Interrelationships between pH, Populations of Propionibacterium Shermanii, Levels of Free Fatty Acids, and the Flavor Ratings of Swiss Cheeses

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Abstract
Fifteen experimental cheeses were examined priodically during 1 year. The following variations in the normal cheeses were found: pH off the press (experimentally induced variation), 4.95-5.37; maximum numbers of Propionibacterium shermanii. 145 million/g to 2,100 million/g; maximum levels of acids[long dash]acetic, 38-59; propionic, 44-104; butyric, 6-40; higher, 22-48 uM/g. With added sodium propionate, pH and numbers of P. shermanii increased but production of propionic acid decreased. Five commercial cheeses, examined for flavor and fatty acid levels, typically had higher levels of acetic acid than the experimental cheeses. Significant relationships were found between pH off the press and growth of P. shermanii and also between the maximum levels of propionic acid and both the maximum numbers of P. shermanii and the P. shermanii numbers-time integrals. All relationships involving the "sweet" flavor component are without significance. With one exception, all relationships involving the "nutty" flavor component are either of doubtful or of no significance. The relationship between nutty flavor and propionic acid levels may be significant. Propionic acid is a component of the flavor complex, but other compounds appear to be responsible for both the nutty and the sweet characteristics of typical Swiss cheese flavor.