Malolactic fermentations (MLF) were induced in a commercially prepared Washington State Chardonnay must to evaluate the influence of timing of inoculation and pre-culture conditions of Oenococcus oeni strains MCW, EQ-54, and WS-8. The must (pH 3.62, 21.5 °Brix) was divided into lots and inoculated with Saccharomyces cerevisiae strain CY3079. Strains of O. oeni were pre-cultured by growing in diluted juice or by re-hydration of freeze-dried strains. Bacteria were inoculated into the musts before (Day 0) or after completion of the alcoholic fermentation (Day 22). Yeast populations and sugar utilization did not differ between the two fermentation experiments. As previously reported S. cerevisiae exhibited a preference for glucose compared to fructose. The yeast CY3079 quickly dominated all fermentations, even with early inoculation of different strains of O. oeni. Soon after inoculation, the viability of all bacterial strains declined. MCW did not recover during the experiment. The population decreases of EQ54 and WS8 were less than MCW, but depended on timing of inoculation as well as the method of preparation of the cultures. MLF ceased most rapidly in fermentation inoculated late with EQ54 rehydrated freeze–dried cultures. None of the fermentations inoculated with EQ54 or WS8 completely finished MLF. Residual malic acid concentration in these wines ranged between 1.38 and 1.81 g/L. All measured values for volatile acidity were well within the range normally found in wines. Wines that underwent MLF possessed higher amount of volatile acidity, the highest concentrations being present in those wines inoculated early with freeze-dried EQ54 and WS8. While MLF was induced in musts or wines inoculated with bacterial stains EQ54 and WS8, strain MCW died off and did not recover during vinification. These results suggest that the optimal time for inoculation of malolactic bacteria depends to a greater extent on the specific strains utilized than on the method of culture preparation.

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