SAMPLE PREPARATION BEFORE CAPILLARY GAS-CHROMATOGRAPHIC ESTIMATION OFFREE FATTY-ACIDS IN FERMENTED DAIRY-PRODUCTS

A method is described for pretreatment and clean-up of samples for use in estimating free fatty acids (FFAs) in fermented products. Large co ncentrations (7-15 g/L) of lactic acid in fermented dairy products can interfere with estimation of FFAs. Lipids and FFAs were extracted wit h a mixture of diethyl ether and heptane (in equal volumes); about 3% of the lactic acid in the sample was also extracted. The FFAs were iso lated by solid-phase extraction with a column containing 1000 mg of an aminopropyl bonded silica sorbent. Lactic acid was also adsorbed by t he column but the method was not intended for estimation of content of lactic acid in fermented dairy products. The accuracy and the repeata bility of the method were established by studies on recovery of FFAs a dded to yoghurt and replicate analysis of yoghurt samples; recoveries were 0.70-1.0 and relative standard deviation was about 3%.