Must weight

Must weight describes the density of grape must, so the mass of the must in proportion to its volume. It is an indicator for the expected alcohol content of wine in complete fermentation of the sugar dar. Therefore, the must weight is also commonly referred to as gradation or alcoholic potency.

Must weight is thus a measure of the proportion of all solutes in grape must. These are also referred to as an extract. Is composed mainly of this extract of sugar (dextrose and fructose ), acids, glycerol and in small quantities from phenols, pectins, proteins, and minerals. Due to the high sugar content, the density must be always higher than that of water, that is greater than one kilogram per liter.

The density of the must can be determined by various physical methods. These include:

• The buoyancy of a hydrometer ( hydrometer ) or a hydrostatic balance ( hydrometer )
• The balance of mass based on the volume of the pycnometer
• Measurement of the refraction of light by means of a refractometer
• Measurement of the optical rotation of the sugar with a saccharimeter

In addition to the different measuring methods also different measurement scales and hence different units are used in different countries. So the must weight in Germany, Luxembourg and Switzerland is measured in degrees Oechsle. In Italy, Austria, Hungary, Slovakia and the countries of former Yugoslavia is in KMW, or measured degrees Babo. Degrees Baume be used in France and Spain. Brix, or the almost identical unit Balling, are mainly used in English speaking countries.

These units can be converted into each only about rather complicated formulas, since their ratios to each other are not linear. For this reason, tables are usually used, from which the values ​​can be sufficiently accurately read.

As a rule of thumb one can say that 10 grams of sugar per 1000 grams must, by fermentation 0.66 % vol. Alcohol yield.

Must weight is an important factor for determining the read timing. In Germany, Austria and Switzerland, the must weight over the wine law forms the basis for the classification of wines of quality. For each of these classes is a so-called minimum must weight that has to be crossed, provided.

Especially in warm wine regions the must weight is but alone mean very little. Only based on the must weight would be simple French country wines in Germany already read. Italian Amarone Valpolicella from would already be a Beerenauslese. Therefore, in warm wine regions also the acid, the pH and the physiological maturity for classification into quality classes are used.