Quantification of phenolic compounds in vegetable oils by mixed-mode solid-phase extraction isotope chemical labeling coupled with UHPLC-MS/MS.

In the present work, a rapid, accurate and cost-effective method has been developed for the simultaneous quantification of phenolic compounds in oil using mixed-mode solid-phase extraction (SPE) coupled with chemical labeling UHPLC-MS/MS. Mix-mode SPE weak cation cartridges were selected to enrich and purify phenolic compounds in oil, and hydroxyl moiety was dansylation as stable-isotope internal standard. The major parameters that affected the extraction and chemical labeling efficiency were investigated, and the method was fully validated. The limit of quantifications and the limit of detections were 0.002 µg kg-1 ~ 0.10 µg kg-1 and 0.006 µg kg-1 ~ 0.30 µg kg-1, respectively. The recoveries were 61.2% ~ 129.3% with intra-day and inter-day precision less than 12%. The results for 38 rapeseed oils revealed that 14 phenolic compounds, including canolol, phenolic acids, phenolic alcohols, tyrosol and vanillin from trace levels to relatively high content.

Volatilome fingerprint of red wines aged with chips or staves: Influence of the aging time and toasting degree.

The influence on aroma compounds chips or staves and toasting degree have been analyzed in red wines aged for two periods of time. Ethyl propanoate, ethyl butanoate, ethyl octanoate, ethyl acetate, isoamyl acetate, isobutanol, 2-methyl-1-butanol, 2-phenylethanol, E-2-hexenol, octanal, nonanal, decanal, γ-nonalactone, furfural, 5-methylfurfural, 2-methoxy-4-vinylphenol and cis-whiskey lactone were the compounds that contribute the most to the aroma series profile. By means of principal components analysis, esters were related to the aging time; cis-whiskey lactone with the type of wood pieces and octanal, 5-methyl furfural and cis-whiskey lactone with the toasting degree. Star plot show that woody aroma compounds are dominant in wines aged with low toasting degree oak pieces, whereas medium plus toasted pieces increased the concentration of aroma compounds with fruity aroma descriptors. Wines with prominent fruity or woody aromas can be obtained depending upon the degree of toasting of wood pieces used for aging.

DISCOVER: A facile structure-based screening method for vinyl compound producing microbes.

Here we report a novel structure-based microbial screening method for vinyl compound discovery, DISCOVER (direct screening method based on coupling reactions for vinyl compound producers). Through a two-step screening procedure based on selective coupling reactions of terminal alkenes, the thiol-ene reaction (1st step of screening) and Mizoroki-Heck reaction, followed by iodine test (2nd step of screening), microbes producing vinyl compounds like itaconic acid (IA) can be isolated from soil samples. In the 1st step of screening, soil sources are plated on agar medium supplemented with an antimicrobial agent, α-thioglycerol (TG), and a radical initiator, VA-044 (VA). In the 2nd step of screening, vinyl compounds produced in the cultures are labelled with iodobenzene via the Mizoroki-Heck reaction, followed by an iodine test, leading to the detection and characterisation of labelled products. We evaluated the validity of DISCOVER using IA and its producer Aspergillus terreus. Experimental data supported our hypothesis that IA reacts with TG in the medium via the thiol-ene reaction and consequently, A. terreus rapidly forms colonies on the agar medium because of the loss of the antimicrobial activity of TG. Using DISCOVER, high throughput and selective isolation of A. terreus strains producing IA was possible from soils.

Simultaneous Determination of Furan and Vinyl Acetate in Vapor Phase of Mainstream Cigarette Smoke by GC-MS.

A simple and sensitive method for simultaneous determination of furan and vinyl acetate (VA) in vapor phase of mainstream cigarette smoke with cold trap and gas chromatography-mass spectrometry (GC-MS) was developed. A Cambridge filter pad (CFP) was placed in front of the impingers of smoking machine to remove the particle phase from cigarette smoke. Furan and VA in vapor phase of mainstream cigarette smoke were collected in two impingers connected in series by filled with methanol at -78°C. The solutions were added with deuterium-labeled furan-d4 and VA-d6 as internal standards and analyzed by GC-MS. The results showed that the calibration curves for furan and VA were linear (r2 > 0.9995) over the studied concentration range. The intra- and inter-day precision values for furan and VA were <7.07% and <9.62%, respectively. The extraction recoveries of furan and VA were in the range of 94.5-97.7% and 92.3-94.9%, respectively. Moreover, the limits of detection for furan and VA were 0.028 µg mL-1 and 1.3 ng mL-1, respectively. The validated method has been successfully applied to determine the emissions of furan and VA in the vapor phase of mainstream cigarette smoke under International Organization for Standardization (ISO) and Canadian Intense (CI) smoking regimen.

