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J Agric Food Chem. 2000 Sep;48(9):4279-89.

Volatile methoxybenzene compounds in grains with off-odors.

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U.S. Grain Marketing Research Laboratory, Grain Marketing and Production Research Center, Agricultural Research Service, U.S. Depatment of Agriculture, 1515 College Avenue, Manhattan, Kansas 66502, USA.


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 2-methoxy) defensive secretions of Tribolium insects. Samples with mostly musty, sour, and/or smoke odors commonly contained methoxybenzene and 1, 2-dimethoxybenzene along with their 4-ethyl and 4-ethenyl derivatives, 4-chloro-1-methoxybenzene, and/or 2-methoxyphenol and its 4-ethyl derivative. Other methoxybenzenes were also found, including methoxy derivatives of other phenols and N-heterocyclic compounds. Co-occurrences and correlations of levels of some compounds were also reported to indicate relationships with odors and inter-relationships among compounds.

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