Natural protection from oxidation in white and rosé winemaking 2021
The development of a potent antioxidant to protect musts in the prefermentative stages
Sieczkowski Nathalie, Lallemand Oenology
White and rosé winemaking requires special attention to the risks associated with oxidative phenomena. Color and aroma are parameters of fundamental importance in defining quality and freshness of these types of wine, and oxidative stability is therefore the focus of attention of winemakers, especially in the current context of limiting chemical inputs, particularly sulfites.
In this context, the world of Research was first directed to a better understanding of oxidative mechanisms and then to the development of new natural tools for improving the longevity of wines, from ‘aging to bottling.
Among them, a very recent research work conducted in collaboration with the IUVV in Dijon has led to the development of a new inactivated yeast specifically for the protection of musts and wines from oxidation.
The use of a new production process optimized for the biosynthesis and intracellular accumulation of reduced glutathione and the identification of a new strain of Saccharomyces cerevisiae with unique characteristics allowed us to arrive at the new specific inactivated yeast Glutastar™.
Metabolomic characterization confirmed the unique and specific composition of this new inactive yeast and its efficacy in application on wine compared with other inactive yeasts. In addition to its high content in reduced glutathione, the presence of peptides with reducing power increases its positive impact on the oxidative stability of wine.
The numerous trials conducted and the results obtained confirmed that early addition with this specific inactive yeast before alcoholic fermentation (in the press, at the press outlet or in prefermentative maceration) is effective in protecting the aromas and color of wines even after bottling.
Bioprotection with an innovative oxygen-consuming Metschnikowia
Gerbaux Vincent, IFV Institut Français de la Vigne et du Vin
The pre-fermentation phase, especially in white winemaking, concentrates the oenological operations that most favor oxidative phenomena and the development of contaminating microorganisms. The traditional use of sulfitation makes it possible to reduce these problems, but the current trend is to move toward a reduction in its dosage, or even its elimination. Thus, the risk of losing control of the pre-fermentation stage becomes increasingly real. Why not consider bioprotection with non-fermentative yeast flora an alternative and innovative solution? The IFV has selected Metschnikowia pulcherrima strain LCH15.21 (Level2 InitiaTM ) from a collection of more than 500 yeast strains isolated from grapes and musts. This yeast is able to colonize must without fermenting or producing undesirable compounds. Inoculation can be done at the time of crushing or at the time of mechanical harvest.
In several comparison trials, dissolved oxygen monitoring of pasteurized white musts incubated at 12°C shows a similar increase between control and sulfited wines at 50 mg/L reaching a plateau at 9 and 8 mg/L, respectively. In the case of using Metschnikowia LCH15.21 for bioprotection, a high consumption of dissolved oxygen was observed reaching insignificant levels in a few hours. Undesirable oxidative, enzymatic and microbiological phenomena were sustainably inhibited. Through further practical experience, José Maria Heras, will illustrate the dominant effect on indigenous flora, the effectiveness on copper reduction and the resulting positive effects of yeast on wine quality.
This new possibility of bioprotection allows greater freedom in the management of the prefermentative phase while also allowing for good aromatic expression. The use of this yeast during cold settling can be a significant technical advantage.
Preserving the freshness and longevity of wines during post alcoholic fermentation stages
José-Maria Heras, Lallemand Oenology
In the period between the end of alcoholic fermentation and bottling, wine is subject to oxidative phenomena. Oxygen ingress can vary depending on the operation, and normally sulfur dioxide is the most commonly used tool to prevent oxidation in finished wines. An alternative may be to store the wine on the lees of the yeast that conducted the fermentation but there are numerous risks associated with this choice (microbial contamination, quality of the lees, etc.). To overcome this problem, inactive yeasts of controlled quality can be chosen to be safely added to the wine. In particular, research conducted by INRAE (JM. Salmon) showed the ability of a specific inactivated yeast to consume dissolved oxygen and protect wine from oxidation. During the experiment, several different inactivated yeasts, obtained from both different yeast strains and different inactivation processes, were tested and their ability to consume O2 was measured.
One of these has proven to be the best in both the amount and rate of dissolved oxygen consumption, protecting the wine from oxidation during the various post-fermentation stages up to bottling.
With the aim of evaluating its many benefits, numerous application trials have been conducted in white wines (in racking, during storage, cold stabilization and transportation) that have highlighted the effectiveness and potential of this natural tool in preventing oxidation from the end of alcoholic fermentation.
