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H. YANG, Department of Agricultural & Biological Engineering, The Pennsylvania State University, 227 Agricultural Engineering Building, University Park, PA 16802 and J. Irudayaraj.

Fourier transform infrared (FTIR) spectroscopy has been used to quantify and qualify edible oils and fats. Transmission cell and attenuated total reflectance (ATR) are two of the most common accessories for such oil and fat analysis. Both techniques require some sample preparation. Photoacoustic spectroscopy (PAS) can be used with FTIR to perform nondestructive analysis of fats and oils.

The objectives were to characterize lard, soybean oil, and butter by the FTIR-PAS technique and valid FTIR-PAS measurement using FTIR-ATR results.

The samples were lard, soybean oil, and butter. The FTIR spectroscopy with a photoacoustic detector and a ATR sampling accessory were used to perform PAS and ATR measurements, respectively.

The PAS technique is simple and requires no sample preparation, unlike ATR. Optimal PAS instrumental parameters for obtaining quality spectra were a scanning speed of 5 kHz, number of scans of 256 scans/sample, and a resolution of 4 cm-1. Results for soybean oil compare well with those available in the literature. The ATR spectra of butter were better than those of its PAS counterpart. Functional groups corresponding to vibration mode and intensity are provided for soybean oil and lard.