Determination of total fat and saturated fat in foods by packed column gas-liquid chromatography after acid hydrolysis

The new definition of total fat in FDA regulations implementing the Nutrition Labeling and Education Act of 1990 necessitates the quantitation of all lipid fatty acids and the summation of their triglyceride equivalents. A gas-liquid Chromatographic (GLC) method using a packed column has been developed for quantitative measurement of total fat and saturated fat in foods. Fatty acids are released from food matrices by acid hydrolysis, and then extracted, esterified to their methyl esters and determined by GLC. Total fat and saturated fat are calculated in accordance with the new definitions of these components. Fat content determined by the acid hydrolysis-GLC methodology was compared with fat content determined by a direct AOAC gravimetric method for 23 food products containing between about 1 and 75% fat by weight. For all food products studied, the relationship between the results obtained by the two methods was best described by a straight line that had a correlation coefficient of 0.94. Results of repeated extractions and analysis of a milk-based infant formula (SRM 1846) suggest that this material may be useful as a quality control standard.