Investigating the influence of a wine yeast consortium on population dynamics, alcoholic and malolactic fermentation

[摘要] ENGLISH ABSTRACT: Non-Saccharomyces (NS) starter cultures of species such as Metschnikowia pulcherrima,Torulaspora delbrueckii, Pichia kluyveri and Lachancea thermotolerans, have receivedattention for their desirable properties and contributions in winemaking. These include theproduction of volatile compounds or enzymes to modify organoleptic attributes. Most studieshave focussed on the use of single NS at a time with Saccharomyces cerevisiae to study theabove contributions and properties; including effects on malolactic fermentation (MLF).However, there is growing interest in using complex multi-starter cultures to enhance winearoma. Indeed, commercial products such as Anchor Alchemy II (Anchor Yeast), whichcomprises of different strains of S. cerevisiae, and Melody™ (CHR Hansen), comprising ofS. cerevisiae, L. thermotolerans and T. delbrueckii in different ratios, are available. To developsuch products, the understanding of genetic and phenotypic characteristics of strains andinteractions amongst the different organisms is important. Consequently, some studies haveinvestigated yeast-yeast interactions and their mechanisms, such as antagonistic interactionsmediated by direct cell contact or through growth inhibitory metabolites. This, results in adecline of certain non-Saccharomyces like Hanseniaspora and therefore effect the final aromacomposition. Conversely, synergistic effects can be observed in which species may bepromoted to persist longer and therefore they contribute more to aroma. However, knowledgeon population dynamics in multi-species starter cultures and their influence on alcoholicfermentation (AF) and MLF remains limited.The current study investigated a multi-species yeast consortium during AF and itseffects on Oenococcus oeni viability during MLF. The consortium comprised of M. pulcherrima,L. thermotolerans, T. delbrueckii and S. cerevisiae. Fermentations were conducted in Cheninblanc and Pinotage at 15°C and 25°C, respectively. In all trials M. pulcherrima declined rapidly,while L. thermotolerans persisted until mid-fermentation. The best growth was observed forT. delbrueckii and it was able to persist until late fermentation stages. Fermentations thatcontained L. thermotolerans produced L-lactic acid in the Pinotage, but not in the Chenin blanc.There were no negative impacts observed on O. oeni populations during MLF for Pinotageand Chenin blanc wines. MLF kinetics were similar in all the Pinotage wines. In the Cheninblanc, the fastest L- malic acid consumption was displayed in wines that were fermented byL. thermotolerans and T. delbrueckii co-inoculations with S. cerevisiae. Different chemicalprofiles were detected using attenuated total reflection infrared (ATR-IR) spectroscopy. MostlyChenin blanc wines were found to be significantly different from S. cerevisiae controls. Usinggas chromatography, fold changes were observed for many volatile compounds.In conclusion, it is possible to predict a consortium population dynamic based onindividual yeast performances in mixed fermentations. The volatile profiles are not additivebetween treatments and will be unique for each inoculation scheme. MLF seems to not be detrimentally affected by a consortium so long as each strain is regarded as compatible withlactic acid bacteria. Future work should include the evaluation of more yeast species and atalternate inoculation levels. Additionally, the inclusion of Lactobacillus plantarum for MLFneeds to be investigated and quantification of detected volatiles should be performed.

[发布机构] Stellenbosch University