Volatile methoxybenzene compounds in grains with off-odors

More than 20 volatile methoxybenzene compounds were found in a set of 745 c orn, sorghum, soybean, and wheat samples obtained from official grain inspe ctors. Most samples containing methoxybenzenes were off-odor. By using an a utosampler, volatiles were purged from whole grain at 80 degrees C, collect ed on Tenax, and then thermally desorbed and transferred to a gas chromatog raph-mass spectrometer for separation and identification. Use of an infrare d detector aided identification of some compounds, especially isomers with similar mass spectra. Samples with insect odor had 1,4-dimethoxybenzene and its 2-methyl, 2-ethyl, and 2-methoxy derivatives that appeared to be deriv ed from 1,4-quinones, which are known (except for a-methoxy) defensive secr etions of Tribolium insects. Samples with mostly musty, sour, and/or smoke odors commonly contained methoxybenzene anti 1,2-dimethoxybenzene along wit h their C-ethyl and 4-ethenyl derivatives, 4-chloro-1-methoxybenzene, and/o r a-methoxyphenol and its 4-ethyl derivative. Other methoxybenzenes were al so found, including methoxy derivatives of other phenols and N-heterocyclic compounds. Go-occurrences and correlations of levels of some compounds wer e also reported to indicate relationships with odors and inter-relationship s among compounds.