Csw Wine Chemistry And Science-Y Stuff

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Ethyl alcohol

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Main alcohol found in wine

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Glycerol

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Secondary alcohol found in wine

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Methyl alcohol/Methanol

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Secondary alcohol found in wine

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Fusel alcohols/fusel oils/higher alcohols

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Secondary alcohol found in wine

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Tartaric acid

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Most prevalent acid in both grapes and wine. Forms solid crystals at low temperatures. Naturally in grapes, not caused by fermentation

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Malic acid

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Green apple acid. The riper the grape, the lower the malic acid. Not caused by fermentation

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Lactic Acid

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Softer, smoother, rounder, creamier acid. Not found in grapes but malic acid can be converted into lactic acid in wine by lactic acid bacteria

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Acetic acid

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Vinegar acid. Higher concentrations can be a fault, lower concentrations in reds can be desirable. Low level typically created during fermentation

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Acetobacter

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Bacteria that causes a chemical reaction between ethanol and oxygen that increases acetic acid and creates a wine fault

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Succinic Acid

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Minor component in grapes and natural product of normal alcoholic fermentation

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TA

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Total Acidity - the volume of all acids in a wine

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pH

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Combined chemical strength of the acids present. Normal wine is 2.9-3.9 pH. The pH is better indication of wine stability than TA and helps determine sulfur additions

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Glucose and Fructose

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The sugars in grapes. Usually roughly equal

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How much sugar do grapes usually contain at harvest?

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15-28%

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Anthocyanins

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Phenolic compound that gives red wine its color

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Flavonols

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Phenolic compound giving white wines their yellow color. They increase in grapes with increased exposure to sunlight

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Tannins

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Phenolic compound and natural preservative that helps protect red wines from oxidation during aging. Textural drying sensation

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Vanillin

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Phenolic compound in both vanilla beans and oak barrels

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Reservatrol

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Phenolic compound in wine believed to give wine health benefits

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Phenolic compounds/phenolics/polyphenolics/polyphenols

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Molecules in many wines. Largely present in skins and seeds of grapes, so there are more of these in red than white wines

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Aldehydes

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Oxidized alcohols formed when wine is exposed to air.

Most common: acetaldehyde, which is formed by the oxidation of ethanol and is what makes fino Sherry so distinctive

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Esters

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Formed by the joining of an acid and an alcohol. Largest group of odiferous components in wine

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Ethyl Acetate

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Common ester resulting from acetic acid and ethanol. At low levels gives wine a fruity floral aroma, at higher levels it smells like nail polish remover or wood glue

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What does TCA stand for?

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2,4,6-Trichloroanisole

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TCA/2,4,6-Trichloroanisole

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Chemical in corked wines caused by a mold that can grow on/in bark of the cork oak tree, on winemaking implements, or in winery itself. Highly persistent. Not harmful but mutes fruit flavors and causes basement odor in wine

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Sulfur dioxide (SO²)

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High concentration of SO2 is a wine fault - burnt matches smell, sometimes burning sensation in throat and nose. *The more acidic the wine, the more noticable the SO2.*

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Hydrogen sulfide (H²S)

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Happens when sulfur rich wine sits too long without oxygen. Rotten eggs odor.

Most often caused by barrel or tank resting too long with lots of yeast sediment. Can also be an issue with screwcap wines.

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Mercaptan

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Sulfur + ethanol = ethyl mercaptan. Smell of garlic or onions. In real life it's added to odorless natural gas to help people smell leaks. Less fixable than other two sulfur wine faults.

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The only two major bacteria that can survive in wine

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1. Lactic bacteria (causes malolactic fermentation)

2. Acetobacter (converts alcohol into acetic acid)

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Acetic acid as a wine fault

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Odor of vinegar

Caused by bacteria (acetobacter)

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Butyric acid

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Wine fault smell of rancid butter or spoiled cheese

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Lactic acid as a wine fault

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Smell of sauerkraut or goat

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Ethyl acetate as a wine fault

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Smell of nail polish remover or model airplane glue.

Caused by ethanol + acetic acid

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Ascensence

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When acetic acid and ethyl acetate combine

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Geranium

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Wine fault caused by bacteria.

Smells like crushed geranium leaves.

Normally caused by incomplete malolactic fermentation or the improper breakdown of the preservative service acid

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Brettanomyces

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Aka brett

Member of the yeast family. Controversial wine fault - some like it in small quantities, others not at all

Smells include sweatiness, horse-y smells, Band-Aids, can deaden other flavors in a wine

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Green as a wine fault

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Odor of leaves

Usually from using underripe grapes

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Oxidized

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When oxygen dissolves into wine and creates acetaldehyde

Can brown wines and deaden fruit character.

Nutty, carmelized character

Sometimes intentional (i.e. fino Sherry)

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Maderized

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Wine fault resulting in cooked or baked odor

Caused by excessive heat or oxidation

Sometimes desirable (i.e. Madeira)

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Moldy as a wine fault

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Moldy smell.

Caused by using moldy grapes or barrels

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Rubbery as a wine fault

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Smell of rubber

Associated with low-acid wines or too much sulfur

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Stagnant

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Wine fault giving smell of stale water

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Stemmy

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Wine fault giving bitter green odor of grape stems

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Wet cardboard

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Wine fault causing papery chemical odor

Either cork taint (TCA) or misuse of filtering pads + materials at winery

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Yeasty/leesy

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Wine fault for wines that aren't sparkling wines aged on lees (i.e. Champagne)

Pronounced odor of yeast

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Reductive

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Not an accurate wine fault term! Broad catch all to refer to faults from winemaking conditions without oxygen.

Smells of rotten eggs, garlic, matches, cabbage, or burnt rubber