Must weight

The must weight describes the density of grape must , i.e. the mass of the must in relation to its volume . It is an indicator for the expected alcohol content of wine after complete fermentation of sugar . Therefore, the must weight is colloquially often called gradation or alcoholic potency called.

The must weight is a measure of the proportion of all dissolved substances in grape must, which are collectively referred to as extract . It consists mainly of sugar ( grape sugar and fructose ), acids and glycerin and, in small amounts, phenols , pectins , proteins and minerals . Due to the high sugar content, the density of must is always higher than that of water, i.e. greater than one kilogram per liter.

Measurement principles

Measurement of the must weight with the refractometer

The must weight can be determined using various physical methods :

the buoyancy of a lowering spindle ( hydrometer ) or a hydrostatic balance (lowering balance)
weighing the mass in relation to the volume with the pycnometer
Measurement of the refraction of light using a refractometer
Measurement of the optical rotation of the sugar with a saccharimeter .

units

In addition to the different measuring methods, different measuring scales and thus different units are used in different countries to determine the must weight:

in Germany , Luxembourg and Switzerland it is measured in degrees Oechsle .
in Italy , Austria , Hungary , Slovakia and the states of the former Yugoslavia , measurements are made in KMW ( Klosterneuburger Mostwaage ) or Grad Babo .
in France and Spain are degrees Baume used.
In the English-speaking countries, degrees Brix or the almost identical unit Balling are mainly used.
in the Czech Republic and also in parts of Slovakia it is measured in normalizovaný muštomer .

These units can only be converted into one another using very complicated formulas, as their relationships to one another are not linear . For this reason, tables are usually used from which the values can be read with sufficient accuracy.

As a rule of thumb , it can be said that 10 grams of sugar per 1000 grams of must (i.e. 1 percent by mass of sugar) yields 0.66 percent alcohol by volume through fermentation .

meaning

The must weight is an important factor in determining the time of harvest . In Germany, Austria and Switzerland, the must weight forms the basis for dividing wines into quality classes via the wine law : a minimum must weight is required for each class , which must be exceeded.

However , the must weight alone is not very meaningful, especially in warm wine-growing regions . So - based solely on the must weight - simple French country wines in Germany would be Auslese and Italian Amarone della Valpolicella from Valpolicella would already be Beerenauslese . Therefore, in warm wine-growing regions, the acidity , the pH value and the physiological maturity are also used to classify the quality classes.

Individual evidence

↑ Since the exclusion of Grad Baumé units in France by Decree No. 61–501 of May 1961 on units of measurement and the control of measuring devices, the French regulation refers to the sugar content, expressed in grams per liter.

literature

Hans Ambrosi : Wine from A to Z . 2nd edition Gondrom Verlag, Bindlach 2003, ISBN 3-8112-2105-1 .
Horst Dippel (greeting), Florian Lange (editing): Das Weinlexikon . Fischer Verlag, Frankfurt / M. 2003, ISBN 3-596-15867-2 .
Jens Priewe : Wine. The big new school . 2nd ed. Verlag Zabert Sandmann, Munich 2006, ISBN 3-89883-137-X .
Eckhard Supp (Ed.): The Brockhaus - Wine . FA Brockhaus, Mannheim 2005, ISBN 3-7653-0281-3 .
Norbert Tischelmayer: Wine Glossary. 2777 terms related to wine . Np Buchverlag, St. Pölten 2001, ISBN 3-85326-177-9 .

[1] Since the exclusion of Grad Baumé units in France by Decree No. 61–501 of May 1961 on units of measurement and the control of measuring devices, the French regulation refers to the sugar content, expressed in grams per liter.