Studies of Caprylic, Capric, Lauric, and Other Free Fatty Acids in Brandies by Gas Chromatography

Abstract

Concentrations of caprylic, capric, and lauric acids, the most abundant free fatty acids (after acetic) in brandies and wine distillates were determined quantitatively by a gas chromatographic method. The free acids and other materials were removed from the brandy by extracting with methylene chloride. The acids were removed from the methylene chloride layer by extracting with 50% sodium hydroxide, which was then acidified and re-extracted with methylene chloride to recover the acids. The acids were concentrated by evaporation of the solvent. The concentrated acids were converted to n-butyl esters by reaction with boron trifluoride-butanol reagent for 15 minutes at 90°C. The butyl esters were extracted from the reaction mixture using petroleum ether (b.p. 30-60°C). Three microliters of the petroleum ether solution of n-butyl esters with ethyl pelargonate added as an internal standard were injected onto a 6- foot x ⅛-inch FFAP column programmed from 100 to 215°C at 7.5°C per minute. The ethyl esters, along with other neutral compounds, remain in the methylene chloride layer after the alkali extraction of the acids, and can be utilized for quantitative measurement of the ethyl esters. The applicability of the procedure for quantitative measurement of the major free fatty acids and their ethyl esters in an aged brandy was demonstrated.

Typical continuous-still beverage brandies contain 2 to 4 grams caprylic, 2 to 5 grams capric, and 1 to 2 grams lauric acid per 100 liters. Distillates obtained by continuous vacuum distillation or by simple batch distillation contain less. The levels of these fatty acids are reduced when yeast cells are removed from the distilling wine prior to distillation. Some results indicate that the brandy fatty acids and their ethyl esters decrease in concentration during aging in oak cooperage The levels of free fatty acids in brandy are not affected by chillproofing prior to bottling.