Trapping of Aromatic Compounds by Adsorption on Hydrophobic Sorbents

Abstract

Trapping by adsorption on hydrophobic porous polymers was the selected method for removing aromatic compounds from aqueous diluted medium. The study was done with four aromatic compounds which are often found in foods and which play a role in organoleptic qualities at low concentrations: ethyl acetate, 2,5-dimethylpyrazine, 1-octen 3-ol, and-γ-decalactone. Several sorbents were tested: activated carbon and three porous polystyren-type polymers (Porapak Q, Chromosorb 105, and Amberlite XAD-4). Kinetic and equilibrium sorptions were investigated. The adsorption isotherms were determined for the four aromatic and all the adsorbents, and equilibrium data were correlated with a Freundlich or a Langmuir-type of isotherm equation. Kinetic experimental results were simulated for 1-octen 3-ol using an internal-external mass transfer resistance model. Good agreement was observed for the diffusion coefficient in the sorbent in the range of 10^?8cm^2.s^?1.     

Characterization of Volatile Organic Compounds Emitted by Barley (Hordeum vulgare L.) Roots and Their Attractiveness to Wireworms

Root volatile organic compounds (VOCs), their chemistry and ecological functions have garnered less attention than aboveground emitted plant VOCs. We report here on the identification of VOCs emitted by barley roots (Hordeum vulgare L.). Twenty nine VOCs were identified from isolated 21-d-old roots. The detection was dependent on the medium used for root cultivation. We identified 24 VOCs from 7-d-old roots when plants were cultivated on sterile Hoagland gelified medium, 33 when grown on sterile vermiculite, and 34 on non-sterile vermiculite. The major VOCs were fatty acid derived compounds, including hexanal, methyl hexanoate, (E)-hex-2-enal, 2-pentylfuran, pentan-1-ol, (Z)-2-(pentenyl)-furan, (Z)-pent-2-en-1-ol, hexan-1-ol, (Z)-hex-3-en-1-ol, (E)-hex-2-en-1-ol, oct-1-en-3-ol, 2-ethylhexan-1-ol (likely a contaminant), (E)-non-2-enal, octan-1-ol, (2E,6Z)-nona-2,6-dienal, methyl (E)-non-2-enoate, nonan-1-ol, (Z)-non-3-en-1-ol, (E)-non-2-en-1-ol, nona-3,6-dien-1-ol, and nona-2,6-dien-1-ol. In an olfactometer assay, wireworms (larvae of Agriotes sordidus Illiger, Coleoptera: Elateridae) were attracted to cues emanating from barley seedlings. We discuss the role of individual root volatiles or a blend of the root volatiles detected here and their interaction with CO₂ for wireworm attraction.     

Extreme sensitivity of grandisal to acids

Attempted purification of synthetic racemic grandisal1 by silica gel chromatography resulted in severe decomposition. The nature of this reaction was studied on silica gel and in an ether solution ofp-toluenesulfonic acid. The same products resulted from both reaction systems, although in different ratios. Five racemic, rearrangement products were isolated by preparative GC and identified as follows: (1RS, 3SR, 6RS)-1-methyl-5-methylenebicyclo[4.2.0]octan-3-ol (4); (1RS, 3RS, 6RS)-1-methyl-5-methylenebicyclo[4.2.0]octan-3-ol (5); (1RS,3RS,6RS)-1,5-dimethylbicyclo[4.2.0]oct-4-en-3-ol (6); (1RS,3SR,6RS)-1,5-dimethylbicyclo[4.2.0]oct-4-en-3-ol(7); and 3-methyl-7-methylenecyclooct-3-en-l-ol (8). The stereochemical assignments are based on our proposed mechanism, which also accounts for all products observed. The racemic bicyclic enone (3) was a by-product of grandisol (2) oxidation.     

Electroantennogram response of alfalfa seed chalcid,Bruchophagus roddi (Hymenoptera: Eurytomidae) to host- and nonhost-plant volatiles

The alfalfa seed chalcid (ASC),Bruchophagus roddi, is a monophagous pest of alfalfa that parasitizes developing seeds. To further understand the olfactory basis of host-plant recognition by ASCs, we recorded electroantennograms (EAGs) from females and males to 39 volatiles from both alfalfa and red clover. The chemoreceptive sensitivity of ASCs was selective for certain general classes of compounds, defined by their carbon-chain length (C₆ and C₈), structure (aliphatics and phenolics), isomerism, and/or functional group (acetates, ketones, and alcohols). The compounds that elicited the largest EAGs were ranked as follows: (Z)-3-hexenyl acetate > hexyl acetate acetophenone octan-3-one methyl salicylate > octan-3-ol > oct-1-en-3-one > oct-1-en-3-ol (E)--ocimene (Z)- and (E)-3-hexen-1-ols. Over half the test compounds elicited significantly different responses between the sexes, and female antennal responses exceeded those of males for twice the number of these volatiles. Relationships of the tested volatiles to host-plant composition, EAG responses, and ASC behaviors showed no consistent correlations. However, nearly all of the host-plant volatiles known to stimulate behavioral activity also elicited moderate to potent EAG responses.     

