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Identifying Faults in Pinot Noir

I am sure you have experienced this disappointing scenario before. You pop the cork on a Pinot Noir, and as you smell the wine with eager anticipation, you immediately wrinkle your nose, wince, and begin to wonder what the heck you are smelling. Chances are, you are faced with a wine fault. Remember that chemistry class you hated in college? This discussion will bring back memories.

A wine fault or wine defect is an unpleasant characteristic of a wine primarily due to by-products of normal fermentation and the winemaking process. In small amounts, the characteristic can be an asset to some imbibers, but in larger amounts it becomes an unpleasant fault. The term “flaw” is sometimes used interchangeably with the word fault, but a flaw is better considered a more minor unpleasant characteristic. Whether a wine is considered to have a flaw, or even worse, a fault, will depend somewhat on individual tolerance for the character.

Unpleasant characters related to oxidation, reduction and sulfur dioxide often appear upon first opening a wine, but can dissipate or even disappear with exposure to air and swirling. A fault, however, will persist over time as an unfortunate component of the wine.

I have organized the most common unpleasant characters to ease identification and divided them into eight categories. All categories are a by-product of fermentation or secondary to the winemaking process except cork taint (listed last). At the end, I have simplified identification even further and you may want to print this out for quick reference.

    (1) Oxidation This class of aromas are consequences of fermentation, resulting from the oxidation of ethanol and bacteria (Acetobacter) interacting with acetic acid and ethanol (bacterial spoilage). They are referred to as volatile acidity (VA) or acescense. The aromas include acetaldehyde (rotten apples, bruised apple, dry straw, sherry, staleness, nuttiness, or cooked or stewed fruit), acetic acid (vinegar or Easter egg dye), and ethyl acetate (nail polish remover or acetone, glue, wood varnish, or paint thinner). A nutty, bruised apple aroma is only considered desirable in oxidative wine styles such as sherry. Volatile acidity is found more often with wild yeast fermentations and higher sugar levels because when sugars are high, yeasts may struggle, leading to a stressed fermentation and elevated VA.

    (2) Reduction Aromas of volatile sulfur compounds are produced by yeasts during fermentation, and include hydrogen sulfide (rotten eggs, cabbage, rubber, burnt rubber, cowpat, human fart, sewer, cooked veggies or roast coffee) and thiols known as mercaptans (onion, garlic, flint or rubber). Collectively, these aromas are known as “reduction” or “bottle stink.”

    (3) Sulfites Distinctive from sulfides, sulfites are by-products of sulfur dioxide added to wine as a preservative and antimicrobial agent and may produce aromas of sulfur, struck or burnt match, flint and burnt rubber. Often a trace of sulfur dioxide may be noticed in a newly bottled wine or in a wine upon first opening. Every wine label is required to have the words “Contains Sulfites,” unless no significant sulfur dioxide is used (less than 20 parts per million) in vinification and can be labeled as “Organic Wine” if grapes are also organically grown.

    (4) Yeasts The many compounds produced by the yeast Brettanomyces bruxellensis (Brett for short) and its relative, Dekkera bruxullensis, produce distinctive aromas in bottled wine. Brett contamination leads to four main by-products: esterases from degradation of fruity esters that leads to loss of fruitiness, volatile fatty acids including acetic acid and ethyl acetate (aromas of vinegar and or acetone), volatile phenols including 4-ethyl guaiacol (aromas of smoke, smoked bacon, creosote, burnt beans, strong spice, BBQ, clove, or burnt wood) and 4-ethyl phenol (aromas of horse sweat, sweaty horse blanket, horse stable, wet dog, barnyard, fecal, band-aid, antiseptic, or medicinal) and tetrahyropyridines (aromas of bread, popcorn or cracker in low concentration and mousy or horsy in high concentration. The volatile phenols are compounds only produced by Brett. Still other descriptors for Brett include wet wool, chicken droppings, gamey, funky sock, rotting vegetation and mouse case. Brett is more common in wines with higher pH, higher alcohol and minimal sulfur dioxide usage.

    (5) Guaiacol Aromas of wet ashtray, burnt meat and smoke derive from guaiacol in grapes exposed to smoke or in wines aged in toasted barrels.

    (6) Barrel Aromas of clove (eugenol), nutmeg, cinnamon, vanillin and coconut (lactones) can derive from oak barrels. Long barrel aging can lead to sotolone, an aromatic molecule in maple syrup, caramel, toasted nuts and soy sauce.

    (7) Diacetyl This organic compound has a IUPAC systemic name of butanedione and is a by-product of malolactic fermentation. It has a buttery aroma in low concentrations and an oil, nutty, butterscotch or caramel aroma in higher concentrations.

    (8) Fungus Cork taint is caused by the chemical compounds, 2,4,6-trichlororanisole (TCA) or 2,4,6-tribromoanisole (TBA) in a bottled wine, in many cases transferred from the cork. The compounds are a by-product of the interaction of some fungi with chlorinated phenolic compounds used in the processing of wood such as cork. This fault is not due to a natural fermentation by-product. Typical aromas include wet or moldy newspaper, wet dog, damp cloth or damp basement. Individual sensitivity to cork taint varies widely.

Faults at a Glance for Chemistry Averse Winos

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