14C-9 |
Ternary mixtures of thymol, carvacrol and potassium sorbate as antimycotic agents |
A. LÓPEZ-MALO1, E. Palou2, A. Argaiz-Jamet3, M. T. Jiménez-Munguia1, and J. Coyotl-Huerta4. (1) Departamento de Ingeniería Química y Alimentos, Universidad de las Américas-Puebla, Sta. Catarina Mártir, Cholula, Puebla, 72820, Mexico, (2) Depto. de Ingeniería Química y Alimentos, Univ. de las Americas-Puebla, Sta. Catarina Mártir, Cholula, Puebla, 72820, Mexico, (3) Laboratorio de Investigación de Alimentos, Universidad de las Américas, Puebla, Apdo. Postal 43, Sta. Catarina Martir., Cholula, Puebla, 72820, Mexico, (4) Departamento de Ingeniería Química y Alimentos, Universidad de las Américas, Puebla, Sta. Catarina Mártir, Cholula, Puebla, 72820, Mexico Phenolic compounds, naturally present in plants, can be used as antimicrobial agents. However, to establish their usefulness, they must be evaluated in combination with other antimicrobial agents to determine whether there are synergistic effects. Individual and combined effects of thymol (Th), carvacrol (Cr), and potassium sorbate (KS) concentrations on the growth of Aspergillus flavus and A. parasiticus in potato-dextrose agar (PDA) adjusted to aw 0.99 and pH 3.5 were evaluated. PDA agar was prepared with sucrose and hydrochloric acid to reach aw 0.99 and pH 3.5; and the necessary amount of Th (0, 25, 50, 75, 100, up to 200 ppm), Cr (0, 25, 50, 75, 100, up to 200 ppm), and/or KS (0, 50, 100, 150 or 200 ppm) was added. For each mold, plates of each combination were centrally inoculated with mold spore suspension, incubated at 25°C, and periodically observed. Inhibition was defined as no observable mold growth after 30 days. For each mold, minimal inhibitory concentrations (MIC) for Th, Cr, and KS were determined, as well as inhibitory concentrations for each ternary antimicrobial mixture. Fractional inhibitory concentrations (FIC) and FIC Index were calculated. MICs were 400 (KS), 300 and 100 (Cr), and 400 and 175 ppm (Th) for A. flavus and A. parasiticus, respectively. Calculated FIC Index were lower than 0.7. FIC index as well as FIC isobolograms (planes deviated to the left of the additive curve) show synergistic effects on mold inhibition when Th, Cr and KS are applied in combination. Ternary mixtures of phenolic compounds (Th and Cr) and potassium sorbate drastically reduced the individual antimycotic concentrations expanding the possibilities to design antimicrobial agents that include naturally occurring ones.
Session 14C, Food Microbiology: Food mycology
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