Simultaneous Determination of Furan and Vinyl Acetate in Vapor Phase of Mainstream Cigarette Smoke by GC-MS

ABSTRACT A simple and sensitive method for simultaneous determination of furan and vinyl acetate (VA) in vapor phase of mainstream cigarette smoke with cold trap and gas chromatography-mass spectrometry (GC-MS) was developed. A Cambridge filter pad (CFP) was placed in front of the impingers of smoking machine to remove the particle phase from cigarette smoke. Furan and VA in vapor phase of mainstream cigarette smoke were collected in two impingers connected in series by filled with methanol at -78°C. The solutions were added with deuterium-labeled furan-d4 and VA-d6 as internal standards and analyzed by GC-MS. The results showed that the calibration curves for furan and VA were linear (r2 > 0.9995) over the studied concentration range. The intra- and inter-day precision values for furan and VA were <7.07% and <9.62%, respectively. The extraction recoveries of furan and VA were in the range of 94.5-97.7% and 92.3-94.9%, respectively. Moreover, the limits of detection for furan and VA were 0.028 µg mL-1 and 1.3 ng mL-1, respectively. The validated method has been successfully applied to determine the emissions of furan and VA in the vapor phase of mainstream cigarette smoke under International Organization for Standardization (ISO) and Canadian Intense (CI) smoking regimen.

Cold-pressed and hot-pressed rapeseed oil: The effects of roasting and seed moisture on the antioxi- dant activity, canolol, and tocopherol level.

BACKGROUND: The paper looks at the levels of canolol, tocopherols and antioxidant activity in cold-pressed and hot-pressed rapeseed oils produced from seeds of various moisture levels (5%, 7.5%, and 10%). The paper also considers the effects of seed roasting on the levels of these compounds. METHODS: The material used for the tests was rapeseed cv. Adrianna. The quality of the oils obtained is determined using peroxide and acid values. The levels of canolol and tocopherols are analyzed using HPLC. The DPPH radical-scavenging activity method for oil samples and phenolic extract from oils was used. RESULTS: It has been demonstrated that the oils produced from rapeseeds with a 5% moisture content, and   in particular from cold-pressed oils, were characterized by the lowest peroxide values. Cold-pressed oils produced from rapeseeds with a 5% moisture content were characterized by higher levels of tocopherols and plastochromanol-8. In the case of hot-pressed oils, the highest levels of tocopherols were found in oils pro- duced from seeds with a 7.5% moisture content, and the greatest amount of PC-8 (more than 4 mg/100 g) was found in oils produced from seeds with a 10% moisture content. Hot-pressed oils have been shown to have higher levels of these compounds than cold-pressed oils. Both roasting and hot pressing led to an increase in the amount of canolol in the oils investigated. When analysing the antioxidant activity of the oils and phenolic extracts it was shown that phenolic compounds are responsible for approx. 10% of total antioxidant activity. CONCLUSIONS: Various levels of biologically active compounds were shown to be present in the rapeseed oil obtained from raw materials of a varying moisture content. The type of pressing process (cold-pressing or hot-pressing) and whether the seeds have undergone roasting has also been shown to affect the resulting oil and the level of native antioxidants it contains.

Autolysis of Aspergillus oryzae Mycelium and Effect on Volatile Flavor Compounds of Soy Sauce.

The autolyzed mycelia of Aspergillus oryzae are rich in proteins, nucleic acids, sugar, and other biomacromolecules, and are one of the main contributors to the flavor profile of commercially important fermented goods, including soy sauce and miso. We induced autolysis of the mycelia of A. oryzae over 1 to 10 d, and found that the maximum dissolved amounts of total protein and nucleic acid ratio accounted for 28.63% and 88.93%, respectively. The organic acid content, such as citric acid, tartaric acid, succinic acid, lactic acid, and acetic acid, initially increased and then decreased as autolysis progressed, corresponding to changes in pH levels. The main characteristic flavor compounds in soy sauce, namely, ethanol, 2-phenylethanol, and 2-methoxy-4-vinylphenol, were all detected in the autolysate. Subsequently, we tested the effect of adding mycelia of A. oryzae during the fermentation process of soy sauce for 60 d, and found that addition of 1.2‰ A. oryzae mycelia provided the richest flavor. Overall, our findings suggest that compounds found in the autolysate of A. oryzae may promote the flavor compounds of soy sauce, such as alcohols, aldehydes, phenols, and esters.

