Leonard M. Libbey

A Paradox Database for GC/MS Data on Components of Essential Oils and Other Volatiles

ABSTRACT An IBM-PC based database has been developed for Kovats indices and major ion fragments in mass spectrometry for essential oil components and other volatiles.

N-Nitrosodimethylamine in beer

Abstract Commercially-available bottled and canned beer was analysed for volatile nitrosamines using a chemiluminescence detector. N -Nitrosodimethylamine, the only volatile nitrosamine found, was detected in 23 of 25 samples analysed. The range of levels was 0–14 ppb (μg/kg) while the mean was 5·9 ppb. The identity of N -nitrosodimethylamine was confirmed by mass spectrometry.

Frontalin in the male mountain pine beetle

Frontalin andexo-brevicomin were identified by GC-MS in air drawn over maleDendroclonus ponderosae Hopk. (MPB) from Oregon that had joined females for 1–2 days in the bark of lodgepole and ponderosa pine logs. Unfed males releasedexo- andendo-brevicomin but not frontalin. These three compounds were not detected in either unfed or fed females. Arrestment of males bytrans-verbenol and terpenes in an olfactory walkway was reduced by the addition of racemic frontalin; production of attractant chirps also diminished. Racemic frontalin also strongly reduced the aggregation of MPB in lodgepole and ponderosa pine stands to sticky traps baited with the aggregation pheromonetrans-verbenol and host terpenes; however, the function of the natural enantiomer of frontalin in MPB is unknown.

1-Methylcyclohex-2-en-1-ol as an aggregation pheromone ofDendroctonus pseudotsugae

Abstract1-Methylcyclohex-2-en-1-ol (1,2-MCH-ol) was synthesized, identified as a compound found in volatiles of the female Douglas-fir beetle, and shown by bioassays to be an aggregation pheromone. 1,2-MCH-ol matches in both GC retention index and mass spectrum a compound released by the female after feeding. 3,3-MCH-ol was also synthesized as a candidate compound; its mass spectrum is presented because published mass spectra are incorrect for this compound. Synthetic 1,2-MCH-ol increased arrestment and stridulation of males in olfactory walkways and increased trap catches of flying beetles. Males were more responsive to 1,2-MCH-ol than females.

Identification and mutagenicity of aflatoxicol-M1 produced by metabolism of aflatoxin B1 and aflatoxicol by liver fractions from rainbow trout (Salmo gairdneri) fed β-naphthoflavone

beta-Naphthoflavone (beta NF) fed to rainbow trout (Salmo gairdneri) at 50 or 500 ppm in the diet, modified the in vitro metabolism of aflatoxin B1 (AFB1) by the postmitochondrial fraction (PMF) of the liver. Production of aflatoxicol (AFL) was significantly less in the 500 ppm beta NF-fed group (33.9 ng/mg protein) than in the control group (45.7 ng/mg protein), aflatoxin M1 production was dependent on the dose of beta NF, being greatest in the 500 ppm beta NF-fed group (48.9 ng/mg protein), intermediate in the 50 ppm beta NF-fed group (3.7 ng/mg protein), and was not detected in controls. A new trout metabolite, 4-hydroxyaflatoxicol (aflatoxicol M1, AFLM1) was also detected in small amounts from in vitro metabolism by liver PMF from beta NF-fed trout. Sufficient quantities of AFLM1 for confirmation of identity by ultraviolet spectra, mass spectra and nuclear magnetic resonance spectra were prepared by biotransformation of AFL using liver microsomes and isolation by HPLC. In a modified Ames mutagen assay with Salmonella typhimurium TA98, ALFM1 was 4.1% as mutagenic as AFB1 in a previous determination. The carcinogenicity of AFLM1 to rainbow trout is expected to be considerably less than that of AFB1.

