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 log2 transformations of maximum specific growth rates (mu) and lag times (lambda) as responses, it was deduced that mu depended on the temperature (linear and quadratic effects); while lambda 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 mu were: Ztemp, mu (harmonic average of ztemp, mu)=6.90, zNaCl, mu=-5.61. The values for lambda were: ztemp, lambda=-4.87, zNaCl, lambda=3.36, and zpH, lambda=-1.08. The product of the specific growth rate and the lag, h0 (the "work to be done" during the lag phase) depended (p<0.05) on pH. The effects of NaCl and temperature on h0 were not significant though they produced a 1.32- and 1.23-fold increase on it.