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 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.

Use of an autosampler for dynamic headspace extraction of volatile compounds from grains and effect of added water on the extraction.

An autosampler attached to a purge and trap instrument was used to aid routine analyses of grain samples for volatile compounds associated with off-odors. Trapped volatiles were transferred to a gas chromatograph/mass spectrometer instrument for separation and detection. Dynamic extraction of volatiles from approximately 18 g of whole grain at 80 degrees C was accomplished by purging helium through a sample vial with a Teflon-lined septum on each end. The autosampler automatically added internal standard to the sample before purging began, which required the addition of 1 mL of water for complete transfer of the standard to the sample. The added water enhanced extraction of 1-octen-3-ol, 1-octen-3-one, and some other compounds from soybeans but not from starchy grains such as corn and wheat. Addition of a free radical scavenger, such as citric acid, greatly diminished the recovery of 1-octen-3-ol and 1-octen-3-one from soybeans.

Volatiles obtained from whole and ground grain samples by supercritical carbon dioxide and direct helium purge methods: observations on 2,3-butanediols and halogenated anisoles.

Volatile compounds were obtained from whole and ground grain samples by two methods. In the supercritical fluid extraction (SFE) method, volatiles were extracted from the grain with supercritical carbon dioxide, trapped at -78 degrees C, and then transferred via a purge-and-trap instrument to a gas chromatograph with mass and infrared detectors (GC-MS/IR) for separation and identification. In the direct-helium-purge method (DHP), volatiles were purged directly from the grain into the purge-and-trap instrument for subsequent transfer to the GC-MS/IR system. With SFE, extraction of volatiles was favored by ground grain, low pressures (

Deoxynivalenol-contaminated wheat in swine diets.

Two studies were conducted using Fusarium graminearum-infected (scabby) wheat containing 6.8 ppm deoxynivalenol (DON), commonly called vomitoxin, substituted for normal wheat in starter pig diets to give varying levels of DON. After 3 wk on experimental treatments, one-half of the pigs in trial one were sacrificed to evaluate the effects of DON on heart, kidney, spleen and liver. Analyses for DON residues in these tissues were also performed. The remaining 16 pigs were placed on a conventional diet for 4 wk to evaluate effects of DON on subsequent animal performance. A different sample of scabby wheat containing 4.9 ppm of DON was substituted for sorghum grain in growing-finishing pig diets to give varying concentrations of DON. At the end of the 42-d feeding period, eight pigs were slaughtered to evaluate the effects of DON on selected tissues. Results of the three trials suggest that feed intake was reduced when DON concentrations in the swine diets neared or exceeded 1 ppm. No apparent signs of disease, including vomiting, were observed in experimental animals. Histological evaluation revealed no significant lesions or abnormalities related to DON ingestion in tissues examined. Traces of DON (8 to 28 ppb, wet weight) were found in kidney, liver, spleen and heart of starter pigs consuming the diets containing DON up to time of slaughter. No DON was found in tissues of growing-finishing pigs that were withdrawn from feed about 12 h before slaughter.

Laser fluorometric determination of aflatoxin B1 in corn.

A 2-step chromatographic separation, using both thin layer chromatography (TLC) and high pressure liquid chromatography (HPLC), in conjunction with the high sensitivity of laser fluorometry permits extension of the detection limits of aflatoxin contamination in corn to 0.1 ppb (microgram/kg) with a 26% root mean square variation. Aflatoxin B1 is extracted from corn with water-methanol and cleaned up by TLC. The recovery of aflatoxin from the TLC plates was linear from 10 to 1000 pg. Aflatoxin B1 is converted to the more highly fluorescent B2A derivative by treatment with 1N HCl. Experiments with aflatoxin B1 standard establish a constant conversion to B2A over approximately 3 orders of magnitude in B1 concentration. An extract of the B2A aflatoxin derivative is injected onto a reverse phase HPLC column. A flowing droplet of eluant is irradiated by an amplitude-modulated 325 nm He-Cd ion laser beam, and fluorescence from the droplet is detected by a lock-in amplifier in phase with the laser modulation. Several chromatograms are presented that demonstrate the capability of this procedure for removing interfering components in the corn extract.

Effect of substrate on metabolite production of Alternaria alternata.

Alternariol and alternariol monomethyl ether are commonly associated with weathered grain sorghum. Production of these metabolites and altenuene by isolates of Alternaria alternata was evaluated on various sterile grain substrates. At 35% moisture content and 25 C, metabolite yields were highest on rice, intermediate on sorghums, and lowest on wheat and yellow corn. Fourteen-to 21-day cultures on milled rice were best in terms of ease of metabolite recovery, even though yields were higher on 28-day cultures of rough and brown rice. Metabolite production was reduced when rice was supplemented with yeast extract or yeast extract plus Czapek-Dox broth.

Simple method for simultaneous detection of aflatoxin and zearalenone in corn.

A method is described for the simultaneous detection of alfatoxin and zearalenone in corn at 5 and 200 ppb, respectively. No evaporation of solvent is required and the procedure is simple enough to be considered for use at marketing locations. The presence of absence of these myocotoxins can be determined in 10-20 min/sample. The procedure involves an initial blender extraction with methanol, partitioning of fat and pigments into 1-1,2-trichlorotrifluoroethane (Freon-113) from an aqueous ammonium sulfate layer, followed by extraction of aflatoxin from the aqueous layer with chlorobenzene. The chlorobenzene extract can be spotted directly onto a thin layer chromatographic plate which requires only 4 min development. Concentrations of aflatoxin and zearalenone can be estimated by visual comparison of sample spots with standards.

Comparison of methods for aflatoxin analysis by high-pressure liquid chromatography.

Reversed-phase columns packed with octadecyl and phenyl reversed phases did not provide adequate separation of aflatoxins. A peculiar adsorption column provided partial separation, i.e. B1 and B2 from G1 andG2, but not B1 from B2 nor G1 from G2. A microparticulate adsorption (7icro-A) column completely separated aflatoxins B1, B2, G1, and G2. Detection was more selective at 350 nm (or 365 nm) than at 254 nm. A Fluoro Monitor Model 1209 detector (Laboratory Data Control Corp.) was more sensitive for aflatoxins G1 and G2 than for B1 and B2. Aflatoxin B1 at the 30-ppb level in yellow corn was detected with the Micro-A column and the 350-nm photometer. The limit of detection was estimated at about 10 ppb.