Modelling growth/no growth interface of Zygosaccharomyces bailii in simulated acid sauces as a function of natamycin, xanthan gum and sodium chloride concentrations.

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 12 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.