Structure-Activity Relationships of Alkylpyrazine Analogs and Fear-Associated Behaviors in Mice

Our previous studies identified alkyl pyrazine analogs in wolf urine that act as novel kairomones and induce a series of fear-associated behaviors in mice. A mixture of these alkyl pyrazines also effectively suppressed the approach of deer to a feeding area, and animals that did approach the marked area exhibited fear-associated behaviors. To investigate structure-activity relationships of alkyl pyrazines, four fear-associated behaviors - freezing, locomotion activity, odor investigation, and avoidance - were measured in experiments on female C57BL/6 J mice. Of the 17 compounds tested, 2,3-diethylpyrazine, 3-ethyl-2,5-dimethylpyrazine, and 3-ethyl-2,5-dimethylpyrazine induced all four fear-associated behaviors. 2,3,5-Trimethylpyrazine also induced three of the fear-associated behaviors, but did not decrease locomotion. Multivalent analysis of behaviors clearly demonstrated that these four compounds formed an independent cluster and were the most active. Structure-activity relationships revealed that active alkyl pyrazines inducing all four fear-associated behaviors had methyl or ethyl group(s), but not longer carbon chains, and alkyl side chains consisting of four carbon atoms in total were present in the most potent analogs. This study is the first experimental investigation of structure-activity relationships between alkyl pyrazine analogs and fear-associated behaviors in mice.     

维药小茴香根皮乙酸乙酯部位化学成分研究

采用硅胶柱色谱、Sephadex LH-20和重结晶等分离手段对维药小茴香根皮中乙酸乙酯提取部分进行分离纯化,通过1H NMR、13C NMR进行结构鉴定。结果表明,从乙酸乙酯提取部分分离5个化合物,分别鉴定为莳萝脑(1)、邻苯二甲酸丁基异丁基二酯(2)、镰叶芹二醇(3)、β-谷甾醇(4)、甘油酸(5)。该研究为了解维药茴香根皮的药用价值提供了研究基础。     

A comparative study of potent odorants in peanut,hazelnut, and pumpkin seed oils on the basis of aroma extract dilution analysis (AEDA) and gas chromatography-olfactometry of headspace samples (GCOH)

Potent odorants in commercially processed peanut, hazelnut, and pumpkin seed oils were evaluated by the application of aroma extract dilution analysis (AEDA) and gas chromatography-olfactometry of headspace samples (GCOH). AEDA revealed 38, 28 and 27 odour-active compounds in peanut, hazelnut, and pumpkin seed oils, respectively. Fifteen odorants were present in all oils; two of them showed the highest flavour dilution factor (FD-factor): 2-ethyl-3,5-dimethylpyrazine and 2,3-diethyl-5-methylpyrazine. Application of GCOH led to the identification of 21, 24, and 24 odorants in peanut, hazelnut, and pumpkin seed oils, respectively. Nine of them were found in all oils: acetaldehyde, propanal, 2-methylpropanal, 2- and 3-methylbutanal, 2-ethyl-3,5-dimethylpyrazine, 2,3-diethyl-5-methylpyrazine, (E)-2-nonenal and vanillin. The following odorants appeared with relative high FD-factors in the headspace of a single oil: 1-penten-3-one in peanut, 5-methyl-(E)-2-hepten-4-one (Filbertone) in hazelnut, (Z)-4-heptenal and 3-ethyl-2,5-dimethylpyrazine in pumpkin seed oil.     

