Determination of the free fatty acids responsible for goaty flavor using multilevel solvent extraction-gas chromatography

Objective:A method for the simultaneous determination of the free fatty acids (FFA) in goat milk such as caproic acid, caprylic acid and decanoic acid, which were responsible for goaty flavor, was developed by multilevel solvent extraction-gas chromatography. Methods:Extractions were carried out with chloroform/methanol (2∶1, v/v) and sodium carbonate solution. The fatty acid methyl esters (FAMEs) which were obtained by the esterification of the FFA with boron trifluoride-methanol solution was qualified and quantified by gas chromatography equipped with flame ionization detector. Results:Over the concentration in the range of 5.11¹63.52mg/L for caproic acid, 5.05¹61.73mg/L for caprylic acid and 7.54²41.38mg/L for decanoic acid, the coefficients of the calibration curves were above 0.998. The limits of detection (LOD) were 0.16mg/L for caproic acid, 0.19mg/L for caprylic acid and 0.25mg/L for decanoic acid. The limits of quantification (LOQ) were0.54mg/L for caproic acid, 0.63mg/L for caprylic acid and 0.83mg/L for decanoic acid. The average recoveries of the three kinds of FFA ranged from 88.5% to 103.4% with relative standard deviations (RSDs) between1.98% and 6.09%. Conclusion:The method was economical, accurate, and sensitive, which may be used for determination of the FFAs in milk.