Does bioprotection by adding yeasts present antioxydant properties?

Abstract

AIM: The bioprotection by adding yeasts is an emerging sulfur dioxide alternative. Sulfur dioxide is a chemical adjuvant used for its antiseptic, antioxidasic and antioxidant properties. Faced with the societal demand (Pérès et al., 2018) and considering the proven human risks associated with the total doses of sulfur dioxide (SO₂) present in food requirements (García‐Gavín et al., 2012), the reduction of this chemical input is undeniable. Bioprotection allows the control of microbial communities by occupying the grape must niche (Simonin et al., 2018; Windholtz et al., 2021), but no studies have been conducted on its antioxidant properties. Indeed, in must, reaction cascades can take place, bringing into play different compounds that can lead to its undesired browning under the action of polyphenols oxydases. SO₂ neutralizes these enzymes and regenerates the quinones. In the present study, bioprotection have been considered for its action on oxidation and on the availability of dissolved oxygen (O₂).

METHODS: In order to evaluate the potential impact of bioprotection on dissolved O₂ content, an experiment was conducted using semillon must. Three treatments were applicated: SO₂ at 50 mg/L, without SO₂ and bioprotection composed of two yeast species (Torulaspora delbrueckii and Metschnikowia pulcherrima in the same proportion) at 50 mg/L. O₂ concentration was monitored during pre-fermentation phase, using a FireStingO2 compact oximeter (pyroscience, Aix-La-Chappelle, Allemagne). The glutathione, a natural antioxydant compound, was quantified in the musts and wines.

RESULTS: Based on dissolved O₂ kinetics, the use of bioprotection led to a rapid consumption of O₂ and limited browning comparing to the control, without SO₂. The addition of SO_2,by neutralizing the polyphenol oxydases (Ough and Crowell, 1987), also limited the O₂ consumption. Bioprotection treatment allowed obtaining a significant higher concentration of glutathione in the finished wines than the control without SO₂, thus allowing an interesting additional protection during bottle aging.

CONCLUSIONS:

For the first time, this work highlighted the limitation of the white must oxidation by using non-Saccharomyces yeasts as bioprotection in a context of without SO₂. By decreasing the availability of dissolved oxygen, bioprotection by adding yeast would slowing down the oxidation cascades. Furthermore, preservation of glutathione by bioprotection allows additional protection in wines.