Dynamic Headspace Gas Chromatography Research Articles

Analytical methods for the determination of the geographic origin of Emmental cheese: volatile compounds by GC/MS-FID and electronic nose

The volatile compounds of Emmental cheese of different origins were investigated to check their suitability as markers of geographic origin. A total of 20 Emmental cheese samples from Switzerland, Allgau (D), Bretagne (F), Savoie (F), Vorarlberg (A) and Finland (produced in winter with a ripening time according to that sold in the corresponding regions) were analysed using dynamic headspace gas chromatography followed by flame ionisation and mass spectrometry. All regions were easily differentiated by using compounds occurring only in the corresponding region or by combining a few compounds by principal component analysis (PCA). Further analyses were carried out using a mass spectrometry-based electronic nose. PCA achieved 90 and 91% of correct classifications for the Emmental from Switzerland and other regions, respectively.

Light-induced colour and aroma changes in sliced, modified atmosphere packaged semi-hard cheeses

Abstract Sliced Samso cheese, stored up to 3 weeks, exposed to light (1500 lx), packaged in 0% CO 2 (100% N 2 ), 20% CO 2 (80% N 2 ), or 100% CO 2 showed a significant decrease in yellowness ( b* ) and an increase in redness ( a* ). Cheese packaged in atmospheres containing 100% CO 2 and exposed to light was significantly darker ( L* ) than cheese exposed to 0% CO 2 , and the 100% CO 2 resulted in a drying-out of the cheeses. Descriptive sensory analysis revealed that light, gas composition, and storage time significantly affected taste and odour attributes of the semi-hard Samso cheese. Assessors characterised dark-stored cheeses packed in 20% CO 2 or 0% CO 2 as the most buttermilk-like. Cheeses packed in 100% CO 2 and exposed to light were described as rancid and as having a dry/crumbly texture. Dynamic headspace gas chromatography–mass spectrometry was used to identify volatile compounds. Significant light exposure effects during storage were noted for the following oxidation products: 1-Pentanol, 1-octanol, 2-ethyl-1-butanol, 2-butanol, 2-heptanol, 2-pentanol, 2-nonanol, benzaldehyde, 2-butanone, 2-nonanone, dimethyl trisulfide, and tetrahydrofuran. The gas composition had no impact on the formation of volatiles.

Dynamic Headspace Analysis of Volatile Constituents of Swiss Cheese Whey Protein Concentrate

Volatile flavor compounds in the headspace of swiss cheese whey protein concentrate (WPC) were analyzed by dynamic headspace analyzer, gas chromatography, and mass spectrometer. Sixty one compounds were detected from the headspace of dry WPC and 23 compounds from the headspace of an aqueous solution of WPC. The major components were propanol, hexanal, 2-butanone, 2-pentanone, 2,3-butanedion, 2-propanol, acetic acid, dimethyl disulfide and benzothiazole. An external dynamic headspace sampler, devised for this study, effectively collected volatiles from the headspace of dry WPC and aqueous WPC solutions.

High trimethylamine concentration in milk from cows on standard diets is expressed as fishy off-flavour.

To establish whether fishy off-flavour observed in cows' milk in Sweden is due to abnormal concentrations of trimethylamine (TMA) in milk, 15 milk samples from 13 cows of the Swedish Red and White breed (SRB) were analysed for this compound using dynamic headspace (DHS) gas chromatography (GC). A mass selective detector (MSD) was used for the qualitative and a flame ionization detector (FID) for the quantitative analyses. Further confirmation was obtained using a solid phase microextraction (SPME) followed by GC-olfactometry (GC-O) and GC-NPD (nitrogen and phosphorus detector). Samples were also evaluated by a two-person organoleptic panel for the presence of fishy off-flavour. Results showed that the seven milk samples with a fish-like taint contained > 1 mg TMA/kg milk, whereas, with a single exception, the seven samples that were judged to be normal did not contain this compound. Furthermore, there were indications of a dose-dependent relationship between TMA concentration and fishy off-flavour score.

