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A Technical Guide for Wine Producers
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RECENT ARTICLES | WYNBOER HOME
Using highly absorbent yeast hulls in wine for eliminating corked and mouldy taints
Olivier Fernandez, Céline Fauveau & Patrice Pellerin, DSM Food Specialties
Carole Puech, Patrick Vuchot & Stéphane Vidal, Inter Rhone
Cork and mouldy taints are defects currently occurring in wines. Today it has been established that these alterations are not only due to cork contamination but can also come from products used in treating wood, or hygiene chlorinated products.
In this paper, we look at the adsorbent properties of the yeast hulls developed by DSM Food Specialties in respect of the haloanisoles, molecules causing these defects. During the production process developed by DSM Food Specialties, Extraferm© hulls undergo a treatment that considerably increases their adsorption capacity. This process, guarantees that HALO (High Adsorption Low Odour) hulls are obtained, in other words, hulls that do not transfer any odour to the wines, even when high doses are used.
Chloroanisoles are the main cause of mouldy taints in wine, particularly 2, 4, 6-trichloroanisole (TCA), 2, 3, 4, 6-tetrachloroanisole (TeCA) and pentachloroanisole (PCA). TCA found in wine that is still in the tank, comes either from using chlorine based cleaning products, or from using humidifiers that are run using highly chlorinated water. On contact with phenols in wood, wine residues, or some types of polymer resin, chlorine reacts rapidly and forms trichlorophenol (TCP). Furthermore, many of the insecticides and fungicides used to treat wood (beams, palettes, doors and so on) contain tetra- and pentachlorophenol (TeCP and PCP). Moulds found in the winery then turn these TCP, TeCP and PCP into highly volatile TCA, TeCA or PCA.
Other molecules responsible for mouldy taints have been highlighted recently: Bromoanisoles, particularly 2, 4, 6-tribromoanisole (TBA). It can come from epoxy bromide resins varnishes (caps), or from fire retardants (tetrabromobisphenol) treated woods and wood chips. Like chloroanisoles, these precursors form volatile compounds with the action of moulds.
In all cases contamination is spread through the air in the winery.
These aerial contamination mechanisms are shown diagrammatically on Figure 1.
The effectiveness of Extraferm© in reducing haloanisoles, has been quantified in two stages, by laboratory trials, then by large volume trials.
In the Inter Rhone lab, trials were conducted on naturally contaminated wines, with TCA and TeCA contents over their perception thresholds (Table 1).
Large volume experiments in two wineries
The wines were treated with 40 g/hL of DSM yeast hulls with a contact time of 48 hours, homogenization was achieved by pumping over three times a day.
On the first site, two white wines had high levels of TBA (5.5 and 2.8 ng/L). The treatment reduced TBA to below the perception threshold (5 ng/L), down to 1.2 and 0.6 ng/L, (- 78 %) (Table 2). In addition, the TeCA was reduced from 2.6 to 2 ng/L (- 23 %) and PCA from 21.5 to 6.8 ng/L (- 68 %). The "residual" levels were below perception thresholds.
On the second site, a red wine had high levels of TeCA and PCA (60 and 147 ng/L). The reduction in TeCA and PCA was respectively of 60 and 61 %.
To summarize these results, molecules can be classified according to their ability to be adsorbed by yeast hulls (Figure 2). The increased number of chlorine atoms on the anisole nucleus increases molecular apolarity.
The large volume trials confirmed the effectiveness of the DSM HALO yeast hulls to treat wines contaminated by haloanisoles, this with a negligible effect on the composition of wines. After treatment, even at a maximal dose of 800 mg/L, no defect could be detected by the Inter Rhone Technical Service enologists.
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