N-Nitrosodimethylamine in dried dairy products

Abstract Commercially available non-fat dried milk and dried buttermilk were analysed for volatile nitrosamines using a chemiluminescence detector. N-Nitrosodimethylamine, the only volatile nitrosamine that could be confirmed to be present by mass spectrometry, was detected in eight out of nine samples analysed. The range of levels was 0 to 4·5 ppb (μg/kg) while the mean was 1·9 ppb. The identity of N-nitrosodimethylamine was confirmed by mass spectrometry in five of the samples.

POROUS POLYMER TRAPPING FOR GC/MS ANALYSIS OF VEGETABLE FLAVORS

Flavor profiles of canned and frozen whole kernel sweet corn were obtained by entraining the volatile compounds on Porapak Q traps and by subsequent analysis on temperature-programed, 500′ × 0.03″ ID capillary columns (SF-96 or Carbowax 20M). Identification was based on GC/MS data, retention indices (I E s), and retention times. The new compounds identified in canned corn included pyridine, methional, dimethyl sulfoxide, and dimethyl sulfone. Various sulfur, nitrogen, and nitrogen-sulfur heterocyclic compounds were also present as previously mentioned by Libbey et al. (l). Qualitative and quantitative varietal differences were observed in both frozen and canned samples. Many of these compounds were typical of roasted foods, such as nuts or roasted meats, and were not found to any extent in samples of frozen or fresh corn. New compounds found in frozen corn included acetoin, 3-methyl-2-cyclohexenone, and dimethyl sulfone. Various model systems were heated to simulate the canning process of sweet corn. Mixtures of water, corn starch, and sulfur-containing (l) Libbey, L.M., M.E. Morgan, L.A. Hansen, and R.A. Scanlan. Higher-Boiling Volatiles in Canned Whole Kernel Sweet Corn. A.C.S. Atlantic City, N.J. 1975. amino acids produced the most corn-like aromas. Systems containing glutamic acid, asparagine, proline, aspartic acid, and other amino acids produced earthy, parsnip, or vegetable notes. Pyrazines, furans, and thiophenes were among the compounds identified. Other experiments were conducted to elucidate mechanisms of flavor formation and to simulate sweet corn flavor.

Mass spectrometry of the silver nitrate derivatives of cyclopropenoid compounds

Abstract 1,2-dihexylcyclopropene, 1,2-diheptylcyclopropene, 1,2-dioctylcyclopropene, methyl malvalate, and methyl sterculate have been reacted with silver nitrate in methanol to form the corresponding methoxy and ketone derivatives. GLC, IR, and MS data are presented. The mass spectra and a possible method for determining the cyclopropene ring position are discussed.

Sensory and analytical evaluation of beers brewed with three varieties of hops and unhopped beer

SUMMARY Pilot brews made with Hallertauer Mittelfruh, U.S.D.A. 21459, U.S.D.A. 21455 (Mt. Hood), and a beer brewed without hops were evaluated for aroma by a descriptive sensory panel (DSP). The extracts from the beers were evaluated using Osme, a GC olfactometry method: The beer extract samples were injected into the gas chromatograph-olfactometer (GCO) and the effluents evaluated qualitatively and quantitatively by four trained subjects. A time-intensity device connected to an IBM computer was used to record the odor intensities. The samples were analyzed by mass spectrometry to identify the odor active compounds. Sensory profiles of the hopped beers were similar indicating that beers brewed with U.S.D.A. 21455 and U.S.D.A. 21459 contribute “noble” hop aroma.

Isolation and characterization of products from the nitrosation of the alkaloid gramine

The nitrosation of gramine, a tertiary amine alkaloid present in barley malt, was carried out by reaction with sodium nitrite in buffered acetic acid (pH 3.4) for 1 hr at room temperature. Two major non-volatile products of the nitrosation reaction were isolated by preparative HPLC and characterized as indole-3-carboxylic acid and N1-nitroso-3-nitromethylindole. This interpretation was supported by spectral data. The nature of these products indicated that gramine did not undergo nitrosation by the expected mechanism of nitrosative dealkylation. A mechanism is offered to explain the labile nature of the dimethylamino group found in gramine.