This wine defect, which usually occurs after alcoholic fermentation, can result from malolactic fermentation that has not proceeded correctly. Synonyms are butyric acid taint, yoghurt taint, whey taint and sour grape button. Because of the synonym butyric acid taint, it is often wrongly assumed that this is due to the butyric acid contained in the wine (see butyric acid fermentation). Uncontrolled acid fermentation can lead to infections with lactic acid bacteria of the Pediococcus and Lactobacillus genus. These produce the aroma substance diacetyle, which gives the unmistakable and typical buttery (lactic) or herbaceous note. The defect manifests itself in a typical slightly sweet and sour smell and taste of yoghurt, buttermilk, cheese or sauerkraut and thus also a milky cloudiness in the wine. Wines with low acidity and low tannin content and a high pH value are particularly at risk. Activated carbon is used to combat this wine defect. A quite similar wine defect is lindtone, which is also caused by lactic acid bacteria.
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Diplom-Sommelier, Weinakademiker und Weinberater, Volders (Österreich)