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PubMed2004

Potential of SPME-GC and chemometrics to detect adulteration of soft fruit purées.

The potential of combining solid-phase microextraction (SPME) with gas chromatography and chemometric data analysis to differentiate between pure strawberry samples (Fragraria ananassa) and strawberry samples adulterated with 10, 40, and 70% (v/v) apple purée was investigated. The method involved the extraction of aroma volatiles from the headspace of the purée samples using a SPME fiber followed by GC analysis with flame ionization detection. The principal component analysis (PCA) data matrix consisted of the relative percent peak areas of 37 compounds deemed to be significant in the differentiation of the samples on the basis of adulteration. The PCA results clearly showed that differentiation of the adulterated and unadulterated samples was possible, particularly at the higher levels of adulteration. Partial least-squares regression (PLSR) using a dummy set of Y variables (set to 0 for unadulterated and 1 for adulterated samples) resulted in clear discrimination between unadulterated purées and those containing 40 and 70% (v/v) apple. PLSR using a second set of Y variables, consisting of the actual level of adulteration, enabled quantification of apple purée with a standard error of prediction of 11.6%, implying a minimum detectable level of 25% (v/v) apple. GC-MS analysis enabled identification of the compounds with the greatest influence on sample differentiation. These compounds were identified as hexanoic acid, 2-hexenal, and alpha-farnesene, all of which are key aroma compounds in apples.

Chromatography, Gas↗

PubMed2004

Metabolites of lesser grain borer in grains.

Many volatile alcohol and ester metabolites of the lesser grain borer (LGB, Rhyzopertha dominica) cultured on wheat grain were identified. Volatiles from infested samples at 80 degrees C were collected on Tenax absorbent, thermally desorbed, and analyzed by gas chromatography (GC) using infrared (IR) and mass (MS) detectors for component identification. A solid-phase microextraction (SPME) technique was used to analyze selected samples with a GC-MS system set up for obtaining chemical ionization mass spectra. SPME was also used in a synthesis process required to identify ester metabolites. Predominant compounds in LGB-infested grains were 2-pentanol and its esters of 2-methyl-2-pentenoic (A) and 2,4-dimethyl-2-pentenoic (B) acids, which are known aggregation pheromones, dominicalures 1 and 2. 2-Pentanol esters of saturated A, beta-keto- and beta-hydroxy derivatives of A and B, homologues of A and B, and acid moieties lacking the 2-methyl substitution were found. Other straight- and branched-chain secondary alcohols and their esters were also observed. Reexamination of GC-MS-IR data acquired in previous investigations of LGB cultured on sorghum grain and commercial samples in a grain odor study showed the presence of many LGB metabolites in addition to the known dominicalures.

Animals↗

PubMed2004

Representativeness of extracts of offset paper packaging and analysis of the main odor-active compounds.

Packagings often carry odors due to the support and printing inks. The aim of the investigation was to define a representative solvent-free extract of paper-based packaging materials printed by the offset process, for the identification of the odor-causing volatile compounds. Static headspace and solid-phase microextraction were the two applied extraction methods. Representativeness tests showed that the odor of the PDMS fiber extract gave satisfying odor similarities with the original packaging. The sample incubation was performed at 40 degrees C for 30 min, whereas the extraction time was 3 min at 40 degrees C. Extracts of both the nonprinted and printed papers of different batches were analyzed by gas chromatography-olfactometry. 4-Phenylcyclohexene was identified as the most potent compound contributing to the latex-like odor of the nonprinted paper. Among the 13 major odorants identified by mass spectrometry, 10 were aldehydes and ketones generated by oxidation of the printing ink resins. The ratio of odorants to interferences was too low for a possible detection of the key odorants by nonseparative techniques such as sensor arrays.

Aldehydes↗

PubMed2004

The effects of sample preparation and gas chromatograph injection techniques on the accuracy of measuring guaiacol, 4-methylguaiacol and other volatile oak compounds in oak extracts by stable isotope dilution analyses.

