Development of a Headspace Gas Chromatographic--Mass Spectrometric Method for Determining Methyl-Ketones and Secondary Alcohols in Blue Cheese

The aim of this work is to develop a rapid and direct gas chromatographic (GC) method for the analysis of methyl-ketones and secondary alcohols in blue cheese using headspace with constant heating temperature coupled to GC with a mass spectrometric detector. Repeatibility of the method is assessed; the coefficient of variation for individual methyl-ketones ranges from 4.5 to 9.6%, and the total mean value for methyl-ketones is 466.1 ± 5.1 µg/100 g with a coefficient of variation of 1.1%. The coefficient of variation found for individual secondary alcohols in this study ranges from 11.2 for 2-pentanol to 22.6 for 2-nonanol. The total mean concentration for secondary alcohols (2-propanol, 2-pentanol, 2-heptanol, and 2-nonanol) is 80.5 ± 5.0 µg/100 g with a coefficient of variation of 6.2% (2-pentanol and 2-propanol representing 62% of the total secondary alcohols studied). Recovery ranges between 80.3 to 88.6% for individual methyl-ketones and between 81.3 and 85.4% for secondary alcohols.