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

A general-purpose, automated Fourier-transform infra-red (FTIR) quality-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 through 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 spectrum had been ratioed out. Calibrations were based on relating the peak heights of the absorption bands to the known fat and moisture values of calibration standards prepared by dissolving pure components (peanut oil, canola oil/water) in propanol or by adding to propanol varying amounts of a representative sample pre-analyzed by the Mojonnier method. The time of sample preparation and analysis was 5-7 min per sample, and the predictions obtained by FTIR were within +/-0.30% of values determined by the Mojonnier method. The FTIR portion of the method was automated by programming the instrument by using macro-command language, leaving the operator only to follow menu-driven instructions to carry out the calibration and analysis. As such, the method is rapid and 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 food systems, such as butter, margarine, and chocolate, should be feasible.