Aromatic Defects in Wine

Wine Defects Defects Part I Defects Part II Acetaldehyde, oxidation Cork taint, TCA VA I, acetic acid Brettanomyces 1 VA II, ethyl acetate Brettanomyces 2 Lactic taint Methoxypyrazine Hydrogen sulfide Microbial

Oxidation Oxygen is essential for fermentation Beneficial during maturation in small quantities for most dry reds, some whites Over exposure of oxygen in must and wine results in Browning, general shift in color Loss of fruit characteristics Development of oxidized aromas and flavors Some wines however require excessive oxygen to develop their characteristic style. These include: ?

Acetaldehyde Causes During fermentation, acetaldehyde (CH3CHO) is a precursor to ethanol production Almost all is subsequently converted into ethanol (C2H5OH) Presence of acetaldehyde in a finished wine often indicates an excess of oxidation or spoilage caused by aerobic film yeast Impacts white wines more than reds Can be smelled in as small a quantity as 1.5 ppm Has a nutty, sherry like aroma May react with anthocyanin pigments to shift the red color towards blue Excessive SO2 at fermentation may contribute to its production

Oxidation and Acetaldehyde Prevention Moderate SO2 dose at fermentation and keep pH low Careful control over CO2 levels in white and reds following fermentation Minimize aeration during transfer (racking, bottling) by using inert gas (CO2, argon, nitrogen) ? Treatment

Volatile Acidity I – Acetic Acid Causes Volatile acidity will vaporize with steam heat unlike other acids present in wine. Acetic acid is almost always the result of bacteria Acetobacter require oxygen to survive and grow Causes of acetic acid may be from Exposure of must/cap to air during fermentation Unsanitary containers or containers infected with bacteria Initial high brix must followed by an incomplete fermentation Spoilage by lacto bacillus Over exposure during maturation Surface/film yeast on the wine Poor SO2 management

Volatile Acidity II – Ethyl Acetate Causes Ethyl acetate is an ester of ethyl alcohol and acetic acid Threshold sensory level for most people is 150–200 mg/L Acetobacter in the presence of oxygen may develop EA Causes of ethyl acetate may be from high levels of acetic acid due to Unsanitary fermentation containers and tools Poor fermentation technique – excessive exposure of must/cap to air during fermentation High pH and wines with little SO2 (acetobacter are sensitive to SO2 ) Stuck wines – wines with residual sugar Excessive exposure of wine to air during maturation. Lactic acid or acetic acid spoilage Sound wines will not generate VA once bottled.

Volatile Acidity (VA) I, II Treatment / Prevention ?

Lactic Taint Causes Lactic taint or souring Lactic bacteria other than ML bacteria metabolizing malic acid Lactobacillis and Pediococcus Malolactic fermentation, when undesirable in white wines Wine is often spritzy and turbid with odors such as Spoiled milk/buttermilk Sourdough Fermenting cabbage Excessive diacetyl, producing soured buttery aromas Sound wines may generate LT once bottled if residual malic acid is present.

Lactic Taint Prevention Strive for low pH and good SO2 management Proper hygiene, clean and/or pasteurized equipment Use lysozyme addition and/or sterile filtration to curtail or prevent ML fermentation Use fresh bacteria cultures from dependable sources if ML is desired. Monitor results Treatment, ?

Hydrogen Sulfide Not sulfite. Sulfide threshold is 5 ppb Hydrogen sulfide, mono and di-mercaptans As a flaw, may be mistaken for varietal or regional character “terroir.” Odors range from slightly complex aroma, rotted cabbage, tires, or sewage. Usually associated with stressed yeast and low nitrogen levels during fermentation. Causes include -- Free sulfur/late sulfur spray on grapes. Some yeast strains produce more than others but all yeast produce H2S. Insufficient nitrogen for fermentation Elemental sulfur inside barrels May become more complex, harder to treat as the wine ages

Hydrogen Sulfide Prevention Proper nutrients for yeast added at appropriate timing sequences before and during fermentation (Follow supplier’s recommendations) Use appropriate and healthy yeast strains Avoiding fruit with free sulfur-containing compounds Avoid heavy layer of sediment in wine containers Monitor wine throughout fermentation and maturation for sulfide odors and correct early

Hydrogen Sulfide Treatment – ? Concerns

Cork Taint As many as 10% of bottles may exhibit taint Cause – is the chemical compound, 2,4,6- trichloroanisole or TCA Produced by mold spores digesting phenol in the presence of chlorine used to clean raw cork TCA can occur/develop during manufacturing or in the cellar Prevention Never allow chlorine products in the winery Sample corks to screen for TCA Treatment There are a few costly proprietary processes (www.winetech.us) ?

Brettanomyces Causes Spoilage yeast, commonly found in wines, primarily reds Yeast are resistant to moderate levels of SO2, low alcohol Can feed off of small amounts of residual sugar in wine or present in the wood of a barrel (ideal environment) Odor and flavors may increase over time and may resemble horse stable, plastic, Bandaid ® (4-ethyl phenol) smoked bacon, spice or cloves sweaty animals, cheese and rancidity wet dog, creosote, burnt beans, rotting vegetation, mouse cage, mouse urine

Brettanomyces Causes Dominates or destroys the fruit of the wine In minute amounts may add complexity. “Brett” is a slow growing yeast that does not compete well against other micro-organisms. Second use (or older) oak barrels aid in its colonization Temperatures which encourage ML fermentation also aid in Brett to increase in population in the wine Dissolved oxygen from frequent topping off help this yeast grow Prevention Use only clean or new barrels Maintain hygiene and consistent SO2 management Treatment ?

Microbial Causes Generic yeast and bacteria spoilage of wine other than those mentioned Usually the result of Warm temperature of fruit arriving at the winery Contamination from unsanitary condition Low TA, high pH wines with residual sugar Warm environments with dissolved oxygen Retaining heavy lees following fermentation Inconsistent or improper SO2 management Residual sugar and or nutrients that support microbial growth Residual malic acid or protracted ML fermentation Prevention ? Treatment?

Methoxypyrazine Causes Commonly referred to as an overpowering, unpleasant vegetative odor in wine Light to moderate case: green bell pepper, fresh leaves Worst case: Crushed lady beetle odor Threshold of 10 to 15 parts per trillion¹ More common in cooler vintages or climates, lack of ripeness, physiologically immature, harsh tannins Levels seem to decrease with fruit ripening Typically levels do not decrease, degrade, with bottle aging More common in some varietals (sauvignon Blanc) than others Can also be attributed to crushed insects such as lady bugs 1. Roujou de Boubee, D., 2003 Amorim Academy Grand Prix

Methoxypyrazine Prevention Vineyard selection Vineyard management Neither too low nor high a cropping level (vine balance) Appropriate level of sun exposure in the canopy Vineyard management Decreasing water between fruit set and véraison Harvest management Avoid fruit with lady bugs Thoroughly inspect all fruit before it enters the crusher Treatment ?

Wine Defects – Notes Defect Source Characteristic Aroma Oxidation Oxygen VA I, Acetic Acid Biological VA II, Ethyl Acetate Lactic Taint Hydrogen Sulfide Sulfur Cork Taint Environ Brettanomyces I (Ethylphenol, 150 ppb) Brettanomyces II (Isovaleric acid) Microbial Methoxypyrazine