The deuterium-labeled standards [(2)H(3)]-guaiacol and [(2)H(3)]-4-methylguaiacol were synthesized and utilized in a method employing gas chromatography-mass spectrometry to determine the concentration of guaiacol and 4-methylguaiacol in wine or extracts of oak shavings. The method was combined with previously published methods for 4-ethylphenol, 4-ethylguaiacol, cis- and trans-oak lactone and vanillin, so that all these compounds could be quantified in a single analysis. The method can employ either liquid-liquid extraction or headspace solid-phase microextraction (SPME) and is rapid, robust, precise, and accurate. Under certain conditions, there was artifactual generation, to varying degrees, of guaiacol, 4-methylguaiacol, cis-oak lactone, and vanillin during the analysis of oak extracts, especially when diethyl ether extraction and injector block temperatures at or above 225 degrees C were employed. The most substantial effects were observed for guaiacol, in which results could be exaggerated by over 10 times. These artifacts could be avoided by using headspace SPME or by preparing liquid-liquid extracts with pentane or pentane/diethyl ether (2:1) injected at 200 degrees C providing spot checks using headspace SPME were performed. Data obtained for previously published quantitative determination of guaiacol in oak extracts should be reexamined carefully, with special attention paid to their respective methods of sample preparation and analysis.

Chromatography, Gas↗

PubMed2004

Relationship between procyanidin and flavor contents of cocoa liquors from different origins.

The flavor of eight cocoa liquors of different origins (Africa, America, and Asia) and different varieties (Fine grades: criollo, trinitario, and nacional. Bulk-basic grade: forastero.) was analyzed by headspace solid-phase microextraction mass spectrometry (HS-SPME-MS). Their procyanidin contents were quantified by HPLC-UV (280 nm). Fine varieties with short fermentation processes proved to contain more procyanidins, while criollo from New Guinea and forastero beans showed the highest aroma levels. The levels of cocoa aroma compounds formed during roasting are shown to vary directly with bean fermentation time and inversely with residual procyanidin content in cocoa liquor. Measurement of antioxidant activity in cocoa liquor proved to be a useful tool for assessing residual polyphenols.

Africa↗

PubMed2004

Aroma evaluation of an aquatic herb, Changpo (Acorus calamus Var. angustatus Bess), by AEDA and SPME.

This study was conducted to determine the volatile flavor composition of fresh changpo (Acorus calamus var. angustatus Bess) leaves quantitatively and qualitatively by use of two internal standards and to determine which volatile compounds are primarily responsible for the aroma of this aquatic herb. The headspace composition of fresh changpo leaves was also analyzed by a solid-phase microextraction method. Aroma extract dilution analysis (AEDA) and sniffing test by gas chromatography-olfactometry were used for the detection of aroma-active compounds of this herb. According to the instrumental analyses of the changpo oil, octanoic acid (49.13%), alpha-cedrene (16.71%), alpha-phellandrene (4.46%), and gamma-elemene (3.75%) were the most abundant compounds. n-Butylidene dihydrophthalide (8.61%), trans,trans-farnesyl acetate (7.29%), and trans-2-dodecenal (7%) were the main components of changpo headspace. cis-beta-Farnesene was evaluated as the key aroma compound of this herb from results of AEDA and sniffing test.

Acorus↗

PubMed2005

Interaction of soluble peptides and proteins from skeletal muscle with volatile compounds in model systems as affected by curing agents.

The effect of curing agents (salt, glucose, nitrate, nitrite, and ascorbic acid) on the binding of skeletal peptides (carnosine and anserine) and a sarcoplasmic protein (myoglobin) with key flavor compounds (hexanal, octanal, 2-pentanone, 2-methylbutanal, and 3-methylbutanal) has been studied by solid-phase microextraction (SPME). Curing agents had an effect on the interaction process between carnosine and volatile compounds, which was higher than the interactions observed with anserine and myoglobin. Sodium chloride decreased the interaction of volatiles with carnosine except for octanal, which was increased, and 2-pentanone, which was unaltered. Ascorbic acid exerted the highest effect by decreasing the interaction of carnosine with all of the volatile compounds except for octanal and 2-pentanone. The interaction with anserine was affected by sodium chloride, nitrate, and nitrite, producing a decrease in the interaction with hexanal, octanal, and methional. Finally, sodium chloride, glucose, and nitrite increased the interaction of myoglobin with hexanal, octanal, and methional. The effect of simulated stages of the curing process on the binding was also studied. A combined effect of the curing agents resulted in a change in the relative proportions of volatile compounds that can lead to different flavor perceptions of dry-cured meat products.

Anserine↗

PubMed2004

Analysis of virgin olive oil volatiles by a novel electronic nose based on a miniaturized SAW sensor array coupled with SPME enhanced headspace enrichment.

