Comparison of Brettanomyces yeast presence in young red wines in two consecutive vintages

Two hundred young wines from the D.O.Ca. Rioja (Spain) coming from two consecutive vintages, 100 wines from 2012 and 100 wines from 2013, were analysed and compared with respect to physicochemical composition and Brettanomyces presence. This microorganism was tested using two techniques: qPCR and an odorimetric test. In 2013, the harvest was characterized by late ripening, health problems with the grapes, and difficulties during vinification. Differences between 2012 and 2013 wines were found both for analytical parameters and as for the presence of the spoilage yeast, Brettanomyces, which was much more prevalent in the 2013 vintage. Moreover, the results showed that for some wines in which Brettanomyces was detected by qPCR at concentration higher than 10(2) cells/ml, no Brett character was found in the odorimetric test. This would indicate that the contamination of a wine by this yeast is not the only factor involved in spoilage. The strains of Brettanomyces, their physiological state, and viability, besides the specific composition of wine, could be important in the Brett character appearance. In this study, the wines which developed spoilage in the odorimetric test had slightly lower pH and alcoholic strength values, but higher levels of volatile acidity, reducing sugars and density in comparison with those wines than were not affected. Most of these factors are favourable for the development of Brettanomyces.