Determination of fat content and fatty acid composition through 1-min transesterification in the food sample principles

Base-catalysed transesterification can occur in water-containing foods, such as ice-cream or milk, because it happens much faster than saponification. Under the conditions proposed, it takes 1 min at ambient temperature. The reaction must be stopped before relevant saponification occurs, reducing the pH. The method enables the determination of the fat content through the sum of all fatty acids as well as the fatty acid composition without previous extraction from the foodstuff. Some foods, such as meat or cheese, are heated for a short while in dimethylformamide (DMF) in order to solubilize the fat in the reaction medium. A system of four internal standards verifies the completeness of the transesterification for every analysis and checks for relevant saponification or discrimination by GC analysis.