Flavor constituents of aqueous fraction extracted from Comte cheese by liquid carbon dioxide

Isolation, purification and identification of some low-molecular-weight compounds from a water-soluble extract of Comte cheese was achieved. We used liquid CO2 extraction, subsequent fractionation (by gel permeation and reserve-phase HPLC) and mass spectrometry. Major constituents were N-acyl amino acids (N-acetyl methionine, N-propionyl methionine, N-propionyl leucine, N-propionyl phenylalanine), diketopiperazines cyclo(Pro-Pro), cyclo(Pro-Val), cyclo(Pro-Phe), cyclo(Pro-Leu), cyclo(Pro-Ala)) and non-peptide compounds (theobromine, 4-methyl-t-thiazoleethanol, uracil, (5-6)dihydro-uracil, thymine). These compounds were synthesized and tasted. Most were bitter. N-propionyl methionine had a cheese flavor but was not detected when added to a simulated cheese at 180 mg/L