Synthesis of a Versatile Prostaglandin Intermediate by Ozonization of endo-cis-Bicyclo[3.3.0]oct-6-en-2-ol

The ozonization of endo-cis-bicyclo[3.3.0]oct-6-en-2-ol ( 1 ) in methanol followed by reduction with dimethyl sulfide in the presence of traces of an acid yields in a one-pot procedure an anomeric mixture of 3-exo-methoxy- and 3-endo-methoxy-2-oxabicyclo[3.3.0]octane-6-endo-carbaldehyde ( 3a and 3b ) in a ratio of 9:1. This mixture is converted by base catalyzed epimerization in an overall yield of about 65% into a mixture of the anomeric 6-exo-aldehydes 5a and 5b , a versatile starting material for the synthesis of prostaglandins of the PG₂-type.     

Asymmetric Hydrogenation of Amino Acid Precursors promoted by a new type of cholesterol amphiphiles: Investigation of aggregation behaviour and stereoselective effects

Reaction of 2-hydroxyethanesulfonic acid sodium salt, 3-hydroxypropanesulfonic acid sodium salt or 2-aminoethanesulfonic acid sodium salt with cholest-5-en-3β-ol-3-chloroformate yields the chiral amphiphilic compounds 2-(cholest-5-en-3β)oxy-carbonyloxy-ethanesulfonic acid sodium salt 1 , 2-(cholest-5-en-3β)oxy-carbonyloxy-propanesulfonic acid sodium salt 2 and 2-(cholest-5-en-3β)oxy-carbonylaminoethanesulfonic acid sodium salt 3 , respectively. Another chiral amphiphile 2-(cholest-5-en-3β)oxy-carbonylethanesulfonic acid sodium salt 4 was synthesized by treating cholest-5-en-3β-ol with sulfopropionic acid anhydride. The surfactants form vesicles in aqueous solutions, as shown by electron microscopy. Stepwise destruction of these vesicles by addition of ethanol or methanol was proved by Circular Dichroism (CD) measurements. Especially compound 3 shows pronounced induced CD effects with the achiral dye 3,6-diamino-acridine-sulfate (proflavine). The synthesized chiral amphiphiles were used in the asymmetric hydrogenation reaction of methyl (Z)-α-acetamidocinnamate. In the case of an achiral rhodium complex as catalyst the prepared surfactants 1, 2 , and 4 are able to provide an enantiomer excess by themselves. The best ee-value reached was 8.5% methyl (R)-N-acetylphenyl-alaninate in connection with compound 4 .     

亚油酸去氧氟尿苷酯的合成与表征

采用DCC/DMAP催化剂,亚油酸（LA）与去氧氟尿苷（FUdR）酯化合成亚油酸去氧氟尿苷酯。其反应条件为：底物摩尔比n（LA）∶n（FUdR）=1∶1.2,室温反应18 h。用硅胶柱层析分离方法,以V（石油醚）∶V（乙酸乙酯）=3∶1溶剂体系作流动相分离得到目标产物,并用核磁共振及质谱对其表征。结果表明,目标产物为亚油酸去氧氟脲苷酯。     

Triterpene alcohols, 4-methylsterols and 4-desmethylsterols of eggplant seed oil: A new phytosterol

4-Desmethylsterols, 4-methylsterols and triterpene alcohols of eggplant seed oil were isolated and characterized by¹H nuclear magnetic resonance (NMR) and mass spectrometry. In addition to several compounds that have been shown to be present in eggplant seed oil, one triterpene alcohol and three sterols are described for the first time. One of these sterols, 14α-methyl-5α-cholest-9(11)-en-3β-ol, never before had been observed in plant lipids.     

海南西番莲果实香气成分研究

本文应用GC -MS分析了海南西番莲的香气成分 ,乙酸乙酯、丁酸乙酯、3 -羟基丁酸乙酯、己酸乙酯、菠萝呋喃酮、3-羟基己酸乙酯、丁酸异戊酯、丁酸叶醇酯、己酸叶醇酯、异丁酸己酯、己酸己酯、香草酸、2 -己酮、苯甲醛、叶醇、己醇、苄醇、对乙氧基苯甲酸乙酯、十六酸等 1 2 6个成分被检出 ;并对西番莲的果肉、果皮所含香气成分进行了对比。     

Zur elektrochemischen Darstellung des 1,1-Dichlor-4-methylpenta-1,3-diens

Electrochemical Synthesis of 1,1-Dichloro-4-methylpenta-1,3-diene Reaction of 1,1,1-trichloro-4-methylpent-3-en-2-ol ( 2 ) with inorganic acid halides yielded several polychloroalkenes ( 3 – 5 ). These compounds were utilized for the electrochemical synthesis of 1,1-dichloro-4-methylpenta-1,3-diene ( 1 ).     

