Identification of aroma compounds in Parmigiano-Reggiano cheese by gas chromatography/olfactometry

The volatile compounds in Parmigiano-Reggiano cheese were isolated by solvent extraction/high vacuum distillation, followed by separation into acidic, basic, water-soluble, and neutral fractions. The neutral fraction was further fractionated by a normal-phase liquid chromatography. Aroma compounds were identified using gas chromatography/Osme-mass spectrometry and confirmed with retention index of standards. Butanoic, hexanoic, octanoic, and decanoic acids are the major free fatty acids contributing to cheesy, lipolyzed aroma. Ethyl butanoate, ethyl hexanoate, ethyl octanoate, ethyl propanoate, ethyl pentanoate, ethyl heptanoate, and ethyl decanoate are the major esters contributing to fruity aroma. 2-Methylbutanal, 3-methylbutanal, 2,4-hexadienal, 2-butenal, pentanal, hexanal, heptanal, diacetyl, phenylacetaldehyde, dimethyltrisulfide, and methional were identified to be odor-active. It was found that 2,3-dimethylpyrazine, 2,6-dimethyl-pyrazine, 2,5-dimethyl-3-ethylpyrazine, trimethyl-pyrazine, 5-ethyl-2-methylpyridine, 2,3-dimethyl-5-ethylpyrazine, 2,3,5-trimethyl-6-ethyl-pyrazine, furfural, and 2-furanmethanol contribute to the nutty, roasted aroma in this cheese.