Bioprotection and oenological tannins association to protect Rosé wine color

Abstract

The bioprotection of musts or grapes is a strategy for limiting sulfiting during winemaking and more specifically at pre-fermentative step. The most preconized yeasts in bioprotection mainly belong to Metschnikowia pulcherrima and Torulaspora delbrueckii species. While previous studies have demonstrated that bioprotectant non-Saccharomyces strains were able to protect musts and wines against microbial spoilage as well as sulfites, they cannot protect must against oxidation which appears to be the main limit of this practice.

A combination of antimicrobial activity through bioprotection (inoculation of a Metschnikowia pulcherrima strain on grapes) and the antioxidant properties of low amounts of sulfites or enological tannins have been tested in order to replace or diminish SO2 addition in rosé winemaking (grape variety Pinot Noir) at pre-fermentative steps. This experiment was carried out under cellar condition. Two enological tannins were tested: quebracho tannins belonging to the condensed tannins family and gall nuts tannins belonging to the hydrolysable gallotannins family. Results showed that combination of bioprotection with enological tannins protected rosé wine color similarly as the combination with SO2, which was not the case with bioprotection alone. The color differences observed cannot be explained neither by anthocyanins concentration, nor by phenolic composition of wines. Quebracho tannins seemed more efficient than gall nuts tannins to protect the color of bioprotected rosé wines.