Barrier properties of poly(lactic acid) and its morphological changes induced by aroma compound sorption

The barrier properties of poly(lactic acid) (PLA) play a key role in food packaging applications. For their optimization, the influence of crystallinity on the barrier properties of PLA and the interaction of PLA with the aroma compound ethyl acetate were investigated. PLA film samples with various crystallinities were fabricated by flat die extrusion and thermocompression and compared to PLA Biophan^?. The degree of crystallinity had no effect on the oxygen permeability. However, an increase of crystallinity caused a decrease in ethyl acetate sorption. The sorption isotherm of ethyl acetate obtained using microgravimetry showed a steep increase with increasing aroma activity, a form which is consistent with a plasticization effect. This behaviour was verified using differential scanning calorimetry and dynamic mechanical analysis. Sorption caused a marked decrease in the glass transition temperature well below room temperature to approximately 0 °C. Furthermore, PLA underwent a solvent‐induced crystallization when equilibrated in ethyl acetate atmosphere at an activity of 0.5. The results obtained show the importance of considering possible interactions between polymer and foodstuff during the optimization step of polymeric materials for food packaging applications. Copyright © 2010 Society of Chemical Industry     

Effect of extraction conditions on sensory quality of virgin olive oil

The extraction conditions of virgin olive oil have a great influence on its sensory quality. During the centrifugation process, temperature and time of malaxing can be altered to potentially affect quality. Malaxing times (15, 30, 45, 60, and 90 min) and temperatures (25 and 35°C) were studied in an experimental oil mill. Volatile compounds, produced through the lipoxygenase pathway (hexanal, Z-3-hexenal, E-2-hexenal, hexyl acetate, Z-3-hexenyl acetate, hexan-1-ol, E-3-hexen-1-ol, Z-3-hexen-1-ol, and E-2-hexen-1-ol), were analyzed by dynamic headspace gas chromatography, gas chromatographymass spectrometry, and gas chromatography-olfactometry. Different amounts of volatiles responsible for positive attributes of green aroma and negative attributes of astringent mouthfeel of virgin olive oil were determined. The results, after applying mathematical procedures, showed that a temperature of 25°C and a malaxing time between 30 and 45 min produced volatile compounds that contribute to the best sensory quality. High temperature (T≥35°C) with minimum values of time (t<30 min) could also be useful as an alternative way to obtain pleasant green virgin olive oils.     

Mandibular gland secretions of the male beewolvesPhilanthus crabroniformis,P. barbatus,andP. pulcher (Hymenoptera: Sphecidae)

The composition of the territorial marking pheromones from mandibular glands of males of the beewolvesPhilanthus crabroniformis, P. barbatus, andP. pulcher have been determined. The structures of the components were elucidated by gas chromatography-mass spectrometry and gas chromatography-Fourier transform infrared spectroscopy. The major compound ofP. crabroniformis is isopropyl tetradecanoate, with somewhat lesser amounts of 2-tridecanone, 3-methyl-3-butenyl tetradecanoate, and 928 (Z)(E)-11-eicosen-1-ol. The major compounds ofP. barbatus are ethyl tetradecanoate and hexadecanal, which are present in approximately a 6040 ratio. These two compounds comprise over 95% of the neutral lipids. Also present in lesser amounts are ethyl dodecanoate, tetradecanal, hexadecan-1-ol, a ^x -octadecen-1-ol, and octadecan-1-ol. The major compounds ofP. pulcher are ethyl (Z)-7-hexadecenoate and geranylgeraniol acetate, which comprise nearly 90% of the neutral lipid fraction, with smaller amounts of tetradecanal, pentadecanal, and ethyl hexadecanoate; trace amounts of ^x hexadecenal, hexadecanal, and octadecanal are also present.     

Photo-oxidation of lipids impregnated on the surface of dried seaweed (<Emphasis Type="Italic">Porphyra yezoensis</Emphasis> Ueda). Characterization of volatiles