A novel electronic nose based on solid-phase microextraction (SPME) coupled with a surface acoustic wave (SAW) sensor array has been used to analyze different quality virgin olive oils. A mathematical model was designed with 37 samples to distinguish lampante from the other virgin olive oils categories (extra-virgin and virgin), because lampante-virgin olive oils cannot be consumed without a previous refining process. The model, successfully validated with a test set of 16 samples, was able to classify 90% of the samples correctly. Misclassifications were explained by SPME-HRGC analyses and a second sensory evaluation.

Acoustics↗

PubMed2005

Study of both sunflower oil and its headspace throughout the oxidation process. Occurrence in the headspace of toxic oxygenated aldehydes.

The static headspace composition of sunflower oil throughout the oxidation process at 70 degrees C with circulating air is studied by means of solid-phase microextraction followed by gas chromatography-mass spectrometry (SPME-GC-MS); at the same time the liquid phase of the same oil is studied by means of Fourier transform infrared (FTIR) spectroscopy. Each technique provides complementary information about the process; FITR spectroscopy detects changes in the functional groups of the liquid matrix in a global way and SPME/GC-MS provides information about the different components present in the volatile phase during the oxidation process. Concordance between the timing of the changes produced in both liquid and gaseous phases is observed, as well as agreement and complementarity in the results obtained from both phases. The formation of some well-known genotoxic and cytotoxic oxygenated aldehydes in this process and their presence in the oil headspace are proved.

Aldehydes↗

PubMed2004

Fast screening method for volatile compounds of oak wood used for aging wines by headspace SPME-GC-MS (SIM).

A headspace solid-phase microextraction (HS-SPME) method is proposed for analyzing the main volatile components from a sensory standpoint (furfural, oak lactones, eugenol, vanillin, and syringaldehyde) present in nontoasted and toasted oak wood of different origins. To maximize the yield of compounds extracted from wood chips and to obtain a good precision of the method, the most important variables affecting HS-SPME have been studied. The best results were obtained when the sample was heated at 70 degrees C and the headspace extracted for 40 min with a DVB/CAR/PDMS fiber, which gave the overall best recovery. The values for the repeatability ranged from 6.4 to 7.8%, and those for the reproducibility from 5.4 to 8.7%. The precision of the results obtained makes the proposed technique appropriate for its use in characterizing oak wood samples of different origins and in the selection of the most suitable oak wood to age wines and spirits, on the basis of the chemical composition of the wood samples.

Food Handling↗

PubMed2004

Comparison of strategies for extraction of high molecular weight polycyclic aromatic hydrocarbons from drinking waters.

Simple, rapid, and inexpensive methods have been developed for the determination of polycyclic aromatic hydrocarbons (PAHs) in drinking waters without interferences from other chemical contaminants by use of two different extraction techniques and analysis by an optimized reverse-phase (RP) high-performance liquid chromatography followed by fluorescence detection (HPLC-FLD) method. The feasibility of SPE (solid-phase extraction) and SPME (solid-phase microextraction) for the determination of PAH in drinking water samples has been evaluated. Several parameters have been studied and optimized for both extraction procedures. The relationship between the nature of the fibers and the quantity of extracted compounds and the effects of organic solvent, salt addition, sampling temperature, and sampling time was studied for SPME. Acetonitrile percentage added to the sample, sample storage conditions (temperature and time), and type of organic elution solvent and elution volume were evaluated for SPE. The results show that both extraction procedures can be used to determine PAHs in drinking waters, but SPE gives better performance (recovery, precision, and quantification limits) for the determination of PAHs in drinking water at the levels established by the legislation.

Chromatography, High Pressure Liquid↗

PubMed2004

Early detection of fungal growth in bakery products by use of an electronic nose based on mass spectrometry.

This paper presents the design, optimization, and evaluation of a mass spectrometry-based electronic nose (MS e-nose) for early detection of unwanted fungal growth in bakery products. Seven fungal species (Aspergillus flavus, Aspergillus niger, Eurotium amstelodami, Eurotium herbariorum, Eurotium rubrum, Eurotium repens, and Penicillium corylophillum) were isolated from bakery products and used for the study. Two sampling headspace techniques were tested: static headspace (SH) and solid-phase microextraction (SPME). Cross-validated models based on principal component analysis (PCA), coupled to discriminant function analysis (DFA) and fuzzy ARTMAP, were used as data treatment. When attempting to discriminate between inoculated and blank control vials or between genera or species of in vitro growing cultures, sampling based on SPME showed better results than those based on static headspace. The SPME-MS-based e-nose was able to predict fungal growth with 88% success after 24 h of inoculation and 98% success after 48 h when changes were monitored in the headspace of fungal cultures growing on bakery product analogues. Prediction of the right fungal genus reached 78% and 88% after 24 and 96 h, respectively.