SENSORY AND INSTRUMENTAL FLAVOR ANALYSES OF CHEESE CURD COCULTURED WITH SELECTED YEAST AND BACTERIA

ABSTRACTRelationships between odor properties and volatile chemical composition were explored on 39 cocultures of three different yeasts, three Geotrichum candidum and five bacteria, commonly used in bacteria and mold surface ripened cheese. Sensory profiling was performed by ten trained judges by scoring the intensity of 14 odor attributes. At the same time, the volatile compounds of the cocultures were extracted and analyzed by dynamic headspace gas chromatography and mass spectrometry. Sensory and instrumental data were compared and correlated using correlation analysis and partial least squares regression analysis. The sample plot including the whole set of samples evidenced a clustering of the associations containing the yeast strain Kluyveromyces lactis and any bacteria. They developed strong fruity olfactory notes related to their high content of ethyl esters and various alcohols. The sample plot on a restricted set of samples evidenced the fruity characteristics of Debaryomyces hansenii and bacteria associations and the cheesy odors of Yarrowia lipolytica and Geotrichum candidum cocultures that produced sulfur compounds.

Determination of trimethylamine in milk using an MS based electronic Nose

A simple, rapid, reliable and highly automated analytical method has been developed to determine trimethylamine (TMA) in milk using an MS based electronic nose (SMart Nose). A set of Swedish milk samples with and without naturally occurring TMA was used to compare this new method with sensory analysis and dynamic headspace (DHS) gas chromatography with flame ionisation detection (GC-FID). The results show good agreement between these three analytical methods. A lower detection limit (0.5 mg kg–1) and better repeatability were achieved with this new method compared to both sensory and DHS GC-FID analyses (1–2 mg kg–1). The user-friendly multivariate analysis software provided with the SMart Nose system was used for TMA determination via a numerical PCA. Using Excel, peak intensity, correlated with TMA concentration via a second order equation, gave similar results. Thus, this is an up to date method of choice for the quantitative determination of TMA in milk. It is also able to give further qualitative information on the milk analysed using the PCA analysis supplied with this equipment.

Interactions between non-volatile water-soluble molecules and aroma compounds in Camembert cheese

Abstract Interactions between selected aroma compounds and non-volatile water-soluble molecules were studied using dynamic headspace-gas chromatography. A model water-soluble extract (MWSE), previously constructed in gustatory and physico-chemical accordance with the crude Camembert cheese WSE, allowed the contribution of non-volatiles to the headspace composition of volatile compounds to be assessed. The presence of the MWSE increased the headspace concentration of 2-heptanone, 1-octen-3-ol and 3-methylbutanol, showing that these three volatile compounds were released by MWSE. Omission tests performed on MWSE allowed for the impact of each MWSE component on aroma compounds release to be determined. The releasing influence of minerals appeared as the main effect observed for the three volatiles, despite some retention phenomena due to other MWSE components also occurring. In the case of 2-undecanone, 2-nonanol, 2,4-dithiapentane and ethylhexanoate, which were not affected by the presence of MWSE, some significant compensatory effects were observed. Whereas amino acids had no significant effect, minerals might cause their release and the presence of peptides can either decrease or increase headspace concentration of aroma compounds. Possible antagonistic effects between MWSE components are discussed.

Formation of chloroform in spruce forest soil – results from laboratory incubation studies

The release of chloroform, 1,1,1-trichloroethane, tetrachloromethane, trichloroethene and tetrachloroethene from an organic rich spruce forest soil was studied in laboratory incubation experiments by dynamic headspace analysis, thermodesorption and gas chromatography. Performance parameters are presented for the dynamic headspace system. For spruce forest soil, the results showed a significant increase in chloroform concentration in the headspace under aerobic conditions over a period of seven days, whereas the concentration of the other compounds remained fairly constant. A biogenic formation of chloroform is suggested, whereas for the other compounds anthropogenic sources are assumed. The addition of trichloroacetic acid to the soil increased the release of chloroform from the soil. It is, therefore, suggested that trichloroacetic acid also contributed to the formation of chloroform. Under the experimental conditions, the spruce forest soil released chloroform concentrations corresponding to a rate of 12 μg m −2 day −1. Data on chloroform production rates are presented and compared with literature results, and possible formation mechanisms for chloroform are discussed.