Volatiles generated by the photo-oxidation of lipids applied to the surface of dried seaweed (Porphyra yezoensis Ueda) previously exposed to visible light were studied. The surface of dried seaweed was impregnated with eicosapentaenoic acid (EPA) ethyl ester or linoleic acid (LA) methyl ester. The sample was then divided into two parts, and each part was sealed in a 50-mL crimp-top vial with a PTFE silicone-lined cap. One vial was exposed to light from a 100-W tungsten bulb (6000 lux) in an oven at 45°C. The other vial was covered with aluminum foil to shield the seaweed from light and kept in the oven as a control. Volatile compounds in the headspace of the vials were collected by a solid-phase microextraction technique and analyzed by GC-FID and GC-MS. The numbers of peaks as well as the peak areas of volatiles in the light-exposed sample were much greater than those in the control in GC profiles obtained in the same oxidation period. The peak areas of volatiles changed with the prolongation of oxidation time, and the formation rates were different between volatiles. Approximately 28 volatiles were identified in the control kept in the dark as well as in the light-exposed sample impregnated with EPA ethyl ester. The relative amounts of propanal, 2-propenal, 1-penten-3-one, 1-penten-3-ol, 2-butenal, heptanoic acid, and 2-pentenal in the headspace of the light-exposed vials were significantly higher than those in the control, whereas the relative amounts of 3,5-octadien-2-one, ethyl butyrate, and 2,4-heptadienal in the control were significantly higher than those in the headspace of the light-exposed vial. Approximately 35 volatiles were identified from the dried seaweed impregnated with LA methyl ester. The relative amounts of hexanal, 2-heptenal, 2-octenal, octanoic acid methyl ester, and hexanoic acid in the headspace of the light-exposed vial were significantly higher than those in the control, and the relative amounts of 2-decenal, 2,4-nonadienal, and 2,4-decadienal in the control were significantly higher than those in the headspace of the light-exposed vial. We proposed the formation mechanisms of some volatiles to be the well-accepted homolytic-heterolytic cleavage of hydroperoxides that were generated by oxidation of the unsaturated lipids.     

Biphasic homogeneous hydrogenation of sorbic acid with water soluble ruthenium catalysts – aspects of mass transfer

We synthesized a new water soluble ruthenium complex which contains the hydrophilic ligand tris(3-hydroxypropyl)phosphane. This compound catalyzes the regioselective biphasic hydrogenation of sorbic acid to yield 4-hexenoic acid with 82% selectivity and with turnover frequencies of up to 200 h⁻¹. Some thermodynamic and kinetic aspects of this biphasic reaction in water/ethyl acetate were studied.     

Evaluation of fat-derived aroma compounds in blue cheese by dynamic headspace GC/Olfactometry-MS

The aroma compounds in Blue cheese were studied with a dynamic headspace-GC/olfactometry (GC/O-DH) technique and evaluated by both aroma extract dilution analysis (AEDA) and the Osme technique to identify and assign importance to aroma compounds. AEDA aroma dilution values were obtained by sequential reduction of sample size, and Osme values were obtained based on aroma intensity and duration. The most important compounds contributing to Blue cheese aroma were diacetyl, 2-methylpropanal, 3-methylbutanal, ethyl butanoate, ethyl hexanoate, methional, dimethyl trisulfide, 2-heptanone, and 2-nonanone. Compounds central to the characteristic Blue cheese aroma and typically derived from milkfat included 2-heptanone, 2-nonanone, butanoic acid, hexanoic acid, and ethyl esters. Since the methyl ketones contributed the characteristic Blue cheese aroma, a flavor concentrate enriched in methyl ketones to impart characteristic Blue cheese aroma was synthesized using Penicillium roqueforti spores in a model system. A fivefold enhancement in methyl ketone production was obtained by providing aerobic conditions. The addition of sucrose and serine, compounds known to affect mold spore metabolism, did not enhance methyl ketone production but caused generation of an uncharacteristic fruity, floral aroma.     

一种吡嗪酯类香料前体的制备及其热性能

为开发吡嗪酯类香料前体,以2,5-二甲基吡嗪氮氧和丙烯酸噻吩甲酯为原料,在醋酸钯的催化下经偶联反应,合成3-(3,6-二甲基-吡嗪氮氧-2-基)丙烯酸噻吩甲酯目标化合物,通过1H NMR、13C NMR、IR、HRMS表征其结构,并采用热重-微分热重（TG-DTG）和热裂解-气相色谱/质谱法（Py-GC/MS）测其热性能。结果表明：目标化合物从170 oC开始降解,主要热失重区间为170 oC~875 oC,在257 oC失重速率最大,总失重为76.5%。在300 oC~900 oC的有氧和无氧裂解氛围下,共鉴定出11种挥发性产物,主要有烷基吡嗪类、2-甲基噻吩、2-噻吩甲醇等特征香味物质,有氧氛围下热裂解产物种类较多,相对含量较高。依据主要裂解产物的种类及相对含量的变化,初步揭示了裂解机理。目标化合物在单料烟中的最适宜添加量为2 mg/kg。