Must weight is a measure of the amount of
sugar in
grape juice (
must) and, hence, indicates the amount of
ethanol that could be produced if it is all fermented to alcohol, rather than left as
residual sugar.
[ Deutsches Weininstitut: Must weights , accessed on March 26, 2009]
Measurement units
In France and many other countries, the grape must density is often recalculated to show
potential alcohol, the percent alcohol content that would be the result if the must were fermented to a completely dry wine.
Refractometer scales
-
Brix (°Bx): Used in Italy, France, and Canada.
-
(KMW): Used in Austria. The scale is divided into Klosterneuburger Zuckergrade (°KMW). However, the KMW measures the exact sugar content of the must.
-
Normalizovaný moštoměr (°NM): Used in the Czech wine, and Slovakia.
Hydrometer scales
Measuring must weight
Must weights are commonly measured in the vineyard to monitor the ripeness of the grapes, which helps select the time of harvest. For this purpose, it is usually measured by using a
refractometer. A few grapes are crushed between the fingers and the must is dripped onto the glass of the refractometer. The refractometer will be calibrated in a must weight scale, but as refractometers actually measure
refractive index (of the grape must in this case), the must weight scale on the refractometer is in effect an indirect measurement, with refractive indices having been pre-converted to their must weight equivalents.
See also
