Use of a D-optimal design with constrains to quantify the effects of the mixture of sodium, potassium, calcium and magnesium chloride salts on the growth parameters of Saccharomyces cerevisiae

The combined effect of NaCl, KCl, CaCl2, and MgCl2 on the water activity (a w) and the growth parameters of Saccharomyces cerevisiae was studied by means of a D-optimal mixture design with constrains (total salt concentrations ≤ 9.0%, w/v). The a w was linearly related to the concentrations of the diverse salts; its decrease, by similar concentrations of salts, followed the order NaCl > CaCl2 > KCl > MgCl2, regardless of the reference concentrations used (total absence of salts or 5% NaCl). The equations that expressed the maximum specific growth (μ max), lag phase duration (λ), and maximum population reached (N max) showed that the values of these parameters depended on linear effects and two-way interactions of the studied chloride salts. The μ max decreased as NaCl and CaCl2 increased (regardless of the presence or not of previous NaCl); however, in the presence of a 5% NaCl, a further addition of KCl and MgCl2 markedly increased μ max. The λ was mainly affected by MgCl2 and the interactions NaCl × CaCl2 and CaCl2 × MgCl2. The further addition of NaCl and CaCl2 to a 5% NaCl medium increased the lag phase while KCl and MgCl2 had negligible or slightly negative effect, respectively. N max was mainly affected by MgCl2 and its interactions with NaCl, KCl, and CaCl2; MgCl2 stimulated N max in the presence of 5% NaCl while KCl, NaCl, and CaCl2 had a progressive decreasing effect. These results can be of interest for the fermentation and preservation of vegetable products, and foods in general, in which this yeast could be present.