Ethanol determination in fermented sugarcane substrates by a diffusive micro-distillation device

The determination of ethanol in fermented substrates is an important parameter for monitoring the production of distilled beverage samples. The correct measurement of its content has a direct impact on the profitability of the process. In this work, a diffusive micro-distillation device (DMDD) is proposed that allows the determination of ethanol directly in the fermented or distilled beverages samples. The DMDD consists of a 5 mL plastic test tube containing a reagent solution of potassium dichromate and sulfuric acid, inserted into another 50 mL polyethylene tube containing the sample. This set is heated in a water bath for 15 min at 80 °C, providing the ethanol diffusion, which reacts with the receptor solution contained in the test tube. The chromium (III) produced by the oxidation reaction, is spectrophotometrically quantified at 589 nm. The proposed procedure has a linear range between 1 and 12% (v/v) with R² = 0.999 and RSD = 3.8% and results in agreement with those obtained by the distillation-densitometry official method.