Ethanol-tolerant lactic acid bacteria strains as a basis for efficient malolactic fermentation in wine: evaluation of experimentally evolved lactic acid bacteria and winery isolates

Abstract

Background and Aims: Reliable malolactic fermentation (MLF) is essential for process efficiency and spoilage prevention in wine. This study extends previous research in our laboratory, aimed at the development and selection of new bacterial strains for reliable MLF in wine, focusing on ethanol‐tolerant lactic acid bacteria (LAB) strains. Sensory differences of seven LAB strains were assessed, including two commercial strains, two ethanol‐tolerant strains derived from directed evolution and three isolates from a high ethanol Grenache. Methods and Results: In this study, the performance of 30 LAB strains was first assessed in fermented chemically defined grape juice media. Seven of the best performing strains were then tested in small‐scale (5 L) fermentations in Shiraz and Shiraz‐Grenache blend wines. All wines were evaluated with a sensory panel using free choice profiling. Conclusions: Despite significantly different MLF kinetics between the strains there were no strain‐specific differences on the final wines. The choice of LAB strain did not adversely change the sensory properties of either wine. Significance of the Study: These findings provide reassurance that the efficient LAB strains (G71 and G55) and the modified directed evolution strains do not compromise the sensory properties of wines despite their marked MLF benefits.