Studies on the Simultaneous Formation of Aroma-Active and Toxicologically Relevant Vinyl Aromatics from Free Phenolic Acids during Wheat Beer Brewing.

During the brewing process of wheat beer, the desired aroma-active vinyl aromatics 2-methoxy-4-vinylphenol and 4-vinylphenol as well as the undesired and toxicologically relevant styrene are formed from their respective precursors, free ferulic acid, p-coumaric acid, and cinnamic acid, deriving from the malts. Analysis of eight commercial wheat beers revealed high concentrations of 2-methoxy-4-vinylphenol and 4-vinylphenol always in parallel with high concentrations of styrene or low concentrations of the odorants in parallel with low styrene concentrations, suggesting a similar pathway. To better understand the formation of these vinyl aromatics, each process step of wheat beer brewing and the use of different strains of Saccharomyces cerevisiae were evaluated. During wort boiling, only a moderate decarboxylation of free phenolic acids and formation of desired and undesired vinyl aromatics were monitored due to the thermal treatment. In contrast, this reaction mainly occurred enzymatically catalyzed during fermentation with S. cerevisiae strain W68 with normal Pof(+) activity (phenolic off-flavor) resulting in a wheat beer eliciting the typical aroma requested by consumers due to high concentrations of 2-methoxy-4-vinylphenol (1790 µg/L) and 4-vinylphenol (937 µg/L). Unfortunately, also a high concentration of undesired styrene (28.3 µg/L) was observed. Using a special S. cerevisiae strain without Pof(+) activity resulted in a significant styrene reduction (

The effect of thermodynamic properties of solvent mixtures explains the difference between methanol and ethanol in C.antarctica lipase B catalyzed alcoholysis.

Kinetic modelling, molecular modelling, and experimental determination of the initial reaction velocity of lipase-catalyzed alcoholysis were combined to study the effect of the alcohol substrate to catalytic activity. The model system consisted of methanol or ethanol at varying concentrations, vinyl acetate as ester substrate 15.2% (v/v), toluene as organic solvent, water at a controlled thermodynamic activity of 0.09, and C. antarctica lipase B as enzyme. For both alcohol substrates, the initial reaction velocity increased sharply at low concentrations and reached a maximum at 0.7% (v/v) for methanol and 2% (v/v) for ethanol. For higher concentrations, the reaction rate decreased to a level of 74% and 60% of the peak value, respectively, due to substrate inhibition. The concentration dependency was described by a kinetic model, including a ping-pong bi-bi mechanism and competitive inhibition by the alcohol, and confirmed previous observations that methanol is more efficiently inhibiting the enzyme than ethanol. However, if the initial reaction velocity was expressed in terms of thermodynamic activity of the two alcohol substrates, the maximum of initial reaction velocity was similar for methanol (a MeOH(max)=0.19) and ethanol (a EtOH(max)=0.21). This was confirmed by molecular modelling which resulted in similar KM (0.22 and 0.19) and Ki values (0.44 and 0.49) for methanol and ethanol, respectively, if expressed in thermodynamic activities. Thus, the experimentally observed difference between methanol and ethanol is not due to differences in interaction with the enzyme but is a consequence of the thermodynamics of the substrate-solvent mixture. For low concentrations in toluene, the activity coefficient of methanol is 40% higher than the activity coefficient of ethanol (γ MeOH=8.5, γ EtOH=6.1).

Oxylipins in the spikemoss Selaginella martensii: Detection of divinyl ethers, 12-oxophytodienoic acid and related cyclopentenones.

Green tissues of spikemoss Selaginella martensii Spring possessed the complex oxylipins patterns. Major oxylipins were the products of linoleic and α-linolenic acids metabolism via the sequential action of 13-lipoxygenase and divinyl ether synthase (DES) or allene oxide synthase (AOS). AOS products were represented by 12-oxophytodienoic acid (12-oxo-PDA) isomers. Exceptionally, S. martensii possesses high level of 12-oxo-9(13),15-PDA, which is very uncommon in flowering plants. Separate divinyl ethers were purified after micro-preparative incubations of linoleic or α-linolenic acids with homogenate of S. martensii aerial parts. The NMR data allowed us to identify all geometric isomers of divinyl ethers. Linoleic acid was converted to divinyl ethers etheroleic acid, (11Z)-etheroleic acid and a minority of (ω5Z)-etheroleic acid. With α-linolenate precursor, the specificity of divinyl ether biosynthesis was distinct. Etherolenic and (ω5Z)-etherolenic acids were the prevailing products while (11Z)-etherolenic acid was a minor one. Divinyl ethers are detected first time in non-flowering land plant. These are the first observations of fatty acid metabolism through the lipoxygenase pathway in spikemosses (Lycopodiophyta).

