A RAPID FTIR QUALITY-CONTROL METHOD FOR DETERMINING FAT AND MOISTURE IN HIGH-FAT PRODUCTS

A general-purpose, automated Fourier-transform infra-red (FTIR) qualit y-control method was developed and evaluated for the rapid analysis of fat and/or moisture in high-fat products, typified by mayonnaise and peanut butter. 1-Propanol was used to solvate fat in peanut butter and fat and moisture in mayonnaise, and the sample was then pumped throug h a 100-mum CaF2 flow cell and the C=O stretching (1748 cm-1) and HOH bending (c. 1650 cm-1) absorptions were measured after the solvent spe ctrum had been ratioed out. Calibrations were based on relating the pe ak heights of the absorption bands to the known fat and moisture value s of calibration standards prepared by dissolving pure components (pea nut oil, canola oil/water) in propanol or by adding to propanol varyin g amounts of a representative sample pre-analyzed by the Mojonnier met hod. The time of sample preparation and analysis was 5-7 min per sampl e, and the predictions obtained by FTIR were within +/-0.30% of values determined by the Mojonnier method. The FTIR portion of the method wa s automated by programming the instrument by using macro-command langu age, leaving the operator only to follow menu-driven instructions to c arry out the calibration and analysis. As such, the method is rapid an d routine and requires no knowledge of FTIR spectroscopy, which makes the procedure suitable for process-quality-control monitoring of high- fat products. Extension of this general approach to other high-fat foo d systems, such as butter, margarine, and chocolate, should be feasibl e.