A Simplified Extraction-Distillation Method for the Determination of the Volatile Fatty Acids of Cheese*

Summary A method for determining the volatile fatty acids of cheese is described. The method, referred to as the simplified extraction-distillation method, is based on two distillations of acid cheese solution, one associated with the fat phase and the other with the residual material. After ether extraction of the acid-cheese mixture, the volatile fatty acids were removed from the ether with dilute alkali. The alkali rinses were heated to drive off the ether, then acidified, refluxed to remove carbon dioxide, and distilled in the presence of MgSO 4 until crystallization occurred. In the meantime, 250ml. of distilled water were added to the residual material and the solution distilled until 280ml. of distillate were collected. The sum of the titrations from the two distillations plus that of the alcohol rinse represented the total volatile acids of the cheese. This new method and the method of Hiscox, Harrison, and Wolf (5) gave nearly identical results for a wide variety of cheeses. It has advantages over the latter method in that no special apparatus is necessary, more distillations can be accomplished in the course of a day, and the time required to analyze a sample of cheese is very greatly reduced. The findings of Friedemann (2) that acetic, butyric, caproic, and caprylic acids can be quantitatively recovered by distilling in the presence of MgSO 4 were confirmed. In addition, capric and lauric acids were quantitatively recovered under similar conditions, while myristic acid was incompletely recovered. Nonvolatile fatty acids, such as palmitic and oleic, exerted a retentive effect on caprylic, capric, lauric, and myristic acids during direct distillation in the presence of MgSO 4 with the degree of retention being in direct relationship to the number of carbon atoms present in the volatile acids. When butyric and caproic acids were distilled, the nonvolatile acids exerted no retentive effect.