Development of rancidity in wheat germ analyzed by headspace gas chromatography and sensory analysis.

Wheat germ is susceptible to oxidation due to its high content of unsaturated oil. Volatile compounds in stored wheat germ were evaluated using dynamic headspace gas chromatography (HS-GC) and sensory analysis. Preliminary comparisons were also made between freshly prepared wheat germ and wheat germ subjected to microwave heating at 45 and 55 degrees C prior to storage at room temperature. The progress of oxidation was followed in untreated wheat germ for 4 weeks and in heat-treated wheat germ for 7 weeks by HS-GC and sensory evaluation. Significant (p < 0.05) changes in rancid odor and flavor were observed in the untreated wheat germ after 3 weeks, whereas no corresponding difference was observed in the microwave-heated wheat germ after 7 weeks of storage. Identification of a total of 36 volatile compounds was performed according to their mass spectra and Kovats indices. The major volatiles were hexanal, alpha-pinene, 1-hexanol, and 3-carene. In addition to analysis of a short period of storage, 30 volatile compounds were identified from the headspace of wheat germ stored for >1 year.

The Analysis of Fire Debris for the Presence of Propan-2-ol Using Dynamic Headspace Concentration and Gas Chromatography with Flame Ionization Detection

Abstract We describe a simple procedure for the identification of propan-2-ol in fire debris. Vapors collected from samples of debris at elevated temperatures, were subsequently dissolved in water prior to being analyzed by headspace gas chromatography with flame ionization detection.

Oxidation mechanisms in real food emulsions: oil-water partition coefficients of selected volatile off-flavor compounds in mayonnaise

A method for the determination of oil/water partition coefficients, P o/w, for volatile lipid oxidation products in mayonnaise enriched with fish oil has been developed. Selected volatile off-flavor compounds (2-pentenal, 3-heptanone, octanal, 1-octen-3-ol, 2,4-heptadienal, and 2-nonanone) were added in levels ranging from 80 to 480 ng/g mayonnaise. The mayonnaises were separated by a procedure involving freezing, centrifugation, and ultracentrifugation. The P o/w values were then determined from the concentrations of volatiles quantified by dynamic headspace gas chromatography on the separated lipid and aqueous phases. The P o/w values for the selected volatiles ranged from 4.9 to infinity. Increased addition levels of the six volatile compounds resulted in an increase of the apparent P o/w values and higher recoveries of the volatiles. Also, the effect on P o/w values of an additional emulsifier (Panodan TR) and three different antioxidant systems (Grindox 1032, Toco 70, and ascorbic acid) added to mayonnaise was studied. Addition of ascorbic acid seemed to increase recoveries, which resulted in higher P o/w values. In contrast, addition of extra emulsifier and a water dispersible tocopherol preparation (Grindox 1032) resulted in lower P o/w values and lower recoveries for analysis. We propose that the effect of Grindox 1032 addition may be due to the ability of this antioxidant preparation, via its emulsifier content, to promote increased binding or entrapment of volatile compounds at the oil/water interface of mayonnaise. The data may be useful for selecting antioxidant and emulsifier systems to mask off-flavor development in food emulsion systems.

Effect of extraction conditions on sensory quality of virgin olive oil

AbstractThe 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&lt;30 min) could also be useful as an alternative way to obtain pleasant green virgin olive oils.

