A Method for the Estimation of Alcohol in Fortified Wines Using Hydrometer Baumé and Refractometer Brix

Abstract

A novel method for the estimation of alcoholic strength of fortified wines has been developed, linking %v/v alcohol to two simple and rapid enological measurements: refractometer apparent Brix and hydrometer apparent °Baumé. The soluble solid content of fortified wines, measured as true Brix (refractometer) and true °Baumé (hydrometer), can be estimated by the application of experimentally determined correction factors, which compensate for alcoholic obscuration. A calibration plot of true °Baumé versus true Brix, for 35 port wines, having diverse apparent °Baumé and % v/v alcohol, was linear with r² = 0.997. Applying the obscuration formula and rewriting the equation in terms of apparent Baumé and apparent Brix, leads to an expression for alcoholic strength: % Alcohol (v/v) = 1.646 A.Brix − 2.703 A.°Baumé − 1.794. This equation permits the rapid estimation of alcohol content of young fortified wines by two simple measurements: refractometer apparent Brix and hydrometer apparent °Baumé. The method is rapid, economical and extremely portable, and is proposed as a quality-control technique for the three standard fortified wine parameters: % v/v alcohol, hydrometer apparent °Baumé, and refractometer apparent Brix.