Identification of New Odorous Heterocyclic Compounds in French Blue Cheeses

摘要

A number of nitrogen-containing volatile compounds were found in the medium polarity fractions of vacuum distillates obtained from selected French blue cheeses. Six major compounds found in this fraction, some having interesting odors as determined by a GC-sniffing experiment were isolated and characterized by GC with FID and NPD detectors, GC/MS in EI and CI modes, GC/FTIR and ~1H-NMR including two-dimensional NMR. Owing to the spectroscopic data, the six compounds were tentatively identified as a homologous series of 2-alkyl-2,4,5-trimethyl-2,5-dihydro-oxazoles. Syntheses of the six compounds confirmed the tentative results and also allowed or the identification of other minor components of the same chemical family found in this cheese fraction. These syntheses also allowed us to hypothesize a chemical synthesis of these volatiles in cheese from the precursors acetoin, ammonia, and methyl-ketones, which are abundantly present in blue cheeses.