Brix scale

Degrees Brix measures soluble solids in a liquid, and in fruit juice those solids are mostly sugars. One degree Brix is one gram of soluble solids in 100 grams of solution, so a reading of 12 means roughly 12 percent sugar by weight. Other dissolved materials such as acids and pectins also count, so the number is an approximation of sugar.

The usual tool is a handheld refractometer, which reads how much light bends as it passes through a few drops of juice or syrup. Extension instructions call for a temperature-compensating refractometer, calibrated with a drop of distilled water set to zero, and accuracy can be checked against a sucrose solution of known strength.

Temperature affects the reading. For sugar solutions it shifts by about 0.5 percent sugar for every 10 degrees Fahrenheit, so samples should be at a steady temperature. Bakers and candy makers use Brix to judge fruit ripeness, syrups and fillings.