Determination of free fatty acids in foods by flow injection

A flow injection manifold has been developed for the spectrophotometric determination of free fatty acids (FFA) at 716 nm after continuous extraction into an organic phase of soaps formed by the reaction of copper acetate with the analytes. The carrier system stream was toluene and the reagent stream aqueous copper acetate‐pyridine (50 g litre−1). The calibration graph was linear over the range 1 × 10−4 to 5 × 10−3 M oleic acid using an injection volume of 115 μl. The injection rate was 75 samples h−1 with a precision of 109% (RSD). Though this procedure does not permit the total recovery of short‐chain fatty acids it is very effective in reflecting the total concentration of FFA. The system has been applied to the determination of total FFA in olive oil, milk fat and cocoa butter. Although the values obtained by the proposed method are lower than those obtained by the reference method (titration) and by chromatography, their comparison shows good linearity.