Term for the unit of measurement used to represent the relative density or specific gravity of grape must. This expresses the mass (weight) in relation to the volume. The mass, also known as extract, consists of the dissolved substances such as fruit pulp particles in the grape must. This is mainly sugar (fructose, glucose), but also acids, minerals, phenolic compounds, proteins and others (some of these substances are then found in the total extract of the wine). The specific gravity of grape must is always greater than 1.0 (water), the difference is largely due to the sugar content. The difference between the "weight of a certain volume of must" and the "weight of the same volume of water" is called the weight ratio. The measurement is carried out by means of areometer (plummet scales), pycnometer and refractometer (light refraction).
Units of measurement
Different units of measurement are used in different countries; the most common are
Klosterneuburger Mostwaage (KMW)
The method was developed by August-Wilhelm Freiherr von Babo (1827-1894) in 1861 at the Klosterneuburger Weinbauinstitut(Lower Austria) on the basis of the saccharometer invented by Carl Joseph Balling (1805-1868). This unit of measurement is mainly used in Austria, Hungary, Italy and some Eastern European countries. The KMW scale is calibrated to a temperature of 20 °C. The exact conversion of KMW to Oechsle = KMW x (4.54 plus 0.022 x KMW); roughly calculated KMW x 5. The conversion formulas of KMW degrees to alcohol content are a rough determination and are only relatively accurate between 16 and 21 KMW:
- 1 KMW = 10 grams or 1% sugar in 1000 grams of must
- 1 KMW corresponds to 4.98 Oe or 0.65 Bé (KMW/1.53)
- (KMW - 4) x 0.85 = % alcohol by volume for white wine
- (KMW - 4) x 0.80 = % alcohol by volume for red wine
Oechsle (Oe)
The method developed by Christian F. Oechsle (1774-1852) in the 1820s and the unit of measurement named after him is mainly used in Germany, Luxembourg and Switzerland. The Oechsle scale is usually calibrated to a temperature of 17.5 °C. One degree Oechsle (Oe) is defined as the increase in weight of 1000 millilitres of must by 1 gram. A litre of must with 50 Oe weighs 1050 grams.
Brix or Brix balling (Bx)
The method developed by Adolf F. Brix (1798-1870) in 1870 and the unit of measurement named after him is mainly used in English-speaking countries. The unit of measurement Balling, also used in...
