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At least 991 records · Page 55Linked to original sources
PubMed2006

Chemical characterization of oak heartwood from Spanish forests of Quercus pyrenaica (Wild.). Ellagitannins, low molecular weight phenolic, and volatile compounds.

The need for new sources of quality wood supply for cooperage has led to looking into the possibility of utilizing Quercus pyrenaica Wild. oak, a species native to the Iberian peninsula, as an alternative to other European (Quercus robur and Qurecus petraea) and American (Quercus alba) oaks. The low molecular weight phenolic composition, ellagitannins, and volatile compounds (including a wide range of compound families such as volatile phenols, furanic compounds, lactones, phenyl ketones, other lignin-derived compounds, and volatile compounds related to off-flavors) of green heartwood from Spanish forest regions were studied by HPLC and GC, in order to know its enological characteristics. The chemical composition of Q. pyrenaica is similar to that of other species commonly used in cooperage to make barrels, showing only quantitative differences that were more significant with respect to American than to French species. The four provenance regions studied showed similar chemical composition, with high variability among individuals, often higher than the variability among regions of provenance, but in line with that described in other European and American oak woods. Therefore, this species must be considered to be suitable for aging wine.

Chromatography, High Pressure Liquid↗
PubMed1999

Use of fiber interface direct mass spectrometry for the determination of volatile flavor release from model food systems.

Described in this paper is a fiber interface direct headspace mass spectrometric system for the real-time measurement of flavor release. The system was optimized for the detection of the garlic aroma volatile, diallyl disulfide, from water. Parameters investigated included interface temperature, flow rate through the fiber, flow rate through the sample vessel, and sample stir rate. The delay time for detection of sample after introduction into the sample vessel was determined as 43 s. The system proved to be reliable and robust with no loss in sensitivity or contamination of the mass spectrometer over a 6 month period. The technique was applied to a homologous series of aliphatic alcohols from C(2) to C(7). Results showed that as polarity decreased with increasing chain length the release of volatile into the headspace was faster and gave a higher maximum intensity. Release of the garlic aroma volatile from different commercial mayonnaise products clearly showed a decrease in the release of diallyl disulfide as fat content increased. These results demonstrate the potential of using this technique as a tool for understanding the complex interactions that occur between flavor compounds and the bulk food matrix.

Alcohols↗
PubMed1999

Effect of superficial scald suppression by diphenylamine application on volatile evolution by stored Cortland apple fruit.

Cortland apple fruit (Malus x domestica Borkh.) stored for 120-140 days in air at 0 degrees C were warmed to 22 degrees C and held for 8 days. A portion of the fruit was dipped in a solution of diphenylamine (DPA) at harvest to prevent scald development. Scald occurred only in those fruit not treated with DPA, and its development was accelerated after transfer to 22 degrees C. Ester production from apple fruit tended to increase from day 0 to day 6 of poststorage holding and declined thereafter in both treatments. However, ester production in scald-developing fruit was reduced by approximately 50%. The reduction in volatile production remained relatively constant during the rapid development of scald symptoms. Furthermore, the reduction in volatile production appeared to be independent of respiration and ethylene production. Production of esters derived from hexanol was most reduced in fruit developing scald, with hexyl 2-methylbutanoate production being reduced approximately 15-fold. Interestingly, the production of methyl butanoate was detected only in scalding fruit. alpha-Farnesene production in fruit developing scald was reduced 43% compared with DPA-treated fruit. In contrast, the primary volatile oxidation product of alpha-farnesene, 6-methyl-5-hepten-2-one (MHO), was present only in fruit developing scald. The data suggest that inhibition of ester production may occur as a result of the physiological changes associated with susceptibility to, rather than expression of, scald symptoms.

Diphenylamine↗
PubMed1999

Volatile components in crabmeats of Charybdis feriatus.

The volatile components of different meats (legs with claws, body, and carapace) of a popularly consumed edible crab in Asia, Charybdis feriatus, were investigated. Samples were extracted by simultaneous steam distillation-solvent extraction and analyzed by gas chromatography/mass spectrometry. Among 177 compounds detected, 130 were positively identified. Seventy-six compounds were previously reported in other crab species. A greater number of naphthalenes were detected in this crab compared with other crabs in the literature. Aromatic compounds, alcohols, and sulfur-containing compounds were the three predominant groups with >15 components. Carapace tissue contained a greater number of volatile components in each group, except for sulfur-containing compounds. Most of the common components in the leg meat and the body meat were found at similar levels (p > 0.05). Carapace tissue generally had the highest quantity of common components among the meats. The higher levels of volatile components present in the carapace tissue might account for its stronger flavor compared with the other meats. Furthermore, the higher number of aldehydes and lower number of sulfur-containing compounds detected in the carapace meat might contribute to its unique flavor.

