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Inactive yeast with guaranteed glutathione content.
Reduced GSH value >10%.
25-30 g/hl at the beginning of fermentation in order to bring several benefits:
Dissolve the product in 10 parts water, stirring continuously until completely homogenized. Ensure the absence of lumps and add to the mass to be treated.
1 kg bag.
Store in a cool, dry place, away from light or heat sources.
Inactive yeast with guaranteed glutathione content.
Reduced GSH value >10%.
25-30 g/hl at the beginning of fermentation in order to bring several benefits:
Dissolve the product in 10 parts water, stirring continuously until completely homogenized. Ensure the absence of lumps and add to the mass to be treated.
1 kg bag.
Store in a cool, dry place, away from light or heat sources.
to carry out fermentation with a non-Saccharomyces yeast, which will allow a low need for sulfur dioxide from the earliest stages
Dry inactive yeast (IDY) preparations are widely used in wine production. These products are obtained by cultivating Saccharomyces cerevisiae yeasts in a sugar substrate, followed by autolysis and subsequent drying to produce a powder. Depending on their composition, IDY preparations are used for specific purposes, such as improving alcoholic and malolactic fermentation processes or intensifying wine aroma and color.
The formulation that essedielle has developed is based on IDY with a high glutathione content (OxiFree G) and has shown excellent ability to protect aroma and color of white wines during aging, due to the higher concentration of glutathione (GSH) compared to other variants of IDY.
Glutathione is an intracellular tripeptide composed of L-glutamyl-L-cysteinyl-glycine, known for its antioxidant properties. During the winemaking process, GSH acts by preventing oxidative browning and preserving aromatic compounds, reducing the formation of undesirable flavors.
The mechanism of action of glutathione is based on its reaction with o-quinones derived from the oxidation of phenolic substances, leading to the formation of the product GRP (2-S glutathionyl kaftaric acid), which prevents the progress of oxidative reactions in must and wine (Cheynier et al. 1990). Despite its demonstrated efficacy, the direct addition of GSH to wine is not currently approved by the Organisation Internationale de la Vigne et du Vin (OIV). However, the use of OxiFree G represents an alternative strategy to increase GSH content in musts and wines.
essedielle thus developed several tests aimed at measuring the antioxidant power of its yeast derivative containing a concentration greater than 7% GSH. The measurements were supported using the WAT (Wine Antioxidant Test) system from the company DNAPhone srl (developed in collaboration with the DAGRI department of the University of Florence and the company H&D srl), an innovative method for quantifying antioxidant capacity in terms of mg/L of ascorbic acid equivalent, thus allowing the effectiveness of various antioxidants to be compared.
The WAT system measures antioxidant capacity, suffering no interference from sulfur and GSH (Sofia Pasqualini et al. 2023).
Because of this characteristic, we performed an indirect measurement of the antioxidant capacity of the two products by analyzing the amount of oxidizable species present in the wine samples over time.
A higher WAT value indicates a greater ability of the compound to prevent oxidation and, consequently, to protect oxygen-sensitive species present in wine, such as polyphenols and volatile aromas.
Three must samples treated in three different routes and named: Sample 1 (25 g/hl OxiFree G); Sample 2 (7 g/hl potassium metabolisulfite) and Sample 0 (control with no addition) were analyzed in the study.
The treatment was first carried out at the beginning of alcoholic fermentation, and we noticed how the amount of GSH released varies depending on the time of addition, thus affecting the availability of GSH at later stages of winemaking. Our studies show that reduced GSH tends to oxidize rapidly, limiting its presence in the wine (data not shown).
We can speculate that one of the processes that could influence the concentration of GSH in wine is the formation of GRP. Inactivated yeasts with guaranteed glutathione content, containing tripeptides with antioxidant potential, could stabilize GRP formation (Rodríguez-Bencomo et al. 2014).