Quantification of 2-Methyl-3-furanthiol, 2-Furfurylthiol, 3-Mercapto-2-pentanone, and 2-Mercapto-3-pentanone in Heated Meat

A stable isotope dilution assay was developed for quantification of the potent odorants 2-methyl-3-furanthiol (MFT), 2-furfurylthiol (FFT), 2-mercapto-3-pentanone (2M3P), and 3-mercapto-2-pentanone (3M2P) in heated meat. The volatiles of meat were extracted with dichloromethane, which was spiked with definite amounts of stable isotopomers of MFT, FFT, and 3M2P. The analytes and their labeled standards were enriched by reaction with p-hydroxymercuribenzoic acid, and after liberation, the thiols were assayed by dynamic headspace gas chromatography in combination with mass spectrometry. The following amounts (micrograms per kilogram) were found in meat samples boiled for 45 min: (beef) MFT, 7−28, FFT, 13−42, 3M2P, 55−73, 2M3P, 20−44; (pork) MFT, 6−9, FFT, 8−10, 3M2P, 66−117, 2M3P, 11−14; (lamb) MFT, 5−11, FFT, 9−14, 3M2P, 30, 2M3P, 10. Chicken contained per kilogram 4.5 μg of MFT, 2.4 μg of FFT, 100 μg of 3M2P, and 13 μg of 2M3P after a boiling period of 60 min. Keywords: Isotope dilution assay; 2-methyl-3-furanthiol; 2-furfurylthiol; 3-mercapto-2-pentanone; 2-mercapto-3-pentanone; beef; chicken; pork; lamb; flavor

Analysis of volatiles from callus cultures of olive Olea europaea

The lipoxygenase pathway in olive fruit gives rise to volatile products which influence the aroma of the harvested oil. In this study dynamic headspace gas chromatography was used in order to investigate volatile production by different olive cultivars. Olive callus cultures were used as a model for this purpose, because of the ease of standardising the growth conditions of the calli compared to working with field-grown material. The cultures contained substantial amounts of the polyunsaturated fatty acids, linoleate and α-linolenate, which are the normal substrates for lipoxygenases. Most of the major volatiles that characterise virgin olive oil were also produced by the cultures, especially the unsaturated and saturated C 6 aldehydes, alcohols and their acetyl esters. Moreover, by means of ANOVA test, a strong effect of cultivar on volatile production in olive cultures was clearly established. This agreed with data for olive oils from different cultivars, which are also easily distinguished by headspace gas liquid chromatography. We have also demonstrated that changing the culture conditions for temperature and pH produced qualitative and quantitative alterations in volatile production.

Physicochemical Characteristics of Selected Sweet Cherry Cultivars.

The volatile, sugar, and organic acid constituents in 12 cultivars and selections of sweet cherries (Prunus avium L.) were characterized and quantified by high-performance liquid chromatography and gas chromatography (GC). Fruit weight, soluble solids concentration (SSC), pH, titratable acidity (TA), and color (CIE L, a, b) were also determined at harvest. Weight ranged from 8.8 to 14.5 g per fruit, SSC from 13.5 to 24.5 degrees Brix, and SSC/TA ratio from 18.3 to 29.0. Chroma was a better indicator of color variations among sweet cherry cultivars compared to the hue angle as it correlated highly with L, a, and b values (r > 0.90). The major nonvolatile constituents varied widely among cultivars: glucose [5.2-8.8 g/100 g of fresh weight (FW)], fructose (4.4-6.4 g/100 g of FW), sorbitol and mannitol (2.2-8.0 g/100 g of FW), and malic acid (502.7-948.3 mg/100 g of FW). Three principal components accounted for 53.3% of the total variation among 50 volatile compounds assessed by a dynamic headspace GC method. (E)-2-Hexenol, benzaldehyde, hexanal, and (E)-2-hexenal were predominant flavor volatiles and could be used to segregate commercial and new cherry selections into various subgroups.