Aspergillus↗

PubMed2004

Effect of fat nature and aroma compound hydrophobicity on flavor release from complex food emulsions.

Complex food emulsions containing either hydrogenated palm kernel oil (vegetable fat) or anhydrous milk fat (animal fat) were flavored by using different aroma compounds. The fats differed by their fatty acid and triacylglycerol compositions and by their melting behavior, while the aroma compounds (ethyl butanoate, ethyl hexanoate, methyl hexanoate, mesifurane, linalool, diacetyl, cis-3-hexen-1-ol, and gamma-octalactone) differed by their hydrophobicity. Application of differential scanning calorimetry to fat samples in bulk and emulsified forms indicated differences in the ratio of solid-to-liquid between temperatures ranging from 10 to 35 degrees C. Solid-phase microextraction coupled with GC-MS analysis indicated that flavor release from food emulsions containing animal or vegetable fat differed depending on both the fat nature and flavor compound hydrophobicity. The release of diacetyl was higher for emulsions containing animal fat, whereas the release of esters was higher for emulsions containing vegetable fat. The release of cis-3-hexenol, linalool, gamma-octalactone, and mesifurane (2,5-dimethyl-4-methoxy-(2H)-furan-3-one) was very similar for the two fatty systems. The above results were discussed not only in terms of aroma compound hydrophobicity, but also in terms of structural properties of the emulsions as affected by the lipid source.

Animals↗

PubMed2004

Silylation of acrylamide for analysis by solid-phase microextraction/gas chromatography/ion-trap mass spectrometry.

A method for quantitative analysis of acrylamide has been developed for use with headspace solid-phase microextraction (SPME). In the method, acrylamide undergoes silylation with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) to form the volatile N,O-bis(trimethylsilyl)acrylamide (BTMSA). Once formed, BTMSA is readily extracted from the headspace over the silylation reaction using a 100 microm poly(dimethylsiloxane) SPME fiber. A series of experiments was undertaken to optimize the amount of BSTFA, the silylation reaction temperature, the silylation reaction duration, and SPME sampling duration to maximize the analytical sensitivity for BTMSA. Acrylamide levels were quantified relative to a [13C3]-acrylamide internal standard using gas chromatography/ion-trap mass spectrometry (GC/MS) in the single ion monitoring mode. An analytical working curve was constructed and found to be linear over the 4 to 6700 ppb acrylamide range investigated with a limit of detection of 0.9 ppb. The native acrylamide levels of three commercial cereals were measured using the optimized analytical method. Quantitative standard additions of acrylamide to the cereal matrixes demonstrated complete recovery of the spiked acrylamide.

Acetamides↗

PubMed2005

SPME-GC-pyrolysis-AFS determination of methylmercury in marine fish products by alkaline sample preparation and aqueous phase phenylation derivatization.

Characterization of a cost-efficient analytical method based on alkaline sample digestion with KOH and NaOH, followed by aqueous phase phenylation derivatization with NaBPh4 and solid phase microextraction (SPME) for the determination of methylmercury in typical fish-containing food samples commercially available in Hungary, is reported. The sample preparation procedure along with the applied SPME-GC-pyrolysis-AFS system was validated by measuring certified reference materials (CRM) BCR-464, TORT-2, and a candidate CRM BCR 710. To carry out an estimation of average Hungarian methylmercury exposures via marine fish and/or fish-containing food consumption, 16 commercially available products and 3 pooled representative seafood samples of-according to a previous European survey--the three most consumed fish species in Hungary, herring, sardines, and hake, were analyzed. Methylmercury concentrations of the analyzed samples were in the range 0.016-0.137 microg of MeHg g(-1) dry weight as Hg.

Chromatography, Gas↗

PubMed2005

Phenylacetaldehyde O-methyloxime: a volatile compound produced by grapefruit leaves infected with the citrus canker pathogen, Xanthomonas axonopodis pv. citri.

