UNDERSTANDING FAULTS IN WINE BY JAMIE GOODE

Transcription

1 FLAWLESS UNDERSTANDING FAULTS IN WINE BY JAMIE GOODE

2 Contents Table 1 3 Table 2 4 Table 3 5 Table 4 8

3 table 1 Percentage of SO 2 in the Molecular Form at Different ph Levels ph Molecular SO

4 table 2 Some Compounds Produced by Brettanomyces Compound 4-Ethylphenol 4-Ethylguaiacol Isovaleric acid 4-Ethylcatechol 2-Phenylethanol Guaiacol Ethyldecanoate Trans-2-nonenal Isoamyl alcohol Ethyl-2-methylbutyrate Sensory impact Band-Aid, medicinal, phenolic, horsey Spicy, smoky, phenolic, cloves Sweaty, rancid, cheesey Medicinal, stables Honey, spice, lilac Smoky Fruity, appley, waxy Green, fatty Unpleasant Fruity, peachy, appley 4

5 table 3 Some of the Key Volatile Sulfur Compounds in Wine Name a Sensory descriptor Perception threshold Comments Hydrogen sulfide (H 2 S) Rotten eggs, drains 1 mg/l What we normally think of as reduction. Produced by yeasts during fermentation in varying amounts. Dimethyl sulfide (DMS) Canned corn, cooked cabbage, asparagus 3-Mercaptohexyl acetate (3MHA) Grapefruit zest, [3-sulfanylhexyl acetate] passionfruit (R enantiomer); 3-Mercaptohexan-1-ol (3MH) [3-sulfanylhexan-1-ol] more herbaceous, boxwood (S enantiomer) Passionfruit (S enantiomer); grapefruit (R enantiomer) 25 μg/l Enhances fruity flavors in young red wines and can contribute truffle characters to older wines. 9 ng/l (R); 2.5 ng/l (S) 60 ng/l (S); 50 ng/l (R) Very important in the fruity aroma of Marlborough Sauvignon Blanc. During aging of wine, this hydrolyzes to 3MH. Always present in Sauvignon Blanc, at concentrations ranging from several hundred ng/l to as high as mg/l. Wines with highest levels of 3MH tend to have the highest levels of 3MHA. (continued) 5

6 table 3 (continued) Name a Sensory descriptor Perception threshold Comments 4-Mercapto-4-methylpentan-2-one (4MMP) [4-methyl-4-sulfanylpentan-2-one] 3-Mercapto-3-methylbutan-1-ol (3MMB) 4-Methyl-4-mercaptopentan-2-ol (4MMPOH) 2-Furanmethanethiol (also known as 2-furfurylthiol or 2-furfurylmethyl mercaptan) Box tree, broom 0.8 ng/l Present at up to 100 ng/l in fresh box leaves; can be found at up to 40 ng/l in some Sauvignon Blancs. Cooked leeks 1,500 ng/l Rarely found in wine above perception threshold. Citrus zest 55 ng/l (20 ng/l in water) Roasted coffee 0.4 ng/l Identified in sweet whites from Petit Manseng variety and red Bordeaux wines and has been found in toasted oak. Also found in Champagne aroma. Ethyl-3-mercaptoproprionate Meaty Found in the aroma of Champagne. 4-Methyl-4-mercaptopentan-2-ol Citrus zest 55 ng/l Rarely found in wine above perception threshold. 6

7 Methanethiol (methyl mercaptan) Rotten cabbage, stagnant water Ethanethiol ( = ethyl mercaptan) Rotten onion, burnt rubber at threshold levels; skunky or fecal at higher levels 2-Mercaptoethanol Barnyard Ethanedithiol Rubber, rotten cabbage Benzenemethanethiol (also known as phenylmethanethiol and benzylmercaptan) Gunfl int, fl int, struck match, smoky 1.5 ng/l 1.1 ng/l 0.3 ng/l Potentially responsible for reductive aromas in some wines. Found as a component of Champagne aroma. a Terminology can differ. For example, mercapto is sometimes interchanged with sulfanyl in these names. Here, I have chosen to use the most widely adopted name for each of the thiols, which is currently the mercapto version. Technically, however, the correct name (according to the International Union of Pure and Applied Chemistry) is the sulfanyl one, so I have given this in square brackets in a few instances, although this terminology is not yet widely used in the literature (however, that could change over the life span of this book). 7

8 table 4 Chemicals Associated with Smoke Taint in Wine Compound Notes Guaiacol The main smoke-taint compound, with aromas of smoke, phenols, and leather. Detectable in wine at levels of around 25 μg/l, and can reach concentrations of 1,500 μg/l in wine made from grapes that see repeated smoke exposure. Also present in oaked wines at lower levels. 4-Methylguaiacol The second most important smoke-taint compound, with aromas of toast and ash. Detectable in wine at levels of 65 μg/l, and can be present at levels of 300 μg/l in smoke-tainted wines. Also present in oaked wines. 4-Ethylphenol This volatile phenol is one of the main compounds responsible for the sensory impact of Brettanomyces. Has phenolic, horsey, and animal-like aromas. Detectable in wine at levels around 600 μg/l, but present at lower levels in smoke-tainted wines. 4-Ethylguaiacol Also one of the main compounds in Brettanomyces aroma. Described as having smoky, spicy, toasted, and bread aromas. Detectable in wine at levels of around 100 μg/l, and present at around this level in smoke-tainted wines. Eugenol Spicy, clove-like aroma. Has been found at 20 μg/l in smoke-tainted wine, but absent from controls. Present in oak-aged wines. Furfural Sweet butterscotch, caramel, and toast aromas. Has been found at 15 μg/l in smoke-tainted wine, but absent from controls. Present in oak-aged wines. Cresols The p-, m-, and o-cresols are important contributors to smoke taint. These are methylphenols with a distinctive coal-tar smell. 8