Classification of Microbial Defects in Milk Using a Dynamic Headspace Gas Chromatograph and Computer-Aided Data Processing. 1. Principal Component Similarity Analysis

There is a need for reliable objective tests for the detection of off-flavors of milk, some of which are caused by bacteriological growth. The objective of the study was to distinguish abnormal from normal milk samples using a low-cost headspace gas chromatograph and principal component similarity analysis. UHT-sterilized milk was inoculated with Pseudomonas fragi, Pseudomonas fluorescens, Bacillus subtilis, Enterobactor aerogenes, Lactococcus lactis, and a mixed culture (P. fragi:E. aerogenes:L. lactis = 1:1:1) to approximately 4.0 log10 CFU mL-1. The samples were stored at 4 °C for 10 days for P. fragi and P. fluorescens and 30 °C for 24 h for the remaining bacteria. A new multiavariate analysis technique, principal component similarity analysis, was capable of distinguishing milk samples inoculated with P. fragi, P. fluorescnes, L. lactis, E. aerogenes, and a mixed culture from uninoculated samples. Keywords: Dynamic headspace gas chromatography; principal component similarity analysis; mulivariate ana...

Dynamic Headspace Gas Chromatography Combined with Multivariate Analysis to Classify Fresh and Processed Orange Juices

Sixty-two commercially processed and fresh orange juice samples were analyzed by headspace gas chromatography to quantify 46 volatile constituents in each sample. Computer multivariate analysis was then used to classify these juices into three types based on degree of processing employed. The three types were unpasteurized, pasteurized not from concentrate and reconstituted to single strength from frozen concentrated juice. Principal components (PC) analysis using the first three PC's in a three dimensional graphics plot was the most effective means of classification for these samples. The computer program also provided information regarding the constituents most important to this classification technique. Such classification has potential for use in quality control and in improving quality of processed orange juices.

Biochemical activities of Micrococcaceae and their effects on the aromatic profiles and odours of a dry sausage model

Micrococcaceae are used as starter cultures in fermented meat, it is therefore important to determine their biochemical activities and especially their aroma producing potential. With this aim, 19 strains of Micrococcaceae were studied in a dry-sausage model. Odours of the samples were assessed by a trained panel. Volatile compounds were analysed by dynamic headspace gas chromatography–mass spectrometry. Strains belonging to the species Staphylococcus warnerior Staphyloccocus saprophyticusthat were both lipolytic and unable to reduce nitrate, developed putrid, nauseous or bread odours. These samples were characterized by high desorption of aldehydes (heptanal, hexanal, octanal), 3-hydroxy butan-2-one and 2, 3-butanedione. The highest dry-cured odour was developed with the inoculation of strains of Staphylococcus carnosusand Staphylococcus xylosuswhich had low lipolytic and proteolytic activities and did not produce acetoin but effectively reduced nitrate. Their inoculation in the sausage model was associated with the greatest desorbtion of 3-methyl butanal, methylketones and ethyl esters and the lowest desorption of alkanes and 3-hydroxy butan-2-one and 2, 3-butanedione.

Chemical Characterization of Raw Milk Samples with and Without Oxidative Off-Flavor

Milk samples with and without oxidized flavor were obtained from two different commercial dairy herds. Milk components that are important for the susceptibility of milk fat to spontaneous oxidation, (i.e., fatty acid composition and the concentrations of α-tocopherol, β-carotene, and ascorbic acid) were analyzed to describe the variation in the susceptibility of milk fat to oxidation in raw milk. The samples were also analyzed using dynamic headspace gas chromatography to determine volatile oxidation products, primarily straight-chain aldehydes.The results showed that milk samples exhibiting off-flavor had higher linoleic acid content in the neutral fat fraction. At one farm, the concentrations of both α-tocopherol and β-carotene were lower in samples that demonstrated off-flavor. At the other farm, this difference was not statistically significant. Milk with off-flavor also had significantly higher concentrations of hexanal.The data were also analyzed by principal component regression. The results from this analysis indicated that the causative factors for the oxidation were different for the two herds.

ChemInform Abstract: Canola Oil Flavor Quality Evaluation by Dynamic Headspace Gas Chromatography.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.