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Bioprotection in oenology

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Thursday 20 May

Bioprotection: a low-sulphites winemaking tool

Sara Windholtz, University of Bordeaux

Chemical preservatives in agri-food products are source of controversy, and oenology is no exception, especially with sulfur dioxide (SO2). This additive has been used for many years during the winemaking process for its antimicrobial, antioxidant and antioxydasic properties. Facing social expectations and rule evolution, winemakers are committed to produce wines with low sulfite or even zero sulfite contents. A low-sulphites winemaking remains a risky decision, and its consequences on the fermentation process, the chemical and sensory characteristics remain poorly explored. The inoculum with non-Saccharomyces strains as a bioprotection agent is currently considered as an alternative to the first sulfiting.

The objectives of this presentation are to discuss the consequences of using bioprotection, on the microbial diversity of prefermentary, as well as on the chemical and sensory composition of wines.

The two species used in bioprotection, Torulaspora delbrueckii and to a lower extent Metschnikowia pulcherrima, colonize the grape must during the prefermentary stages, with a decrease of the relative abundances of fungal communities in comparison with the control without SO2, due probably to phenomena of competition to occupy the environment.

Moreover, bioprotection consume oxygen in the grape must, which allows partial protection against oxidation and at the same time limiting acetic bacteria development.

Finally, the early use of non-Saccharomyces yeasts in bioprotection significantly changes the chemical characteristics of wines with an increase of the fruity character of young wines at the sensory level, which nevertheless remains limited if compared to the use of the same strains in mixed fermentation with S. cerevisiae.

 

 

Two BIOprotection solutions for application on grape harvesting equipment and in liquid cold storage.

Julie Barthoux, Biolaffort

A formulation of strains of the Torulaspora delbrueckii and Metschnikowia pulcherrima species sourced from eco-selections for BIOprotection. These strains selected from among the grape’s indigenous flora for their organoleptic neutrality will colonise the medium and control the microflora in the pre-fermentation stages. Combining these two high-implantation-capacity species (equipment) and more SO2 -resistant (Torulaspora) and the other, particularly healthy during grape inoculation (Metschnikowia), ensures that the medium is protected by micro-organisms producing positive results in a wide range of circumstances. This formulation is particularly suitable for winemaking process with sulphur reduction.

Metschnikowia pulcherrima strain resulting from mass selection for BIOprotection. ZYMAFLORE® KHIOMP was selected from indigenous grape flora (from cold stabulation must in Provence South of France) for its ability to colonise the medium at low temperature and during long pre-fermentation phases.