Malolactic Fermentation in Wine by Direct Inoculation with Freeze-Dried<i>Leuconostoc oenos</i>Cultures

Abstract

The identification of 850 bacterial isolates collected from French, Portuguese, Italian, and Spanish wines undergoing malolactic fermentation showed that 77% belonged to the species <i>Leuconostoc oenos</i>. Hybridization of total bacterial DNA using phage DNA as probe indicated that 80% of the <i>L. oenos</i> isolates were lysogenic. <i>L. oenos</i> strains were selected for growth in wine with low pH and high ethanol concentration by use of a turbidostat and further screened for their ability to maintain the adaptation to the wine environment during propagation, freezing, and freeze-drying. Several of the selected freeze-dried strains survived 100% the direct inoculation into commercial wines where they started to grow without a lag phase. The immediate survival and the lag phase of the inoculated bacteria strongly influenced the total duration of the malolactic fermentation. Cultures for direct inoculation may substantially improve the management of malolactic fermentation in winemaking.