Evolution of Volatile Compounds in Ripening Raw and Pasteurized Milk Cheddar Cheese Observed by Gas Chromatography

Gas chromatographic techniques were applied to the study of the volatile compounds in raw and pasteurized milk Cheddar cheese during the ripening process.The major volatile compounds in both types of Cheddar cheese are acetic acid, butyric acid, ethanol, methyl ethyl ketone, and secondary butyl alcohol.Acetyhnethytcarbinol and diacetyl are also present, generally at trace levels.Acetic acid, acetylmethylcarbinol, ethanol, and diacetyl are detectable on the first day of ripening.The concentration of acetic acid and ethanol increased throughout ripening.Acetyhnethylcarbino] decreased from its original level.Butyric acid, secondary butyl alcohol, and methyl ethyl ketone appeared later in the ripening period.This was generally true for both the raw and pasteurized milk cheese; however, the rate of change of these compounds was much faster in the raw milk cheese.Also, the compounds in the raw milk cheese increased to much higher levels than those in the pasteurized milk cheese.It is hypothesized that methyl ethyl ketone and secondary butyl alcohol arise from the dehydration of 2,3-butylene glycol which comes from acetyhnethylcarbinol.