Selection of Oenococcus oeni as starter cultures to induce malolactic fermentation in Nebbiolo wine

Malolactic fermentation (MLF) is the second fermentation of wine that causes a significant evolution of the product and significant changes in its sensory characteristics; this fermentation is principally carried out by Oenococcus oeni. Sometimes its performance has some problems and the use of commercial starter does not help to improve the management of the fermentation. A selection of 0. oeni strains, taken from the collection of the CRA-Centro di Ricerca per l'Enologia, was made to test their speed of adaptation in wine and the time for completing MLF. Different assays were made to test the ability to grow in different media with increasing stressful conditions: low sugar content, malic acid (3g/L) and ethanol (10%); the aim of these steps was to adapt the bacteria to the wine environment. The last step was done in Nebbiolo wine. The two strains obtained at the end of the selection were characterized with molecular biology techniques and they were used as starters in Nebbiolo wine both individually and in pairs. The process of MLF was monitored and the sensory analysis of the obtained wines was made. The results showed that the starters used in the mixture allowed to obtain a wine with a quality comparable with the one obtained using a commercial strain.