Gold-catalyzed selective oxidation of 4-oxahepta-1,6-diynes to 2H-pyran-3(6H)-ones and chromen-3(4H)-ones via ß-gold vinyl cation intermediates.

α-Oxo gold carbenes generated in situ via the gold-catalyzed selective oxidation of 4-oxahepta-1,6-diynes were effectively trapped by internal alkynes, resulting in the formation of 2H-pyran-3(6H)-ones, , and chromen-3(4H)-ones, , upon facile trapping the vinyl cation intermediates by an external N-oxide and internal aryl ring system.

Approaches of aroma extraction dilution analysis (AEDA) for headspace solid phase microextraction and gas chromatography-olfactometry (HS-SPME-GC-O): Altering sample amount, diluting the sample or adjusting split ratio?

Aroma extract dilution analysis (AEDA) is widely used for the screening of aroma-active compounds in gas chromatography-olfactometry (GC-O). In this study, three aroma dilution methods, (I) using different test sample volumes, (II) diluting samples, and (III) adjusting the GC injector split ratio, were compared for the analysis of volatiles by using HS-SPME-AEDA. Results showed that adjusting the GC injector split ratio (III) was the most desirable approach, based on the linearity relationships between Ln (normalised peak area) and Ln (normalised flavour dilution factors). Thereafter this dilution method was applied in the analysis of aroma-active compounds in Japanese soy sauce and 36 key odorants were found in this study. The most intense aroma-active components in Japanese soy sauce were: ethyl 2-methylpropanoate, ethyl 2-methylbutanoate, ethyl 3-methylbutanoate, ethyl 4-methylpentanoate, 3-(methylthio)propanal, 1-octen-3-ol, 2-methoxyphenol, 4-ethyl-2-methoxyphenol, 2-methoxy-4-vinylphenol, 2-phenylethanol, and 4-hydroxy-5-ethyl-2-methyl-3(2H)-furanone.

Multidimensional mass spectrometry-based shotgun lipidomics analysis of vinyl ether diglycerides.

Diglycerides play a central role in lipid metabolism and signaling in mammalian cells. Although diacylglycerol molecular species comprise the majority of cellular diglycerides that are commonly measured using a variety of approaches, identification of extremely low abundance vinyl ether diglycerides has remained challenging. In this work, representative molecular species from the three diglyceride subclasses (diacyl, vinyl ether, and alkyl ether diglycerides; hereafter referred to as diradylglycerols) were interrogated by mass spectrometric analysis. Product ion mass spectra of the synthesized diradylglycerols with varied chain lengths and degrees of unsaturation demonstrated diagnostic fragmentation patterns indicative of each subclass. Multidimensional mass spectrometry-based shotgun lipidomics (MDMS-SL) analysis of mouse brain and heart lipid extracts were performed using the identified informative signature product ions. Through an array of tandem mass spectrometric analyses utilizing the orthogonal characteristics of neutral loss scanning and precursor ion scanning, the differential fragmentation of each subclass was exploited for high-yield structural analyses. Although molecular ion mass spectra readily identified diacylglycerol molecular species directly from the hexane fractions of tissue extracts enriched in nonpolar lipids, molecular ion peaks corresponding to ether-linked diglycerides were not observable. The power of MDMS-SL utilizing the tandem mass spectrometric array analysis was demonstrated by identification and profiling of individual molecular species of vinyl ether diglycerides in mouse brain and heart from their undetectable molecular ion peaks during MS(1) analysis. Collectively, this technology enabled the identification and profiling of previously inaccessible vinyl ether diglyceride molecular species in mammalian tissues directly from extracts of biologic tissues.

Vinyl flooring in the home is associated with children's airborne butylbenzyl phthalate and urinary metabolite concentrations.

