Use of the generalized z-value concept to study the effects of temperature, NaCl concentration and pH on Pichia anomala, a yeast related to table olive fermentation

The effects of temperature, NaCl concentration and pH on the growth and lag phase time of Pichia anomala was studied by means of a central composite design. From the response surface obtained, using log 2 transformations of maximum specific growth rates ( μ) and lag times ( λ) as responses, it was deduced that μ depended on the temperature (linear and quadratic effects); while λ was affected (linear effects) by the three variables. The relative effects of variables were studied by means of the generalized z-value. The results for μ were: Z temp, μ (harmonic average of z temp, μ ) = 6.90, z NaCl, μ = − 5.61. The values for λ were: z temp, λ = − 4.87, z NaCl, λ = 3.36, and z pH, λ = − 1.08. The product of the specific growth rate and the lag, h 0 (the “work to be done” during the lag phase) depended ( p < 0.05) on pH. The effects of NaCl and temperature on h 0 were not significant though they produced a 1.32- and 1.23-fold increase on it.