14C-2 |
Zygosaccharomyces bailii inhibition with mixtures of citral and thymol |
K. Rivera-Carriles1, S. M. Alzamora2, E. Palou1, and A. LÓPEZ-MALO1. (1) Departamento de Ingeniería Química y Alimentos, Universidad de las Américas-Puebla, Sta. Catarina Mártir, Cholula, Puebla, 72820, Mexico, (2) Departamento de Industrias, Facultad de Ciencias Exactas y Naturales - Universidad de Buenos Aires, Santa Maria 300. Tortuguitas, Buenos Aires, 1667, Argentina Debates about the use of antimicrobial agents in food products have been of the public domain for decades, encouraging looking for alternative antimicrobial agents. A wide range of natural antimicrobial sources are being evaluated among them citral and thymol have demonstrated antimicrobial activity. However, data on the effect of natural antimicrobials in combination with is scarce. The effect of selected combinations of citral (Ci, 100, 200, 300, 400, up to 1200 ppm) with thymol (Th, 20, 40, 60 up to 100 ppm) on Zygosaccharomyces bailii growth inoculated in aw 0.99 or 0.95 - pH 3.5 or 4.5 potato-dextrose agar (PDA) were evaluated. PDA prepared with each aw, pH and antimicrobial mixture, was spiral plated with 106 yeast cells/mL suspension, incubated at 25°C, and observed and counted after 10 days. Minimal inhibitory concentration (MIC) was defined as the minimal required individually to inhibit growth (yeast counts < 10 cfu/mL). Fractional inhibitory concentrations (FIC) were calculated from individual and inhibitory combinations; also FIC index of each antimicrobial mixture was computed. MICs were not affected by aw or pH, being 1100 ppm Ci and 100 ppm Th. Several mixtures of Ci and Th inhibit Z. bailii with lower concentrations than those needed when used alone. FICs and FIC index show synergism depending on the antimicrobial concentration in the mixture. Synergistic combinations with FIC index around 0.4 included 200 ppm Ci with 20 ppm Th. FIC index as well as FIC isobolograms (curves deviated to the left of the additive line) show synergistic effects on yeast inhibition when Ci and Th are applied in combination. Furthermore, mixtures of these natural antimicrobials show less pH or aw dependence in its activity than other common antimicrobial agents, which encourages further research on applications of natural antimycotic agents.
Session 14C, Food Microbiology: Food mycology
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