Flavor chemistry of popcorn

Graduation date: 1969Popcorn was popped conventionally in oil and in a microwave\ud oven without oil. Volatile components were collected by condensation\ud of popper headspace gases and by vacuum steam distillation of\ud a slurry of ground, popped corn in distilled water. The organic\ud compounds were extracted from the aqueous condensate and vacuum\ud distillate with diethyl ether. The concentrated ether extracts were\ud analyzed by a coupled gas chromatograph-mass spectrometer utilizing\ud three different procedures. These were: (1) a 300 foot by 0.01\ud inch ID capillary column, into which samples were injected with a\ud 50:1 inlet split, with the effluent end connected directly to the ion\ud source of the mass spectrometer; (2) the same directly coupled\ud capillary column but with samples previously trapped from a packed\ud column introduced without splitting; (3) mass spectrometric analysis\ud of a portion (5 to 10%) of the effluent stream from a 12 foot by 1/8\ud inch OD packed column.\ud Thirty-six compounds were positively identified by comparison of their spectra with reference spectra. Relative retention time\ud coincidence with known compounds confirmed the mass spectral\ud identifications. Those compounds positively identified include pyrazine,\ud 2, 5-dimethyl pyrazine, 2, 3-dimethyl pyrazine, 2-ethyl-5-\ud methyl pyrazine, 2-ethyl-3, 6-dimethyl pyrazine, 2-pentyl furan,\ud furfural, 2-acetyl furan, 5-methyl furfural, furfuryl alcohol, 5-hydroxymethyl\ud furfural, acetaldehyde, 2-methyl propanal, 5-methyl\ud butanal, pentanal, hexanal, benzaldehyde, phenylacetaldehyde,\ud diacetyl, ethyl acetate, methyl palmitate, diethylphthalate, ethanol,\ud hexane, acetic acid, hexanoic acid, palmitic acid, γ-kutyrolactone,\ud N-furfuryl pyrrole, N-furfuryl pyrrole-2-aldehyde, 2-acetyl pyrrole,\ud pyrrole-2-aldehyde, 4-vinyl-2-methoxyphenol, 4-vinylphenol, and\ud vanillin. Another 20 compounds were tentatively identified on the\ud basis of their mass spectra. These were 2, 3, 5-trimethyl pyrazine,\ud 2-acetyl pyrazine, (5-methyl-2-furyl)-(2 furyl)-methane, 5-methyl-\ud 2-acetyl furan, bi-(5-methyl-2-furyl)-methane, 4-hydroxy-2, 5-dimethyl-3 (2H)-furanone, heptanal, ethyl formate, pyridine, thiazole,\ud benzothiazole, ethylbenzene, a dichlorobenzene, N-ethylpyrrole-\ud 2-aldehyde, N-isoamyl-pyrrole-2-aldehyde, 5-methylpyrrole-\ud 2-aldehyde, 2-formyl-5-methylthiophene, 2-ethyl-5-butylthiophene,\ud phenol, and 2-methoxyphenol.\ud It is believed that pyrazines, furans, carbonyls, and phenolic\ud compounds make important contributions to the flavor and aroma of popcorn. The presence of many of the compounds identified can be\ud explained by their production during popping from precursors in the\ud popcorn kernels by Maillard browning reactions, Strecker degradation\ud of amino acids, thermal oxidation and hydrolysis of lipids, and\ud direct thermal degradation of plant constituents