Determination of hydroxytyrosol produced by winemaking yeasts during alcoholic fermentation using a validated UHPLC-HRMS method

Hydroxytyrosol (HT) is a phenolic compound of recognized bioactivity that has been described in wines but little is known about its origin. This work demonstrates that yeast involved in wine making, i.e. Saccharomyces cerevisiae strains and the non-Saccharomyces Torulaspora delbrueckii, can synthesise HT, as this compound was identified in the intracellular media of three strains by means of a developed and validated UHPLC-HRMS method with LOQ and LOD of 0.108 and 0.035 ng mL(-1) respectively. Controlled fermentations were performed with different varieties of grapes (Corredera, Moscatel, Chardonnay, Palomino fino, Sauvignon Blanc, Vijiriega, and Tempranillo) and synthetic must. The Saccharomyces cerevisiae strain QA23 was the most efficient producer of HT from tested yeasts. On the other hand, the grape variety influences HT wine concentrations. Furthermore, the maximum concentration of HT is reached between the fourth and sixth day of fermentation. This work reveals that yeasts have a great potential for the production of HT.