Generation of Swiss Cheese Flavor Components by the Reaction of Amino Acids with Carbonyl Compounds

Abstract

Previous work has shown that carbonyl-amino acid complexes are important in generating flavors in aqueous extracts of cheeses and Lactobacillus bulgaricus cultures. Glyoxal, methylglyoxal, dihydroxy-acetone, and ethanal were prominant among the carbonyls in such extracts, so the ability of these carbonyls to generate flavors from various amino acids at room temperature was evaluated. Gas chromatography and mass spectrometry of ether extracts of these mixtures were used to identify the particular compounds responsible for the aromas. The amino acids important in the flavor-generating reactions were valine, leucine, isoleucine, methionine, cysteine, phenylalanine, proline, and lysine. Isovaleraldehyde, 2-methylbutanal, isobutanal, phenylacetal-dehyde, and methional, respectively, were formed from leucine, isoleucine, valine, phenylalanine, and methionine via the Strecker degradation. Important flavors in addition to the aldehydes produced by the Strecker degradation were benzaldehyde and acetophenone from phenylalanine, dimethyldisulfide and dimethyltrisulfide from methionine, 2-acetylthiazole from cysteine and methylglyoxal, alkylpyrazines from lysine and dihydroxyacetone, 2-acetyl-1-pyrroline from reaction of certain carbonyls with proline and lysine, 2,5-dimethyl-4-OH-3(2H)-furanone from methylglyoxal, and 2-methylbenzaldehyde from proline and ethanal. Other volatiles identified include isomers of acetyl-methyl-2,3-dihydropyrrolizine from the proline-methylglyoxal and proline-di-hydroxyacetone complexes and δ-valerolactam from the lysine-carbonyl combinations. The reaction products accounted for most of the flavors previously noted in aqueous cheese extracts and cultures of cheese microorganisms.