eugenol concentrations and combined effects of citral with the other phenolic compounds on the growth of Z. bailii were evaluated in potato dextrose agar, adjusted with sucrose to a water activity of 0.99 or 0.95, and hydrochloric acid to pH 4.5 or 3.5. MICs for individual and binary antimicrobial mixtures were identified and then transformed to fractional inhibitory concentrations. Inhibitory concentrations of citral and vanillin were higher than 650 ppm, whereas for thymol, eugenol, and carvacrol, concentrations were lower than 250 ppm for several of the studied water activity-pH conditions. Combining citral with the other phenolic compounds, fractional inhibitory concentration (FIC) and FIC(Index) varied from 0.216 to 0.582. FIC(Index) demonstrated synergistic effects on Z. bailii inhibition when citral was used in combination with vanillin, thymol, carvacrol, or eugenol. Therefore, the relative amount of antimicrobials could be greatly reduced.