Animals↗
PubMed1999

Volatile compounds from potato-like model systems.

The volatile reaction products of aqueous mixtures comprising combinations of methionine, glucose, linoleic acid, and starch heated in a modified Likens-Nickerson apparatus were extracted and analyzed by gas chromatography-mass spectrometry (GC-MS). The majority of volatile compounds were formed from linoleic acid degradation, hexanal, 2,4-decadienal, and 2-pentylfuran being identified in the greatest amounts. Dimethyl disulfide and dimethyl trisulfide were detected in every system containing methionine. 3-(Methylthio)propanal (methional) and other sulfur compounds were detected when methionine was heated with another precursor. No binding of volatile compounds to starch was observed; rather, starch appeared to act as an additional source of reactive carbohydrate. Almost all the components identified have been identified among the aroma components of cooked potato. No pyrazines, pyridines, or thiazoles were identified, probably due to the relatively low temperature/high moisture conditions.

Cooking↗
PubMed1999

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.

Chemistry Techniques, Analytical↗
PubMed1999

Volatile release from aqueous solutions under dynamic headspace dilution conditions.

Static equilibrium was established between the gas phase (headspace) and an unstirred aqueous phase in a sealed vessel. The headspace was then diluted with air to mimic the situation when a container of food is opened and the volatiles are diluted by the surrounding air. Because this first volatile signal can influence overall flavor perception, the parameters controlling volatile release under these conditions are of interest. A mechanistic model was developed and validated experimentally. Release of compounds depended on the air-water partition coefficient (K(aw)) and the mass transport in both phases. For compounds with K(aw) values <10(-)(3), K(aw) was the factor determining release rate. When K(aw) was >10(-)(3), mass transport in the gas phase became significant and the Reynolds number played a role. Because release from packaged foods occurs at low Reynolds numbers, whereas most experiments are conducted at medium to high Reynolds numbers, the experimentally defined profile may not reflect the real situation.

Food Handling↗
PubMed2000

Volatile changes during dehydration of d'Agen prunes.

Solid phase microextraction (SPME) was used in conjunction with GC-MS to monitor the changes in some major volatile flavors during drying of plums. The aroma profile was significantly modified during the process and substantial loss of the original volatile flavors was observed. The generation of some compounds was shown to be due to the thermal decomposition of carbohydrates. This paper discusses the importance of aroma profiling in detecting the progress of the chemical (degradation) reactions and identifying marker volatiles in quality control of the product.

Fruit↗
PubMed2000

Frozen storage effects on anthocyanins and volatile compounds of raspberry fruit.

The quantitative and qualitative evolution of the anthocyanins and volatile compounds of four raspberry cultivars (cvs. Heritage, Autumn Bliss, Zeva, and Rubi) growing in Spain were analyzed raw, just frozen, and during long-term frozen storage at -20 degrees C for a 1 year period. HS-SPME coupled with GC-MS and HPLC techniques were employed to study the evolution of the volatile compounds and the individual anthocyanins, respectively. The volatile aroma composition changes produced by the freezing process and long-term frozen storage were minimal. Only a significant increase in extraction capacity was obtained for alpha-ionone (27%) and for caryophyllene (67%) in Heritage at 12 months of storage. The stability of anthocyanins to freezing and frozen storage depends on the seasonal period of harvest. Heritage and Autumn Bliss (early cultivars) were less affected by processing and long-term frozen storage (1 year), and the total pigment extracted showed the tendency to increase 17 and 5%, respectively. Rubi and Zeva (late cultivars) suffered a decreased trend on the total anthocyanin content of 4% for Rubi and 17.5% for Zeva. Cyanidin 3-glucoside most easily suffered the degradative reactions that take place during processing and the storage period.

Anthocyanins↗
PubMed2001

Comparison of cultivars of ornamental crop Gerbera jamesonii on production of spider mite-induced volatiles, and their attractiveness to the predator Phytoseiulus persimilis.

