DIRECT MEASUREMENT OF LIPID-PEROXIDATION IN OIL-IN-WATER EMULSIONS USING MULTIWAVELENGTH DERIVATIVE UV-SPECTROSCOPY

Using second-derivative multiwavelength UV-spectral data (200-300 nm), it was possible to measure lipid peroxidation in oil-in-water lipid e mulsions using a multivariate calibration method (partial least square s regression). For a linoleic acid emulsion (0.42 mM in phosphate buff er, pH 5.5-7.0), with metmyoglobin or ferrylmyoglobin as initiator, co njugated dienes could not be quantified by direct single-wavelength ab sorption spectroscopy (234, 244, or 280 nm) when compared to a referen ce method based on ether extraction and second-derivative spectroscopy at 234 nm. Direct multi-wavelength absorption (200-300 nm) and second -derivative methods (234, 244, 280 nm, and 200-300 nm) provided superi or results with high correlation coefficients (r ranged from 0.78 to 0 .98) when compared to the standard extraction method. The multiwavelen gth second-derivative method (200-300 nm) gave the highest correlation and is recommended for on-line control of lipid peroxidation in heter ogeneous systems.