Fermentation characteristics of non-Saccharomyces wine yeasts

V vinarstvu je trenutno kot starterska kultura najbolj priljubljena vrsta kvasovk Saccharomyces cerevisiae. Njena glavna prednost je predvsem sposobnost zaključiti alkoholno fermentacijo, brez zaustavitve in tvorbe neželenih metabolitov. Vse bolj pa postaja zanimiva uporaba ne-Saccharomyces kvasovk, ki sodijo v rodove Torulaspora, Lachancea, Metschnikowia, Hanseniaspora, Pichia, in Starmerella, ki tvorijo številne sekundarne metabolne produkte, s katerimi se izboljša kakovost in kompleksnost vina. Zanimive so tudi za pridelavo alkoholno manj bogatih vin. Da ne bi prišlo do zaustavitev fermentacije, smo proučevali, kako vpliva dodatek različnih ne-Saccharomyces kvasovk v kombinaciji s S. cerevisiae na potek alkoholne fermentacije mošta in na številne lastnosti tako pridelanih mladih vin (tehnološke, aromatične, metabolne). Uporabili smo komercialno dostopne starterske kulture ne-Saccharomyces kvasovk, poznane pod imeni Biodiva (Torulaspora delbrueckii), Laktia (Lachancea thermotolerans) in Flavia (Metschnikowia pulcherrima). Pri tem smo prišli do zaključka, da imajo tako pridelana vina kompleksen aromatičen profil na račun bolj izražene sortne arome ter tvorbe številnih estrov in višjih alkoholov. Vzorci so vsebovali v povprečju 7,64 g/L glicerola (literatura navaja razpon med 5 in 14 g/L glicerola). Vzorec z dodatkom Laktie, ki tvori mlečno kislino, je imel po pričakovanjih, nižji pH (3,3) in večjo skupno kislost kot drugi vzorci, vendar pa je bil po Buxbaumovi metodi ocenjen najslabše. Kot edini vzorec je sodil v kategorijo namiznih vin z geografsko oznako oz. deželno vino PGO, ostali vzorci pa v kategorijo kakovostnih vin z zaščitenim geografskim poreklom oz. kakovostno vino ZGP. Tekom fermentacije ni prišlo do zaustavitev, v splošnem pa so hitreje in višjo hitrost dosegali vzorci z naknadnim dodatkom S. cerevisiae.Nowadays most commonly used starter culture in winemaking is yeast strain Saccharomyces cerevisiae. Its main advantage is ability to complete alcoholic fermentation process without unnecessary halts and formation of unwanted fermentation products. However, it is becoming more and more interesting to use other non-Saccharomyces yeast strains of genera Hanseniaspora, Pichia, Starmerella, Torulaspora, Meschnikowia, Lachancea, forming numerous secondary metabolic products that improve wine’s quality and complexity. Aforementioned strains are also interesting for the production of less alcohol-rich wines. In order to avoid stuck or sluggish fermentations, we studied impact of addition of various non-Saccharomyces yeast strains in combination with S. cerevisiae on the course of alcoholic fermentation of must and many characteristics of thus produced young wines (technological, aromatic, metabolic characteristics). We used commercially available starter cultures of non-Saccharomyces yeast strains, known by their commercial names Biodiva (Torulaspora delbrueckii), Laktia (Lachancea thermotolerans), and Flavia (Metschnikowia pulcherrima). Wines produced in such manner had a more complex aromatic profile due to a more pronounced varietal aroma and presence of many esters and higher alcohols. Samples contained an average of 7,64 g/L glycerol (literature ranges of glycerol content between 5 and 14 g/L). As expected the wine sample fermented by lactic acid producing Laktia starter, had lower pH value (3.3) and higher total acidity that other samples, but received lowest scores according to Buxbauman method of sensory analysis. As the sole sample, it was categorized to the table wine category with the geographical indication or regional wine with protected geographical indication (PGI). The rest of the wine samples were categorized as quality wines with protected geographical origin (PGO). There were no halts during fermentation process. We have also noted that wine samples, in which yeast strain S. cerevisiae was added later, completed the process faster and at higher fermentation rate