We investigated whether volatiles produced by spider mite-damaged plants of four gerbera cultivars differ in attractiveness to Phytoseiulus persimilis, a specialist predator of spider mites, and how the mite-induced odor blends differ in chemical composition. The gerbera cultivars differed in resistance, as expressed in terms of spider mite intrinsic rate of population increase (rm). In order of increasing resistance these were Sirtaki, Rondena, Fame, and Bianca. To correct for differences in damage inflicted on the cultivars, we developed a method to compare the attractiveness of the blends, based on the assumption that a larger amount of spider mite damage leads to higher attraction of P persimilis. Spider mite-induced volatiles of cultivars Rondena and Bianca were preferred over those of cultivar Sirtaki. Spider mite-induced volatiles of cultivars Sirtaki and Fame did not differ in attractiveness to P. persimilis. Sirtaki plants had a lower relative production of terpenes than the other three cultivars. This was attributed to a low production of cis-alpha-bergamotene, trans-alpha-bergamotene, trans-beta-bergamotene, and (E)-beta-farnesene. The emission of (E)-beta-ocimene and linalool was lower in Sirtaki and Fame leaves than in Bianca and Rondena. The importance of these chemical differences in the differential attraction of predatory mites is discussed.

Animals↗
PubMed2002

Learning of herbivore-induced and nonspecific plant volatiles by a parasitoid, Cotesia kariyai.

Learning of host-induced plant volatiles by Cotesia kariyai females was examined with synthetic chemicals in a wind tunnel. Wasps were preconditioned by exposure to volatiles and feces simultaneously. A blend of four chemicals, geranyl acetate, beta-caryophyllene, (E)-beta-farnesene, and indole, which are known to be specifically released from plants infested by host larvae Mythimna separata (host-induced blend), elicited a response in naive C. kariyai, but did not enhance the response after conditioning. A blend of five chemicals, (E)-2-hexenal, (Z)-3-hexen-1-ol, (Z)-3-hexen-1-yl acetate, beta-myrcene, and linalool, which are known to be released not only from plants infested by the host larvae, but also from artificially damaged plants or undamaged ones (unspecific blend), elicited little response in naive wasps, but significantly enhanced the wasps' response after conditioning. With a blend of the above nine chemicals, wasps could learn the blend at lower concentrations than they did in the nonspecific blend. Hence, both the host-induced and nonspecific volatile compounds appear to be important for C. kariyai females to learn the chemical cues in host location.

Animals↗
PubMed2002

Allelopathic potential and chemical constituents of volatiles from Ageratum conyzoides under stress.

The allelopathic potential of Ageratum conyzoides was investigated under different environmental stress conditions, including nutrient deficiency. physical damage, 2.4-D treatment, competition with Bidens pilosa, infection with Erysiphe cichoracearum, and feeding by Aphiids gossypii. The inhibitory effects of A. conyzoides volatiles on peanut (Arachis hypogaea), redroot amaranth (Amaranthus retroflexus), cucumber (Cucumis sativus), and ryegrass (Lolium multiforum) increased when plants were grown under nutrient-deficient conditions or in competition with B. pilosa; however, there was no difference with physical damage or 2.4-D treatment. Phytoinhibitory effects decreased under fungal infection and aphid feeding. Volatiles from A. conyzoides plants infected with E. cichoracearum or exposed to A. gossypii feeding inhibited or killed fungi and insects. Precocenes and their derivatives, monoterpenes, and sesquiterpenes were the major volatile components of A. conyzoides.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2002

Volatile compounds in anal gland of Siberian weasels (Mustela sibirica) and steppe polecats (M. eversmanni).

The volatile constituents in anal gland secretions of two sympatric Mustela species, the Siberian weasel (M. sibirica) and steppe polecat (M. eversmanni), were studied by the headspace technique, followed by gas chromatography-mass spectrometry (GC-MS) analysis. Nine sulfur-containing compounds were identified. They were 2,2-dimethylthietane, (Z)- or (E)-2,4-dimethylthietane, (E)-2,3-dimethylthietane, 2-ethylthietane, (E)-2-ethyl-3-methylthietane, (Z)-2-ethyl-3-methylthietane, 2-propylthietane, 3,3-dimethyl-1,2-dithiacyclopentane, and (Z)-3,4-dimethyl-2,2-dithiacyclopentane. Among them, (E)-2-ethyl-3- methylthietanes, (Z)-2-ethyl-3-methylthietanes, and (Z)-3,4-dimethyl-1,2-dithiacyclopentane were present in the polecat but not in the weasel. The predominant compound was 2,2-dimethylthietane in the weasel and (E)- or (Z)-2,4-dimethylthietane in the polecat. These differences were consistent between the two species, regardless of sex and age and, therefore, could possibly be used for species recognition. In the weasel, 2-ethylthietane was found only in the female, and the relative abundance of several compounds was significantly different between males and females. In the polecat, although no sex-specific volatile compounds were found, males and females differed in the relative abundance of several of the compounds. In both species, the relative abundance of some compounds varied with age. We conclude that these volatile compounds can be used to communicate information about species, sex, and age.

