IN DEPTH CHARACTERIZATION OF OENOLOGICAL CHARACTERISTICS OF TWO LACHANCEA THERMOTOLERANS STARTER STRAINS

Abstract

Non-Saccharomyces starter cultures became increasingly popular over the years because of their potential to produce more distinctive and unique wines. The major benefit of the use of Lachancea thermotolerans as a fermentation starter is its ability to produce relevant amounts of lactic acid and reduce alcoholic strength, making it valuable for mitigating negative impacts of climate change on grapes and wine quality. Besides, like any other non-Saccharomyces yeast, L. thermotolerans can significantly affect a whole range of other physico-chemical wine parameters. This study investigated the impact of two L. thermotolerans strains (LT2 and LT5) in fermentation of Malvazija istarska, a Croatian white grape cultivar that in some terroirs and growing seasons requires acidification and/or reduction of alcohol level. A strain of Saccharomyces cerevisiae (EC1118) was sequentially inoculated to finish LT fermentations, and as a monoculture control. Standard physico-chemical parameters were determined by the OIV methods. Organic acids, glycerol, and pathogenesis-related (PR) proteins were determined by HPLC-DAD. Targeted UPLC-MS/MS was performed to analyse phenolic composition, while total phenols were measured by UV/Vis spectrophotometry. Volatile aroma compounds were determined by untargeted metabolomics using GC×GC/TOF-MS complemented by GC-MS targeted analysis. Both L. thermotolerans starters increased total acidity, while the concentration of lactic acid increased from 0.08 g/L in control to 0.73 g/L in LT2 and 0.88 g/L in LT5 treatment wine. Significantly higher concentration of glycerol was determined in wines produced by LT2 strain. Phenol composition was affected without a uniform pattern, while total phenolic content was decreased by LT2 and increased by LT5 strain. Among PR proteins, only a single thaumatin-like protein was significantly reduced by both strains. The use of L. thermotolerans significantly modulated the volatile composition of wines and the most pronounced changes included increased linalool, ethyl lactate, ethyl isobutyrate, ethyl phenyl lactate, and diethyl succinate concentrations. Results from this study contribute to the overall knowledge and understanding of L. thermotolerans contribution to sequential fermentation, with the emphasis on its oenological potential to produce wines with improved acidity and complexity.