WINETECH Technical Yearbook 2021

fraction, removal of spoilage compounds and blending. Potential problem wines must be sold as soon as possible, because the spoilage compounds can become more evident during maturation. Winemakers have to make certain decisions regarding the handling of smoke-spoiled grapes and wine. Less than 100 out of thousands of compounds, which occur in wine, are as- sociated with this spoilage. Structurally some of these compounds are the same as desirable wine compounds. Glycosides occur generally in wine and act as reservoirs for non-aromatic com- pounds, which can over time set aromatic compounds and glucose free. If this release is not floral compounds, the wine is unac - ceptable. Vines however use a protection mechanism to prevent the toxicity of the free spoilage compounds through seques- tering of the free compounds. Wines that can potentially exhibit smoke spoilage can be treated in different ways. The magnitude of exposure will influence

the decision making. Grapes with much exposure must preferably be whole bunch pressed. The duration of juice contact with undissolved grape material must be limited to prevent the dissolving of smoke spoilage compounds in the juice. Free-run fractions must preferably be separated from press fractions. Research on the influence of fining agents on the removal of smoke spoilage compounds from wine found that only activated carbon and synthetic mineral products decrease the concentration of the compounds, as opposed to egg albumen, K-caseinate, isinglass, bentonite, PVPP, gelatine and yeast cell walls. Different activated charcoal products however differ regarding their influence. Activated charcoal products were developed to selectively remove the phenolic compounds that are associated with smoke spoilage, from juice. One of these products is also more effective to remove 4-ethylphenol and 4-ethylguaiacol from wine.

If only the free smoke spoilage compounds have to be removed, the solution is much easier. The phenols that are however bound as glycol-compounds and are only released at a later stage, must also be removed. Different companies developed equipment for that purpose. It comprises the use of membrane equipment to separate the compounds using their molecular weight. The application of different combinations of differential filtration, ultrafiltration and membrane separation is required for this process. Spinning cone equipment can also be used to remove bound smoke spoilage compounds from wine (Carey, 2021). Flash détente is a technique to extract more colour and tannins from red grapes. It consequently contributes to a fuller structure of the wine. It is suspected that it can diminish the perceptibility of smoke spoilage. The possibility however also consists that the increased temperature can cause the increased extraction of more smoke spoilage compounds. A trial with Cabernet Sauvignon indicated the following:

• The concentration of free guaiacols was diminished by a 53% average. • The concentration of total guaiacols was however diminished by only 12%. The total guaiacol concentration was consequently not increased by it. • The aroma of treated wine was improved, but the smoke taint was not removed completely. • More emphasis should be placed on the diminishing of the bound guaiacols. (Lasky, 2021.) REFERENCES Carey, R., 2021. Grapes, wine and smoke taint. Wine Business Monthly , January 2021: 98-110. Lasky, M.S., 2021. Winemaker trial: Flash détente as a mitigation technique for smoke- exposed grapes. Wine Business Monthly , January 2021: 112-115.

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