Anal Canal↗
PubMed2002

Purine metabolizing capability of Enterobacter agglomerans affects volatiles production and attractiveness to Mexican fruit fly.

We investigated two strains of Enterobacter agglomerans that differ in their ability to metabolize uric acid for (1) attractiveness to sugar-fed Mexican fruit flies, and (2) production of volatile chemicals that may be responsible for the attractiveness. The two strains were cultured on a medium that contained uric acid as the primary nitrogen source to simulate bird feces, a natural substrate for this bacterium. Active cultures of both strains were more attractive than uninoculated uric acid medium to both sexes of sugar-fed flies in wind-tunnel bioassays. The uricase(+) strain was more attractive than the uricase(-) strain to males and to females <9 days old, but not to older females. Volatiles found by solid-phase microextraction in greater amounts in headspace above active cultures of both strains than above uninoculated medium were ammonia, dimethyldisulfide, 3-methylbutanol, 2-phenylethanol, 2,5-dimethylpyrazine, and trimethylpyrazine. The uricase(+) strain produced more ammonia, dimethyldisulfide, and trimethylpyrazine than the uricase(-) strain. An additional chemical, 3-hydroxybutanone, appears to be produced exclusively by the uricase(+) strain. The uricase(-) strain produced more 2-phenylethanol than the uricase(+) strain. Differences in volatiles are consistent with the generally greater attractiveness of the uricase(+) strain compared with the uricase(-) strain as ammonia, 3-hydroxybutanone, and trimethylpyrazine have been demonstrated attractive to sugar-fed Mexican fruit flies.

Animals↗
PubMed2003

Volatiles from whitefly-infested plants elicit a host-locating response in the parasitoid, Encarsia formosa.

The blend of volatile compounds emitted by bean plants (Phaseolus vulgaris) infested with greenhouse whitefly (Trialeurodes vaporariorum) has been studied comparatively with undamaged plants and whiteflies themselves. Collection of the volatiles and analysis by gas chromatography revealed more than 20 compounds produced by plants infested with whitefly. Of these, 4 compounds, (Z)-3-hexen-1-ol, 4,8-dimethyl-1,3,7-nonatriene, 3-octanone, and one unidentified compound were emitted at higher levels than from the undamaged control plants. Synthetic (Z)-3-hexen-1-ol, 4,8-dimethyl-1,3,7-nonatriene, or 3-octanone all elicited a significant increase in oriented flight and landing on the source by the parasitoid, Encarsia formosa, in wind tunnel bioassays. Two-component mixtures of the compounds and the three-component mixture all elicited a similar or, in most cases, a better response by the parasitoid, the most effective being a mixture of (Z)-3-hexen-1-ol and 3-octanone. These results demonstrate that E. formosa uses volatiles from the plant-host complex as olfactory cues for host location.

Animals↗
PubMed2003

Antennal responses of the two host races of the larch bud moth, Zeiraphera diniana, to larch and cembran pine volatiles.

The larch bud moth (LBM) Zeiraphera diniana Guenée causes defoliation on larch in the Alps at 8- to 10-year intervals, after which populations crash. There are two LBM host races, one on larch and the other on cembran pine. These host races are morphologically indistinguishable as adults but they differ genetically in larval color types. Furthermore, females of each host race produce distinct pheromone blends and show oviposition preferences for their respective hosts. It is not clear to what extent host choice contributes to assortative mating in the LBM. Here, we compare the olfactory sensitivities of the two host races to the odors of fresh foliage of the host plants using the electroantennogram (EAG) technique, and the responses of the two host races to volatiles collected from the two host plants as analyzed by gas-chromatography-linked antennographic detection (GC-EAD). Both sexes of the larch and cembran host races show the same EAG responses to vapors of fresh larch and cembran pine foliage. Fifteen plant volatiles identified as chemostimuli by GC-EAD from larch and cembran pine odors elicited the same antennogram responses from the two host races. However, the GC-EAD analyses indicate that the number and quantity of chemostimuli emanating from each host plant is different. It is, therefore, most probably the array of olfactory receptors responding to the bouquet of volatiles unique to each host plant that underlies the host preferences of the two races. What remains open is the extent to which the similarity of the olfactory systems may contribute to cross-attraction. The fact that LBM individuals with intermediate characteristics between the two host races exist, suggests that olfactory perception does not hinder gene flow and contributes to sustained genetic diversity within the species Z. diniana.

