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

Present-day knowledge regarding total volatile fatty acids of cheese, and particularly in regard to their interrelationship with cheese flavor, is relatively obscure.This lack of knowledge appears to be due, in part, to earlier unsatisfactory quantitative methods for determining these volatile acids.Simple steam-distillation methods on cheese and .otherdairy products are now known to give low and variable results.This has been shown by various investigators (1,4,7,8,9).As a result of their observations on this subject, Hiscox, Harrison, and Wolf (5, 6, 7) developed an involved waterether extraction method using steam distillation which recovered considerably more of the volatile fatty acids from cheese than did the simple steamdistillation method on cheese mush.Their method, however, has never been widely adopted in this country because of the elaborate and time-consuming technique required and the necessity of using special glass-joined stills of empirical dimensions.Recently Smiley, Kosikowsky, and Dahlberg (9) published details of a simplified extraction-distillation method which possessed the advantages of being relatively quick, of not requiring special glass-joined stills, and of recovering fully as much of the volatile acids from cheese as the method of Hiscox, Harrison, and Wolf (7).Their method included the principles of ether extraction of an acid-cheese mixture, removal of volatile fatty acids from the ether by washing with dilute alkali, and acidification of the washings followed by direct distillation in the presence of MgSO4.In the meantime, a specific amount of distilled water was added to the acid-residual material and the mixture directly distilled with MgSO~.The sum of the titrations from these two distillations plus that of the alcohol rinse represented the total volatile fatty acidity of the cheese.In the development of the above method for determining the volatile fatty acids of cheese it was discovered that under certain conditions direct distillation of cheese mush produced results which gave promise of further simplification of the technique.Distillation of cheese mush, as is commonly used in simple steam distillation methods, fails to fully recover the volatile fatty acids of the chees~.Hiscox and Harrison (5) found this retention to be exercised by the fat and Received for publication August 14, 1946.* The authors are indebted to the National Cheese Institute for assistance in financing this study through a research grant to CornelI University, and to Mrs. Jean Beaver and l~rs.Lois Phelps for making some of the analyses.861