Influence of the dominance of must fermentation by Torulaspora delbrueckii on the malolactic fermentation and organoleptic quality of red table wine.

Torulaspora delbrueckii can improve wine aroma complexity, but its impact on wine quality is still far from being satisfactory at the winery level, mainly because it is easily replaced by S. cerevisiae yeasts during must fermentation. New T. delbrueckii killer strains were selected to overcome this problem. These strains killed S. cerevisiae yeasts and dominated fermentation better than T. delbrueckii non-killer strains when they were single-inoculated into crushed red grape must. All the T. delbrueckii wines, but none of the S. cerevisiae wines, underwent malolactic fermentation. Putative lactic acid bacteria were always found in the T. delbrueckii wines, but none or very few in the S. cerevisiae wines. Malic acid degradation was the greatest in the wines inoculated with the killer strains, and these strains reached the greatest dominance ratios and had the slowest fermentation kinetics. The T. delbrueckii wines had dried-fruit/pastry aromas, but low intensities of fresh-fruit aromas. The aroma differences between the T. delbrueckii and the S. cerevisiae wines can be explained by the differences that were found in the amounts of some fruity aroma compounds such as isoamyl acetate, ethyl hexanoate, ethyl octanoate, and some lactones. This T. delbrueckii effect significantly raised the organoleptic quality scores of full-bodied Cabernet-Sauvignon red wines inoculated with the killer strains. In particular, these wines were judged as having excellent aroma complexity, mouth-feel, and sweetness.