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Headspace Analysis (headspace + analysis)
Selected AbstractsElectronic Nose Technology in Quality Assessment: Predicting Volatile Composition of Danish Blue Cheese During RipeningJOURNAL OF FOOD SCIENCE, Issue 6 2005Jeorgos Trihaas ABSTRACT This work describes for the 1st time the use of an electronic nose (e-nose) for the determination of changes of blue cheeses flavor during maturation. Headspace analysis of Danish blue cheeses was made for 2 dairy units of the same producer. An e-nose registered changes in cheeses flavor 5, 8, 12, and 20 wk after brining. Volatiles were collected from the headspace and analyzed by gas chromatography-mass spectrometry (GC-MS). Features from the chemical sensors of the e-nose were used to model the volatile changes by multivariate methods. Differences registered during ripening of the cheeses as well as between producing units are described and discussed for both methods. Cheeses from different units showed significant differences in their e-nose flavor profiles at early ripening stages but with ripening became more and more alike. Prediction of the concentration of 25 identified aroma compounds by e-nose features was possible by partial least square regression (PLS-R). It was not possible to create a reliable predictive model for both units because cheeses from 1 unit were contaminated by Geotrichum candidum, leading to unstable ripening patterns. Correction of the e-nose features by multiple scatter correction (MSC) and mean normalization (MN) of the integrated GC areas made correlation of the volatile concentration to the e-nose signal features possible. Prediction models were created, evaluated, and used to reconstruct the headspace of unknown cheese samples by e-nose measurements. Classification of predicted volatile compositions of unknown samples by their ripening stage was successful at a 78% and 54% overall correct classification for dairy units 1 and 2, respectively. Compared with GC-MS, the application of the rapid and less demanding e-nose seems an attractive alternative for this type of investigation. [source] Headspace Evaluation of Methanethiol and Dimethyl Trisulfide in Aqueous Solutions of Soy-protein IsolatesJOURNAL OF FOOD SCIENCE, Issue 5 2000W.L. Boatright ABSTRACT Volatile compounds from 2 samples of aqueous soy-protein isolates (SPI) (7%) were analyzed using both static and dynamic headspace methods. Based on dynamic headspace analyses, the most powerful odorants were (1) dimethyl trisulfide, (2) methanethiol, (3) hexanal, (4) an unidentified charred, sweaty feet-like odor, (5) 2-pentyl furan, (6) 2,3-butadione, and (7) an unknown burnt-like odor. The most powerful odorants by static headspace analyses were (1) dimethyl trisulfide, (2) hexanal, (3) methanethiol, and (4) 2-pentyl furan. Using deuterium labeled DMTS as an internal standard, DMTS was quantified at 60.1 and 45.5 ppb in the SPIs. This corresponds to odor values of 6014 and 4554, respectively. Using a cool, on-column technique, direct injection of concentrated-headspace volatiles and solvent-recovered volatiles with an internal standard of d6 -DMTS detected both methanethiol and DMTS at similar levels as with the traditional injection methods. [source] Seasonal, populational and ontogenic variation in the volatile oil content and composition of individuals of Origanum vulgare subsp.PHYTOCHEMICAL ANALYSIS, Issue 5 2004Hirtum, assessed by GC headspace analysis, by SPME sampling of individual oil glands Abstract Small-scale GC headspace analyses combined with SPME sampling of individual oil glands have been used to measure the variation in volatile content and composition in and within different oregano plants as affected by age, season and developmental state. The main monoterpenes found were p -cymene, carvacrol and their precursor , -terpinene. The early season preponderance of p -cymene over carvacrol was reversed as the season progressed and this pattern could also be seen at any time within the plant, from the latest leaves to be produced (low in cymene) to the earliest (high in cymene). Seedlings from the same mother plant developed this pattern at different rates. Within individual leaves the pattern was not observed, even within the youngest developing leaves. However it was found that the oil composition of individual glands within a single leaf varied considerably, most notably in respect of the production of carvacrol and its isomer thymol. Copyright © 2004 John Wiley & Sons, Ltd. [source] A selective and sensitive approach to characterize odour-active and volatile constituents in small-scale human milk samplesFLAVOUR AND FRAGRANCE JOURNAL, Issue 6 2007Andrea Buettner Abstract A sensitive and selective analytical approach was developed for the characterization of trace volatile and odorous substances in body fluids. The methodology was successfully applied for identification of more than 40 characteristic odorants in human milk. The technique comprises a modified stir bar sorptive extraction system in combination with two-dimensional gas chromatographic separation and parallel mass spectrometric and olfactometric characterization of the analytes. The present study shows that the technique can be used for both direct extractive sampling and headspace analysis, and that it