Prior studies have shown that vinyl flooring as well as the vinyl-softening plasticizers butylbenzyl phthalate (BBzP) and di(2-ethylhexyl) phthalate (DEHP) are associated with asthma and airway inflammation. Although DEHP exposure is primarily dietary, whether home vinyl flooring contributes to indoor air and urinary metabolite concentrations for these two phthalates is unclear. Exposures to BBzP and DEHP were examined in a prospective birth cohort of New York City children (n=239) using: (i) visual observation of potential phthalate containing flooring, (ii) a 2-week home indoor air sample, and (iii) concurrent urinary metabolites in a subset (n=193). The category "vinyl or linoleum" flooring was observed in 135 (56%) of monitored rooms; these rooms had statistically significantly higher indoor air geometric mean concentrations of BBzP (23.9 ng/m(3)) than rooms with wood or carpet flooring (10.6 ng/m(3)). Children from homes with "vinyl or linoleum" flooring also had significantly higher urinary BBzP metabolite concentrations than other children. Indoor air BBzP and urinary metabolite concentrations were correlated positively (Spearman's rho 0.40). By contrast, indoor air DEHP was not associated with flooring type nor with its urinary metabolite concentrations. Vinyl flooring in the home may be an important source of children's exposure to BBzP via indoor air.

Development and characterization of poly(1-vinylpyrrolidone-co-vinyl acetate) copolymer based polymer electrolytes.

Gel polymer electrolytes (GPEs) are developed using poly(1-vinylpyrrolidone-co-vinyl acetate) [P(VP-co-VAc)] as the host polymer, lithium bis(trifluoromethane) sulfonimide [LiTFSI] as the lithium salt and ionic liquid, and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide [EMImTFSI] by using solution casting technique. The effect of ionic liquid on ionic conductivity is studied and the optimum ionic conductivity at room temperature is found to be 2.14 × 10(-6) S cm(-1) for sample containing 25 wt% of EMImTFSI. The temperature dependence of ionic conductivity from 303 K to 353 K exhibits Arrhenius plot behaviour. The thermal stability of the polymer electrolyte system is studied by using thermogravimetric analysis (TGA) while the structural and morphological properties of the polymer electrolyte is studied by using Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction analysis (XRD), respectively.

Active matrix-based collection of airborne analytes: an analyte recording chip providing exposure history and finger print.

In the field of sensors that target the detection of airborne analytes, Corona/lens-based-collection provides a new path to achieve a high sensitivity. An active-matrix-based analyte collection approach referred to as "airborne analyte memory chip/recorder" is demonstrated, which takes and stores airborne analytes in a matrix to provide an exposure history for off-site analysis.

Nutrient digestibility and growth performance of pigs fed diets with different levels of canola meal from Brassica napus black and Brassica juncea yellow.

Nutrient digestibility and the effect of high dietary inclusion of canola meals from Brassica napus black (BNB) and Brassica juncea yellow (BJY) on growing and weaned pigs performance were determined. In Exp.1, 6 ileal cannulated barrows (initial BW = 20.7 ± 1.5 kg) were used to determine the apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of AA in BNB and BJY. Pigs were allotted to diets containing either BNB or BJY as the sole source of protein in a crossover design to give 6 replicates per diet. The SID of all AA in BNB and BJY were similar. In Exp. 2, 168 weaned pigs (initial BW = 7.61 ± 0.76 kg) were assigned in a randomized complete block design to 7 diets (n = 24) consisting of a wheat-soybean meal-based control diet and 6 diets containing 5, 10 or 15% of canola meal derived from either BNB or BJY to determine the effect of different dietary inclusion on growth performance over a 28-d period postweaning. Diets were formulated to contain similar NE and SID of Lys. There were no differences in growth performance among treatments. In Exp. 3, 162 weaned pigs (initial BW = 7.26 ± 0.70 kg) were used to determine the effect of high BNB and BJY inclusion level without or with multicarbohydrase supplementation on growth performance and apparent total tract digestibility (ATTD) of CP, DM, and GE. A wheat-soybean meal-based control diet and 8 diets containing 20 and 25% of either BNB or BJY without or with added multi-carbohydrase were formulated (n = 18) to contain comparable NE and similar SID of Lys contents. Feeding the diets containing 25% of BNB or BJY supported similar growth performance as those containing 20%. The multi-carbohydrase had no effect on growth performance but improved (P < 0.05) the ATTD of DM, CP, and GE compared with those fed nonsupplemented diets irrespective of canola meal type. Diets containing 25% canola meal had lower (P < 0.05) ATTD of DM, CP, and GE regardless of canola meal type compared with the 20% canola meal diets. There was an interaction (P < 0.05) between canola meal type and inclusion level on ATTD of DM in which ATTD of DM decreased with increasing inclusion of both canola meal types. Results of the current study indicate that both BNB and BJY can be included up to 25% in weaned pig diets without compromising performance as long as the diets are formulated on an NE and SID of Lys basis. Also, enzyme addition improved the ATTD of CP, DM, and GE in weaned pigs in both BNB and BJY diets.

