Grape must
Grape must is a cloudy, unfermented liquid containing the pulp, skins, seeds and sometimes the stalks of harvested grapes. It is obtained by pressing or crushing, depending on the color of the grape variety. Rich in sugars, it becomes wine through the various stages of vinification.
Composition of grape must
A destemmed grape must is made up of 3-6% pips, 6-9% bloom and 75-85% pulp. It contains 70-80% water and 20-30% organic and mineral components.
Between 1.4 and 2 kg of grapes are needed to obtain 1 liter of must, the main components of which are listed in the following table.
| Component | Quantity | Origin | Storage organ | Oenological role |
|---|---|---|---|---|
| Sugars | 200 - 250 g/l | Produced in the vine's leaves by photosynthesis, then transported by the sap to the grapes | Pulp | 1. Fermentable hexoses (glucose and fructose) = substrates for alcoholic fermentation ⇒ production of ethanol (alcohol). 2. Non-fermentable pentoses (xylose, arabinose, sucrose) ⇒ residual sugars giving mellowness to the wine |
| Organic acids | Tartaric acid: 5 - 7 g/l Malic acid: 2 - 7 g/l Citric acid: 0.1 - 0.3 g/l Ascorbic acid: 50 mg/l Other: 20 - 100 mg/l | Vine | Whole plant | 1.Tartaric acid: main acidity in wine 2. Malic acid: substrate for malolactic fermentation 3. Citric acid: contributes to overall acidity in wine 4. Ascorbic acid: antioxidant product |
| Inorganic acids | Hydrochloric, phosphoric and sulfuric acids: traces | Soil | Whole plant | Stabilization and protection of must against certain diseases |
| Minerals | Potassium: approx. 3 g/l Then phosphorus, calcium, magnesium, iron, copper, zinc, manganese | Soil | Whole plant | Potassium: influences must sweetness and acidity Other: essential yeast products |
| Polyphenols | Variable according to grape variety | Vines | Pigments (anthocyanins and flavonols): pellicle & Tanins: pellicle, seed oil and stalk | Anthocyanins: intensity of red colour Flavonols: intensity of yellow colour Tanins: structure and astringency |
| Nitrogenous matter | Traces | Soil | Whole plant | Ammonia salts: essential for yeasts and bacteria, and therefore for fermentation Amino acids: aromatic precursors Other: stability and preservation |
| Pectins | 0.2 - 7 g/l | Vine | Skin | Gelling actionSmooth, velvety flavors |
| Aromatic compounds and precursors | Traces | Vines | Skins | Wine aromas and taste |
| Vitamins | B, C and E: traces | Vine | Skin and pulp | - |
| Component | Sugars |
| Quantity | 200 - 250 g/l |
| Origin | Produced in the vine's leaves by photosynthesis, then transported by the sap to the grapes |
| Storage organ | Pulp |
| Oenological role | 1. Fermentable hexoses (glucose and fructose) = substrates for alcoholic fermentation ⇒ production of ethanol (alcohol). 2. Non-fermentable pentoses (xylose, arabinose, sucrose) ⇒ residual sugars giving mellowness to the wine |
| Component | Organic acids |
| Quantity | Tartaric acid: 5 - 7 g/l Malic acid: 2 - 7 g/l Citric acid: 0.1 - 0.3 g/l Ascorbic acid: 50 mg/l Other: 20 - 100 mg/l |
| Origin | Vine |
| Storage organ | Whole plant |
| Oenological role | 1.Tartaric acid: main acidity in wine 2. Malic acid: substrate for malolactic fermentation 3. Citric acid: contributes to overall acidity in wine 4. Ascorbic acid: antioxidant product |
| Component | Inorganic acids |
| Quantity | Hydrochloric, phosphoric and sulfuric acids: traces |
| Origin | Soil |
| Storage organ | Whole plant |
| Oenological role | Stabilization and protection of must against certain diseases |
| Component | Minerals |
| Quantity | Potassium: approx. 3 g/l Then phosphorus, calcium, magnesium, iron, copper, zinc, manganese |
| Origin | Soil |
| Storage organ | Whole plant |
| Oenological role | Potassium: influences must sweetness and acidity Other: essential yeast products |
| Component | Polyphenols |
| Quantity | Variable according to grape variety |
| Origin | Vines |
| Storage organ | Pigments (anthocyanins and flavonols): pellicle & Tanins: pellicle, seed oil and stalk |
| Oenological role | Anthocyanins: intensity of red colour Flavonols: intensity of yellow colour Tanins: structure and astringency |
| Component | Nitrogenous matter |
| Quantity | Traces |
| Origin | Soil |
| Storage organ | Whole plant |
| Oenological role | Ammonia salts: essential for yeasts and bacteria, and therefore for fermentation Amino acids: aromatic precursors Other: stability and preservation |
| Component | Pectins |
| Quantity | 0.2 - 7 g/l |
| Origin | Vine |
| Storage organ | Skin |
| Oenological role | Gelling actionSmooth, velvety flavors |
| Component | Aromatic compounds and precursors |
| Quantity | Traces |
| Origin | Vines |
| Storage organ | Skins |
| Oenological role | Wine aromas and taste |
| Component | Vitamins |
| Quantity | B, C and E: traces |
| Origin | Vine |
| Storage organ | Skin and pulp |
| Oenological role | - |
Differences between red and white grape must
- The production process: white grape must is produced by pressing of the harvest, generally without prior crushing or maceration. On the other hand, maceration is necessary for the production of red wines. Red grape must is produced by crushing the harvest to break up the grapes.
- Composition: while the quantity of tannins and pigments increases in red grape varieties, that of sugars, minerals and vitamins is greater in whites.
Aveine's Precision
White or red, must has many uses other than wine-making! It's also used in gastronomy to make balsamic vinegar, distilled beverages such as grappa and brandies, and sometimes even mustard.