is applicable for small sample volumes. Copyright © 2007 John Wiley & Sons, Ltd. [source] Solid-phase aroma concentrate extraction (SPACEÔ ): a new headspace technique for more sensitive analysis of volatilesFLAVOUR AND FRAGRANCE JOURNAL, Issue 3 2004Masashi Ishikawa Abstract The SPACEÔ (solid-phase aroma concentrate extraction) method is a modi,ed version of the SPME (solid-phase micro extraction) technique for headspace analysis, with increased area of the adsorbent to enable more sensitive analysis of volatiles. The SPACEÔ rod used in the technique is fabricated from stainless steel coated with an adsorbent mixture, consisting mainly of a graphite carbon. Initially, the SPACEÔ rod is ,xed in the head of a closed ,ask, where it adsorbs the aroma. Next, the rod is thermally desorbed on-line with a high-resolution gas chromatography,mass spectrometer (HRGC,MS). In the present experiments, SPACEÔ sampling reproducibility was determined by analysing a standard mixture and roasted coffee beans. The SPACEÔ rod collected the analytes with good reproducibility, with the exception of high polar compounds. Similar analyses of coffee powder were performed by SPME and other methods for comparison with the SPACEÔ method. The SPACEÔ method proved to have superior capabilities with high concentrations, and it produced a well-balanced chromatogram. Copyright © 2004 John Wiley & Sons, Ltd. [source] Determination of the aroma impact compounds in heated sweet cream butterFLAVOUR AND FRAGRANCE JOURNAL, Issue 4 2003D. G. Peterson Abstract This study was conducted to determine which volatile compounds are primarily responsible for the aroma of heated sweet cream butter. Static headspace analysis was used for aroma isolation and gas chromatography,olfactometry (GC,O) for the selection of odour-active components. Quanti,cation of selected odourants was done via purge and trap-GC/mass spectrometry (MS). Nineteen odour-active compounds were detected in the headspace (static) of heated butter (hydrogen sulphide, methanethiol, acetaldehyde, 2,3-butanedione, 1-hexen-3-one, butanoic acid, 3-methylbutanoic acid, 2-heptanone, methional, dimethyl trisulphide, 1-octen-3-one, hexanoic acid, furaneol, , -hexanolactone, nonanal, (E)-2-nonenal, , -octanolactone, skatole and , -decanolactone). Aroma recombination studies followed by sensory analysis indicated that the aroma of our heated butter model was rated the same (similarity) as a heated commercial butter (obtained from local market) in comparison to a heated freshly manufactured butter. The aroma of a heated commercial unsalted butter and a heated butter aroma model of Budin 1 also were signi,cantly less similar than the aroma of our heated butter model in comparison to a heated freshly manufactured butter. Copyright © 2003 John Wiley & Sons, Ltd. [source] Electric-Field Triggered Controlled Release of Bioactive Volatiles from Imine-Based Liquid Crystalline PhasesCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2009Andreas Herrmann Dr. Abstract Application of an electric field to liquid crystalline film forming imines with negative dielectric anisotropy, such as N -(4-methoxybenzylidene)-4-butylaniline (MBBA, 1), results in the expulsion of compounds that do not participate in the formation of the liquid crystalline phase. Furthermore, amines and aromatic aldehydes undergo component exchange with the imine by generating constitutional dynamic libraries. The strength of the electric field and the duration of its application to the liquid crystalline film influence the release rate of the expelled compounds and, at the same time, modulate the equilibration of the dynamic libraries. The controlled release of volatile organic molecules with different chemical functionalities from the film was quantified by dynamic headspace analysis. In all cases, higher headspace concentrations were detected in the presence of an electric field. These results point to the possibility of using imine-based liquid crystalline films to build devices for the controlled release of a broad variety of bioactive volatiles as a direct response to an external electric signal. [source] Use of Volatiles as Indicators of Lipid Oxidation in Muscle FoodsCOMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY, Issue 1 2006Carolyn F. Ross ABSTRACT Lipid oxidation has long been recognized as a leading cause of quality deterioration in muscle foods and is often the decisive factor in determining food product storage life. Lipid oxidation generates a number of products, including volatile compounds, which are the major contributors to the development of rancid off-flavors and odors. Over the years, methodologies have been developed to quantify lipid oxidation products in muscle foods. This article reviews the analytical methods that have been used to quantify volatile compounds as indicators of lipid oxidation in muscle foods. The sampling methodologies of distillation/solvent extraction and headspace analysis, and isolation methods associated with gas chromatographic (GC) and high-performance liquid chromatography (HPLC) analyses are discussed. Within gas chromatographic methodologies, headspace (HS) sampling (static HS, dynamic purge-and-trap HS techniques, and solid-phase microextraction [SPME]) are addressed. 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