Effect of seed roasting on canolol, tocopherol, and phospholipid contents, Maillard type reactions, and oxidative stability of mustard and rapeseed oils.

This work was carried out to study the effect of roasting on different compositional parameters and oil oxidative stability of three Brassica species (Brassica juncea (BJ), B. juncea var. oriental (BJO), and Brassica napus (rapeseed, RS)). After 10 min of roasting at 165 °C, canolol contents of BJ, BJO, and RS oil reached 297.8, 171.6, and 808.5 µg/g, and the phospholipid phosphorus contents reached 453.6, 342.6, and 224.2 µg/g oil, respectively. The BJ and BJO seeds showed more prominent browning reactions than RS, due to the presence of higher amounts of reducing sugars, lysine, arginine and the occurrence of Maillard type browning reactions of phospholipids. The UV-visible spectra, fluorescence, and pyrrole content showed the presence of browning reaction products in the roasted seed oils. Roasting increased the oxidative stability of all varieties. Canolol formation could only partially explain such observations. Other roasting effects such as phospholipid extraction and Maillard type browning reaction products were also responsible for the increased stability.

Improved method for measuring and characterizing phthalate emissions from building materials and its application to exposure assessment.

Phthalate emission from vinyl floorings was measured in specially designed stainless steel chambers. Phthalate concentrations increased and reached steady state after 2 to 5 days for all experiments. By having a high ratio of emission surface to sorption surface, avoiding mass loss of phthalates onto sampling pathways, and improving air mixing inside the chamber, the time to reach steady state was significantly reduced, compared to previous studies (1 to 5 months). An innovative approach was developed to determine y0, the gas-phase concentration of phthalates in equilibrium with the material phase, which is the key parameter controlling phthalate emissions. Target phthalate material-phase concentration (C0) and vapor pressure (Vp) were explicitly measured and found to have great influences on the y0 value. For low phthalate concentrations in materials, a simple partitioning mechanism may linearly relate y0 and C0, but cannot be evoked for high-weight phthalate percentages. In addition, the sorption kinetics and adsorption isotherm of phthalates on stainless steel chamber surfaces were determined experimentally. Independently measured or calculated parameters were used to validate a semivolatile organic compounds (SVOCs) emission model, with excellent agreement between model predictions and the observed chamber concentrations in gas and stainless steel phases. With the knowledge of y0 and emission mechanisms, human exposure to phthalates from tested floorings was assessed; the levels were comparable to previous studies. This work developed a rapid, novel method to measure phthalate emissions; emission measurement results can be connected to exposure assessment and help health professionals estimate screening-level exposures associated with SVOCs and conduct risk-based prioritization for SVOC chemicals of concern.

Aroma-active components of yeast extract pastes with a basic and characteristic meaty flavour.

BACKGROUND: Aroma-active compounds, together with sugars, amino acids, fat and nucleotides, are the main chemical species determining the characteristic aroma and taste of food. For selecting yeast extract pastes products with a less undesirable aroma, the aroma-active compounds that affect the overall consumer acceptance of yeast extract pastes products were analysed in this work. RESULTS: The aroma-active compounds of yeast extract pastes were extracted by using dynamic headspace extraction or simultaneous distillation extraction, and were detected by gas chromatography-olfactrometry-mass spectrometry in conjunction with dynamic headspace dilution analysis or aroma extract dilution analysis. Sensory results revealed that a meaty, roasted aroma was the dominant of overall aroma. The important aroma-active compounds referred in this work were mainly aldehydes, acids, ketones, furan derivatives, pyrazines, and sulfur-containing compounds. Of these, six volatile compounds such as 3-methylbutanal, 2,3-butanedione, 2,3,5-trimethyl-pyrazin, acetic acid ethenyl ester, 2-acetyl-1-pyrroline and (E,E)-2,4-decadienal had never been reported before as key aroma-active compounds of yeast extract pastes. CONCLUSIONS: The key aroma-active compounds were identified in basic and characteristic meaty flavour yeast extract pastes, and their characterisation was determined.