A rapid method for the quantitative determination of short-chain free volatile fatty acids from cheese

The determination of free volatile fatty acids (FVFA) is of interest in the analysis of cheeses. As these compounds are components of taste and flavor , they give indications on metabolic reactions taking place during cheese r ipening and can provide an evaluation of cheese defects and their causes. O ne of the most widely used methods for the determination of FVFA in cheese involves preliminary recovery from the matrix by steam distillation, follow ed by gas chromatography separation. Relatively high distillate volumes mus t be collected to achieve a quantitative yield of all the compounds of inte rest, so that, as a result, the solution is too diluted to achieve good ins trumental sensitivity. In this paper, an alternative method for the determi nation of C2-C6 free carboxylic acids in cheeses involving the use of a Nuk ol capillary column and crotonic acid as internal standard is described. Th is method is quick and cheap, as the sample preparation is a simple extract ion with water. The underivatized FVFA are then directly separated by gas c hromatography. Using this method, all FVFA in cheeses can be quantified wit h good repeatability and excellent recovery.