Brix measures soluble solids as degrees on a refractometer, and in fruit it mostly reflects sugars, so it is used as a proxy for ripeness and sweetness. In honey the same instrument is used the other way round, to infer moisture content. A Brix figure is only comparable when the sample preparation and temperature of measurement are stated.
Why preparation changes the number
Whole thawed fruit, drained fruit and homogenised pulp give different readings from the same lot, because the juice that drains carries a different solids concentration from the flesh. Temperature matters too: refractometers are calibrated at a reference temperature, usually 20 degrees Celsius, and readings need correcting away from it.
Specifying it usefully
State the minimum, the preparation, the instrument type and the temperature. Set the minimum from your application rather than from ambition – Brix in berries swings with variety, season and region, and a narrow window turns into a supply problem rather than a quality gain.
More on how the compositional, defect and safety families fit together: frozen berry specifications.
