Improving the implantation of non-Saccharomyces yeasts in winemaking by UHPH processing

Abstract

The use of unconventional yeasts, also called non-Saccharomyces yeasts, is a hot topic in current enology due to the improvement that can be produced in the sensory profile during fermentation. However, the use of these yeasts have problems due to difficulties in the implantation and competition with wild Saccharomyces yeasts. Ultra-High Pressure Homogenization (UHPH) has demonstrated to be a powerful tool to eliminate microorganisms in grape must, specially yeast and bacteria even at low in-valve temperatures. UHPH can be considered a non-thermal technology with protective effect on sensitive molecules as terpenes and anthocyanins. The preprocessing of must by UHPH leaves it free of yeast with an optimal sensory quality, being this a perfect situation to inoculate non-Saccharomyces yeasts. We have fermented UHPH musts and controls with several non-Saccharomyces species (Lachancea thermotolerans, Metschnikowia pulcherrima, Torulaspora delbrueckii, Hanseniaspora vineae), reaching in most of the UHPH treatments better implantations of the inoculated yeasts and a complete elimination of wild yeasts. The impact of the UHPH treatment is a better expression of the metabolic and enzymatic activities of the non-Saccharomyces yeasts. That effect enhances the sensory quality and facilitates the use of non-Saccharomyces yeasts at industrial scale.