Population dynamics of mixed cultures of yeast and lactic acid bacteria in cider conditions

Abstract

The objective of this work was to study the malolactic bioconversion in low acidity cider, according Brazilian conditions. The apple must was inoculated with Saccharomyces cerevisiae or S. cerevisiae with Oenococcus oeni. The control contained the indigenous microorganisms. Fermentation assays were carried out with clarified apple must from the Gala variety. At the beginning of fermentation, there was a fast growth of the non-Saccharomyces yeast population. Competitive inhibition occurred in all the assays, either with inoculated or indigenous populations of the yeast. The lactic acid bacteria count was ca. 1.41·102CFU/mL at the beginning and 106CFU/mL after yeast cells autolysis. The lactic bacteria O. oeni reached the highest population (107CFU/mL) when added to the apple must after the decline of the yeast. The malic acid was totally consumed during the alcoholic fermentation period (80.0 to 95.5 %) and lactic acid was still synthesized during the 35 days of malolactic fermentation. These results could be important in order to achieve a high quality brut, or sec cider obtained from the dessert apple must.