95 Development of a rapid method for determining oxidation of soybean oil by near-infrared spectroscopy.

R. L. WEHLING, G. Yildiz, and S. L. Cuppett. Dept. of Food Science and Technology, University of Nebraska, Lincoln, NE 68583-0919.

Near-infrared (NIR) transmittance spectroscopy was used to develop calibrations for quantitative determination of peroxide value (PV), conjugated diene value (CD), and anisidine value (AV) of soybean oils. Partial least squares (PLS) regression and forward stepwise multiple linear regression were used to develop calibrations from log 1/T spectra, as well as from first and second derivatives of log 1/T spectra, for both 1 mm and 2 mm pathlengths. The spectral range from 1100–2200 nm was found to be most useful for PLS regression when using a 2 mm pathlength. When tested with a set of validation samples, PLS calibrations using first derivative spectra gave the best results for PV, while PLS calibrations using second derivative spectra gave the best results for CD and AV. When NIR results were compared with accepted reference methods, linear relationships were obtained for PV (r = 0.994), for CD (r = 0.947), and for AV (r = 0.938). NIR transmission spectroscopy provides a rapid alternative to conventional wet-chemical measurements of oxidation.