Determination of free fatty acids in beer by multilevel solvent extraction-gas chromatography

Free fatty acids(FFAs) with off flavor are one kind of the most important compounds which affects the beer flavor greatly.The contents of free fatty acids in beer were extremely low and unstable.FFAs were determined by solvent extraction and gas chromatography(GC) in this paper.Beer samples were extracted for 3 times(by organic solvent extraction,the reversed phase extraction with alkaline solvent,and organic solvent extraction).Methanol/sulfuric-acid was added into the samples,at last they were concentrated into GC analysis.There was good duplication and high recovery by this method.The average recoveies of caprylic acid,capric acid and lauric acid were 86.26%,92.19% and 83.57%,respectively. The linear ranges of caprylic acid,capric acid,lauric acid and palmitic acid were 2.326～326 mg/L,0.362～62 mg/L,250 ～50mg/L and 330～30 mg/L,respectively,with correlation coefficients of 0.9996～0.9999.