Infrared Spectroscopic Determination of Total Trans Fatty Acids

This unit describes the attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopic method (AOCS, 1999a AOAC International, 2000), a novel method for measuring the total amount of fat with isolated trans double bonds. It is applicable to natural fats (ruminant fats) and processed fats and oils (partially hydrogenated fats and oils or refined vegetable oils) consisting of long-chain fatty acid methyl esters or triacylglycerols with trans levels 5%, as percent of total fat (AOAC International, 2000). 

The fatty acid composition of the trans-free reference fat plays a critical role. If the selected trans-free fat is significantly different from the matrix of the fat investigated, it may have an adverse impact on accuracy, particularly near the official method s lowest trans level of quantitation, 5% (AOAC International, 2000) or 1% (AOCS, 1999a). This trans-free reference fat must be carefully selected and should represent as much as possible t e composition of the unknown trans fat or oil being determined. 

Heated attenuated total reflection (ATR) infrared cell (see Critical Parameters) FTIR spectrometer (see Critical Parameters) 

Low-lint tissue paper Boiling water bath 

Prepare neat (solvent-free) trans calibration standards by weighing accurately, on an analytical balance (to the nearest 0.0001 g), 0.3 -x g of a trans-free reference fat and x g of trielaidin (TE) into each of a series of 10-mL beakers, where x equals 0.0015, 0.0030, 0.0150, 0.0300, 0.0600, 0.0900, 0.1200, and 0.1500 g. Store calibration standards in plastic screw-cap vials. 

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D1.7 Infrared Spectroscopic Determination of Total Trans Fatty Acids... 

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