What (Red) Wine is Made Of

Red wine is comprised mostly of water, and then:

Soluble Solids:

Polysaccharides, especially pectins.

Sugars - glucose and fructose. The drier the wine, the less sugars. Most red wines are completely dry (less than 0.1% reducing sugars - mostly nonfermentable sugars like pentoses).

Acids:

Tartaric, citric, malic, lactic (malic and lactic are often in inverse proportions, due to malo-lactic fermentation) sulfuric and acetic. Too much of any of these (especially sulfuric or acetic acids) will ruin the wine. Maximum legal permitted volatile acidity on the average is about 0.120 grams per 100 mL of wine. Few wines reach anywhere near this high.

Alcohols:

Chiefly ethanol.

Methanol is found in trace quantities in grapes and is mostly found in fruit (not grape) wines due to pectinase activity.

Sorbitol and Mannitol are rare in grape wines.

Alcohol level is listed on the wine label.

Carbonyl Compounds:

Wine is full of aldehydes and ketones. Acetaldehyde and diacetyl are the most common.

Esters:

Chiefly Ethyl Acetate at levels of 40 mg/L average.

Also a trace amount of a wide variety of Esters are responsible for the aroma of wine.

Nitrogen Compounds:

Nitrogen, amino acids (chiefly proline) and ammonia, in tiny quantities (60 mg/L).

Phenolic Compounds:

Responsible for much of the flavor and body of wine, these are a major component of wine.

Benzaldehyde (vanillin) and Benzoic acid (Vanillic and Gallic acids) are the phenolic compounds one tastes the most in wines.

Catechins may make up the largest quantity of Phenols.

Anthocyanins are responsible for the pigmentation of red wine, and are present in proportion to the color of the wine.

Resveratrol (attributed with reducing cholesterol) is a phenolic compound.

Ash:

On the average about 2.5 g/L of ash are found in wine.

Ash being defined as the inorganic matter that remains after evaporation and incineration.

Cations - most of the ash falls into this class and includes potassium, sodium, calcium, magnesium, iron, copper, lead, arsenic, etc.

Trace minerals include pretty much anything that can be found in the soil, e.g. Aluminum, Barium, Cadminium, etc.

Chemical Additives

SO2 is the most commonly considered additive. The legal limit for maximum SO2 in the US is 350 mg/L - it is lower in most other countries. It is the Free SO2 that a tiny percent of the population is bothered by. While the US does not set limits for Free vs. Total SO2, some other countries do, and since US and other wines are imported to those countries, the practical limit for Free SO2 is 3 mg/L (the lowest limit). Levels of SO2 above .5 mg/L are noticeable in the smell of wine to most people, and is considered undesirable.