Читать книгу Wine Faults and Flaws - Keith Grainger - Страница 65

Any deposits in the glass should be noted. These may comprise tannin sediments (which are simply the coagulation of phenolic substances) in the case of red wines or tartrate crystals in either reds or whites. Phenolic sediments naturally occur in fine red wines following bottle maturation, and such wines should be decanted before service. Although some might disagree, tartrate crystals should not be regarded as a wine fault, and are often visible in wines of the very highest quality. Thick deposits in red wines may also be tannin‐stained tartrate deposits (especially in low pH wines). However, in white wines, they can look alarmingly like pieces of broken glass and worry the consumer, but they are completely harmless. The crystals are most likely a precipitate of potassium bitartrate (KC₄H₅O₆) or occasionally calcium tartrate (C₄H₄CaO₆). They are often found in bottles of German or other wines that have a high level of tartaric acid. They may precipitate if the wine is subjected to cold conditions – perhaps in a cold cellar or refrigerator. Many winemakers go to great lengths to try to ensure that the crystals do not appear in the bottle. This topic is discussed in detail in Chapter 15. The money and time spent by the industry on such treatments might be better invested in consumer wine education.

Grey or pale brown deposits are certainly a warning sign – they are most likely to be dead yeast cells or bacteria. Whilst it is possible that these are a consequence of inadequate racking and filtration, they are more likely an indication that the wine has undergone an alcoholic or MLF in the bottle, as discussed in Chapter 9. In any event, the aroma and flavour profiles together with the texture, will have been modified.