Rapid determination of total trans fat content by attenuated total reflection infrared spectroscopy:: An International Collaborative Study

Interest in trans fat labeling has prompted efforts to develop new, more efficient methods for rapidly and accurately determining trans fat content in foods. The lower limit of quantitation, 5% trans fat (as percent of total fat), of transmission infrared official methods, such as AOAC 944.14 and 965.34, for total isolated trans fatty acids is too high to be generally useful for the determination of low levels of trans fats in foods. A novel and rapid (5 min) attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopic procedure was recently developed and applied to food products. This procedure was voted official method AOCS Cd 14d-99. by the American Oil Chemists' Society in 1999 after testing in a 12-laboratory international collaborative study. The results of this study are described in this paper. Analytical ATR-FTIR results exhibited high accuracy in the range investigated, 1-40% trans; results tended to have <2% high bias relative to the gravimetrically determined values. The precision of this internal reflection method was found to he superior to those of transmission infrared official methods. It is recommended that the applicability of the ATR-FTIR method be limited to trans levels of >1% (as percent of total fat).