WINE FAULTS

Mousiness is a wine fault most often attributed to Brettanomyces but can also originate from L. brevis, L. fermentum, and L. hilgardii (Du Toit and Pretorius 2000). The metabolism of ornithine and lysine is associated with the formation of N-heterocycles, 2-acetyl-1-pyrrolene, 2-acetyltetrahydropyridine and... 

Modern advances in hygiene has eliminated many of the bacterial concerns that contribute to wine stability. Historically the presence of bacteria played a larger role in the developing of various wine faults. The primary concern in modem wineries is the presence of acetobacter which can turn wine into vinegar and lactic acid bacteria that can initiate malolactic fermentation which may not be desirable for certain wines. 

To define the shade or tint of color, Sudraud (45) recommends using the ratio of the absorptions at 420 and 520 nm. These two indexes may be faulted for being conventional and for not defining the color in absolute terms, but they are a true advantage because they allow the wines to be compared among themselves in several processes (vinification, storage, aging). This is why tristimulus method seems to us to be an unnecessary complication, even in the simplified form recommended by the International Office of Wine and Vine (1962). 

To ascertain if the wine is normal or has undergone alterations owing to defects in the prime materials employed (grapes turned bad, or unripe, or attacked by parasites, etc.), or to faults in the manufacture or storage. In this case, besides the objective and microscopic examinations, use is also made, where necessary, of determinations of the normal components of wine as in case (c). 

Hilgard also preached temperance and the importance of wine quality. His famous letter (7) to William Randolph Hearst on what was wrong with the industry was published in the San Francisco Examiner of August 8,1889. In answer to the question What do you consider the cause of the present depression in the wine market he wrote Chiefly and fundamentally, the poor quality of the larger part of the wines made, and their immaturity when put on the market. It is high time that the ostrich-like policy of hiding the faults of our winemaking from ourselves were done away with once for all. ... 

Phenolic compounds play a vital role in the flavor of red wines. They are responsible for some positive tasting characteristics, but also for some rather unpleasant, negative aspects. Body, backbone, structure, fullness and roundness are all organoleptic qualities characteristic of great red wines. On the other hand, bitterness, roughness, harshness, astringency and thinness are faults that must be avoided as they are incompatible with quality. 

It should be emphasized, however, that barrel aging alone cannot be expected to produce high-quality wine. Wood is capable of enhancing a wine s intrinsic qualities and may hide certain faults. Used unwisely, barrel aging may produce disastrous results. 

Acetic acid is found in most people s homes as the active component of vinegar. It is also produced in improperly stored wines. The word vinegar originates from the French vin aigre, which means "sour wine." The presence of vinegar in wines is considered a serious fault, making the wine taste like salad dressing. 

This fault is associated with wines rather than musts because synthesis of these compounds requires the presence of ethanol (Heresztyn, 1986). As the aroma threshold in wine is very low, 1.6(lg/L (Riesen, 1992), very little growth of these bacteria is required to potentially spoil a wine. Sponholz (1993) suggested that mousiness is not a common problem, but low-acid wines with insufficient SO2 can be more prone to spoilage. Lay (2003) reported that different cultures of Brettanomyces formed a distinctive mousy taint in the presence of lysine or ammonium phosphate under both aerobic and anaerobic conditions. 

In low-acid, dry wines, growth of pediococci and lactobacilli may result in formation of extracellular polysaccharides. Many appear to be P-D-glucans (Llauberes et al., 1990) but other monosaccharides may be present (Manca de Nadra and Strasser de Saad, 1995). Described as ropi-ness or oiliness by winemakers, this fault is commonly detected as an increase in viscosity. 

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