Evolution of Acetaldehyde, Methanol, and Furfural in Pisco Distillation

Acetaldehyde, methanol, and furfural are potentially toxic compounds that can be found in fruit-distilled spirits, such as pisco. It is important to determine their behavior during distillation to separate them and minimize their content in the product because its content in pisco is limited according to the Pisco DO Regulation to methanol, 60; acetaldehyde, 100, and furfural, 5 mg/100 cc of anhydrous alcohol. For this purpose, pisco was produced using the traditional method (natural fermentation and batch distillation in a copper alembic). During distillation, 17 distillate fractions (Fn) were received with volumes: F1 and F2:50 mL, F3 to F13:200 mL, and F14 to F17:100 mL. In each fraction, the alcohol concentration was determined by densimetry and that of acetaldehyde, methanol, and furfural by gas chromatography. Acetaldehyde is found in all fractions of the distillate (66–9°G.L.). In a higher proportion in the first fractions, corresponding to a range between 66 and 57°G.L., it can be called a "head" compound. Methanol flows from the first distillate fractions to the last ones and is in an almost constant concentration in the intermediate fractions, being considered, in this case, a "heart" compound. Furfural appears in the last fractions, which correspond to an alcoholic strength range between 25 and 9°G.L. and could be considered a "tail" compound. The content of these compounds in the distillate will depend on the "head" and "tail" cuts. The removal of methanol is difficult because it is found in a higher proportion in the "heart" fraction that would be the final product.