Volatile methoxybenzene compounds in grains with off-odors

More than 20 volatile methoxybenzene compounds were found in a set of 745 corn, sorghum, soybean, and wheat samples obtained from official grain inspectors. Most samples containing methoxybenzenes were off-odor. By using an autosampler, volatiles were purged from whole grain at 80 degrees C, collected on Tenax, and then thermally desorbed and transferred to a gas chromatograph-mass spectrometer for separation and identification. Use of an infrared 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 derived from 1,4-quinones, which are known (except for a-methoxy) defensive secretions of Tribolium insects. Samples with mostly musty, sour, and/or smoke odors commonly contained methoxybenzene anti 1,2-dimethoxybenzene along with their C-ethyl and 4-ethenyl derivatives, 4-chloro-1-methoxybenzene, and/or a-methoxyphenol and its 4-ethyl derivative. Other methoxybenzenes were also found, including methoxy derivatives of other phenols and N-heterocyclic compounds. Go-occurrences and correlations of levels of some compounds were also reported to indicate relationships with odors and inter-relationships among compounds.