Animals↗
PubMed2004

Host plant volatiles synergize response to sex pheromone in codling moth, Cydia pomonella.

Plant volatile compounds synergize attraction of codling moth males Cydia pomonella to sex pheromone (E,E)-8,10-dodecadien-1-ol (codlemone). Several apple volatiles, known to elicit a strong antennal response, were tested in a wind tunnel. Two-component blends of 1 pg/min codlemone and 100 pg/min of either racemic linalool, (E)-beta-farnesene, or (Z)-3-hexen-1-ol attracted significantly more males to the source than codlemone alone (60, 58, 56, and 37%, respectively). In comparison, a blend of codlemone and a known pheromone synergist, dodecanol, attracted 56% of the males tested. Blends of pheromone and plant volatiles in a 1:100 ratio attracted more males than 1:1 or 1:10,000 blends. Adding two or four of the most active plant compounds to codlemone did not enhance attraction over blends of codlemone plus single-plant compounds. Of the test compounds, only farnesol was attractive by itself; at a release rate of 10,000 pg/min, 16% of the males arrived at the source. However, attraction to a 1:10,000 blend of codlemone and farnesol (42%) was not significantly different from attraction to codlemone alone (37%). In contrast, a codlemone mimic, (E)-10-dodecadien-1-ol, which attracted 2% males by itself, had a strong antagonistic effect when blended in a 1:10,000 ratio with codlemone.

Acyclic Monoterpenes↗
PubMed1997

Energy, volatile production, and climatic effects of the Chicxulub Cretaceous/Tertiary impact.

A comprehensive analysis of volatiles in the Chicxulub impact strongly supports the hypothesis that impact-generated sulfate aerosols caused over a decade of global cooling, acid rain, and disruption of ocean circulation, which contributed to the mass extinction at the Cretaceous/Tertiary (K/T) boundary. The crater size, meteoritic content of the K/T boundary clay, and impact models indicate that the Chicxulub crater was formed by a short period comet or an asteroid impact that released 0.7-3.4 x 10(31) ergs of energy. Impact models and experiments combined with estimates of volatiles in the projectile and target rocks predict that over 200 gigatons (Gt) each of SO2 and water vapor, and over 500 Gt of CO2, were globally distributed in the stratosphere by the impact. Additional volatiles may have been produced on a global or regional scale that formed sulfate aerosols rapidly in cooler parts of the vapor plume, causing an early, intense pulse of sulfuric acid rain. Estimates of the conversion rate of stratospheric SO2 and water vapor to sulfate aerosol, based on volcanic production of sulfate aerosols, coupled with calculations of diffusion, coagulation, and sedimentation, demonstrate that the 200 Gt stratospheric SO2 and water vapor reservoir would produce sulfate aerosols for 12 years. These sulfate aerosols caused a second pulse of acid rain that was global. Radiative transfer modeling of the aerosol clouds demonstrates (1) that if the initial rapid pulse of sulfate aerosols was global, photosynthesis may have been shut down for 6 months and (2) that for the second prolonged aerosol cloud, solar transmission dropped 80% by the end of first year and remained 50% below normal for 9 years. As a result, global average surface temperatures probably dropped between 5 degrees and 31 degrees K, suggesting that global near-freezing conditions may have been reached. Impact-generated CO2 caused less than 1 degree K greenhouse warming and therefore was insignificant compare to the sulfate cooling. The magnitude of sulfate cooling depends largely upon the rate of ocean mixing as surface waters cool, sink, and are replaced by upwelling of deep ocean water. This upwelling apparently drastically altered ocean stratification and circulation, which may explain the global collapse of the delta 13C gradient between surface and deep ocean waters at the K/T boundary.

Acid Rain↗