An aldehyde oxime O-methyl ether, phenylacetaldehyde O-methyloxime, was detected using solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS) in the headspace above grapefruit leaves infected with Xanthomonas axonopodis pv. citri, the causal agent of citrus bacterial canker disease (CBCD). This disease is a major phytosanitary concern, and an eradication campaign against it is currently underway in Florida. Phenylacetaldehyde O-methyloxime has been reported to be produced by other plants and fragrant flowers, but it was not observed in the headspace above uninfected grapefruit leaves, the pathogenic bacterium X. axonopodis pv. citri itself, or grapefruit leaves infected with another closely related bacterial pathogen, X. axonopodis pv. citrumelo, which causes citrus bacterial spot, a disease of no phytosanitary significance. It was also not detected from CBCD infected fruits, including orange, lemon, grapefruit, and lime. We conclude that phenylacetaldehyde O-methyloxime may potentially be used to identify CBCD infestations. However, more intensive studies will be required to fully evaluate the potential of phenylacetaldehyde O-methyloxime as a diagnostic compound for CBCD. Using SPME and GC-MS to measure phenylacetaldehyde O-methyloxime may provide an easy and feasible tool to complement current methods used to detect X. axonopodis pv. citri in environmental samples.

Acetaldehyde↗

PubMed2005

Analysis of volatile compounds from various types of barley cultivars.

We identified volatile compounds of barley flour and determined the variation in volatile compound profiles among different types and varieties of barley. Volatile compounds of 12 barley and two wheat cultivars were analyzed using solid phase microextraction (SPME) and gas chromatography. Twenty-six volatiles comprising aldehydes, ketones, alcohols, and a furan were identified in barley. 1-Octen-3-ol, 3-methylbutanal, 2-methylbutanal, hexanal, 2-hexenal, 2-heptenal, 2-nonenal, and decanal were identified as key odorants in barley as their concentration exceeded their odor detection threshold in water. Hexanal (46-1269 microg/L) and 1-pentanol (798-1811 microg/L) were the major volatile compounds in barley cultivars. In wheat, 1-pentanol (723-748 microg/L) was a major volatile. Hulled barley had higher total volatile, aldehyde, ketone, alcohol, and furan contents than hulless barley, highlighting the importance of the husk in barley grain aroma. The proanthocyanidin-free varieties generally showed higher total volatile and aldehyde contents than wild-type varieties, potentially due to decreased antioxidant activity by the absence of proanthocyanidins.

Alcohols↗

PubMed2005

Solid- and vapor-phase antimicrobial activities of six essential oils: susceptibility of selected foodborne bacterial and fungal strains.

The antimicrobial activity of essential oils (EOs) of cinnamon (Cinnamon zeylanicum), clove (Syzygium aromaticum), basil (Ocimum basillicum), rosemary (Rosmarinus officinalis), dill (Anethum graveolens), and ginger (Zingiber officinalis) was evaluated over a range of concentrations in two types of contact tests (solid and vapor diffusion). The EOs were tested against an array of four Gram-positive bacteria (Staphylococcus aureus, Bacillus cereus, Enterococcus faecalis, and Listeria monocytogenes), four Gram-negative bacteria (Escherichia coli, Yersinia enterocolitica, Salmonella choleraesuis, and Pseudomonas aeruginosa), and three fungi (a yeast, Candida albicans, and two molds, Penicillium islandicum and Aspergillus flavus). The rationale for this work was to test the possibility of creating a protective atmosphere by using natural compounds that could extend the shelf life of packaged foodstuffs while minimizing organoleptic alterations. In the solid diffusion tests, cinnamon and clove gave the strongest (and very similar) inhibition, followed by basil and rosemary, with dill and ginger giving the weakest inhibition. The fungi were the most sensitive microorganisms, followed by the Gram-positive bacterial strains. The Gram-negative strain P. aeruginosa was the least inhibited. The composition of the atmosphere generated by the EOs, and their minimum inhibitory concentrations (MICs), were determined using a disk volatilization method, in which no inhibition from rosemary or basil was observed. Cinnamon and clove, once again, gave similar results for every microorganism. As a general rule, MIC (fungi) << MIC (bacteria) with no clear differences between Gram-positive or -negative strains except for P. aeruginosa, which was not inhibited by any of the EOs in the vapor phase. The atmosphere generated from the EOs was analyzed by means of solid-phase microextraction combined with gas chromatography-ion trap mass spectrometry. Differences among the volatiles in the EOs, which may be responsible for the differences in their antimicrobial performances, were found.

Anethum graveolens↗