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A Rapid Direct-Distillation Method for Determining the Volatile Fatty Acids of Cheese^*

Department of Dairy Industry, Cornell University, Ithaca, New York

ABSTRACT

A very short and rapid method for the determination of volatile fatty acids in cheese is presented. This new method required that a finely ground sulphuric acid-cheese mixture with a low pH be refluxed to drive off CO₂ and directly distilled in the presence of MgSO₄. A specific quantity of water (250 ml.) was added prior to distillation and the amount of distillate recovered was limited to 285 ml. The insoluble volatile fatty acids were washed from the condenser tube by neutral alcohol. Distillates were titrated with N/20 NaOH, using phenolphthalein as indicator. The sum of the titrations of the water distillate and the alcohol rinse represented the total volatile acidity of cheese.

The advantages of this method are that high recovery of the volatile fatty acids from cheese is accomplished in a very short time without the use of special glass-joined stills and with a minimum of apparatus and chemical reagents. This method is very adaptable to circumstances where large numbers of cheeses need to be tested in a short time.

Direct distillation in the presence of MgSO₄ brought about a very effective recovery of pure lower-chain fatty acids when fresh fat and casein were in the mixture. Under these conditions, recovery was indirectly related to the number of carbon atoms present in each fatty acid.

^* The authors are indebted to the National Cheese Institute for assistance in financing this study through a research grant to Cornell University, and to Mrs. Jean Beaver and Mrs. Lois Phelps for making some of the analyses.