In general, the concentration of GSH at the end of fermentation is too low to exert a significant antioxidant effect. Various factors, such as the low amount of GSH released, the redox balance of the must, and the utilization of GSH by yeast as a nitrogen source, may explain this result.
This finding prompted us to conduct further studies to optimize the use of yeast derivatives during winemaking, with the aim of fully exploiting their potential as antioxidant agents in wines.
We then proceeded to add our new product OxiFree G, along with potassium metabisulfite, at the beginning of alcoholic fermentation. This timing allows the yeast to better assimilate the nutrients provided by the GSH-enriched yeast derivative, such as amino acids and peptides, which stimulate glutathione synthesis and release.
Until recently, sulfur dioxide was the only solution used to prevent browning in musts because of its antioxidant, antioxidase and antimicrobial properties. However, the current oenological trend is toward reducing or eliminating the use of this additive because of its potential negative health and environmental effects.
The experiments conducted show us that the addition of sulfur dioxide does reduce the rate of oxygen consumption in the must, confirming its protective role against enzymatic oxidation, while in Sample 1 the addition of glutathione-rich inactivated yeast led to a greater reduction in oxygen consumption, attributable to the ability of glutathione to react with orthoquinones, reducing the availability of substrates for polyphenol oxidases (fig.1 and 2) (Singleton et al. 1985).
Fig. 1 Evolution of catechin content in the samples during the course of the test
Fig.2 Evolution of browning in the solutions throughout the duration of the test
To confirm this, we can also make use of the WAT value, which was found to be higher than that obtained with the addition of sulfur dioxide (Fig. 3).
It is important to make a small note regarding the WAT value of the control sample: the must came from a social winery that, due to handling large volumes of grapes, performs initial sulfitation during the winemaking process. This aspect is crucial, as the preliminary treatment affects the levels of residual sulfur in the must and, consequently, the WAT value, making it generally higher.
In our specific case, having conducted the laboratory tests on a small scale, we had to use this already pretreated must, which inevitably contributed to the increase in the observed value, compared to what would have been obtained in the absence of sulfitation. This aspect must be taken into account in the overall evaluation of the results.
Fig. 3 Antioxidant potency measured at the end of fermentation of the different samples taken for analysis
At 10 days after bottling (Fig. 4), the value for the sample treated with potassium metabisulfite is significantly higher. This is due to the powerful effect of sulfur dioxide, known for its ability to act as an antioxidant and preservative in biological systems (Renouf, Strehaino and Lonvaud-Funel, 2008). However, it should be noted that the effect of sulfur dioxide is transient and tends to diminish over time due to its volatility and reactivity with other compounds in the matrix. It is important to consider that we cannot accurately determine whether this value represents the fraction of free sulfur or bound sulfur.
In comparison, the second value associated with the OxiFree G sample is lower (Fig. 4), despite having a lower catechin index and coloring index than the sulfurose (Figs. 1 and 2). This could be explained by the fact that the scavenging activities of glutathione against °OH can react with free NH₂ amine groups, forming stable macromolecular radicals, and thus manifesting an adsorption effect of catechin and its colorless oxidation intermediates. This mechanism could be further investigated with further tests.
Fig. 4 Antioxidant potency measured 10 days after the bottling date of the different samples taken for analysis
While sulfur dioxide offers a strong but short-lived initial effect, glutathione proves to be a more stable and potentially more effective antioxidant in the long term, as it protects the system more consistently. In addition, the possibility of modulating the effect by increasing the concentration of yeast derivative use opens up interesting prospects for improving the oxidative stability of the product. Therefore, based on the available data, we can conclude that the use of OxiFree G appears to be a more promising choice, especially when considering a long-lasting antioxidant effect and continuous protection of the organoleptic and biochemical properties of the sample, avoiding the use of allergens.
With these aspects confirmed, we can confidently state the effectiveness of OxiFree G in the early stages of fermentation or at one-third of the process, as a natural and more sustainable alternative to sulfur dioxide for antioxidant protection in wines, ensuring better preservation of aromas and color in the long term.
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