Volatile Components (volatile + component)

Distribution by Scientific Domains

Selected Abstracts

Reduction of Levels of Volatile Components Associated with the "Beany" Flavor in Soymilk by Lactobacilli and Streptococci

Trenna D. Blagden
ABSTRACT: Methanol, acetaldehyde, ethanol, and hexanal were the 4 major volatiles detected in unfermented soymilk. Eight of the cultures of lactobacilli or streptococci completely eliminated hexanal in the soymilk during fermentation. However, there were considerable variations in the effects of the cultures on the other 3 compounds. All 8 caused significant reduction in levels of methanol. Streptococcus thermophilus OSU-2 was the only culture that significantly lowered the concentration of ethanol in the soymilk. All except Lactobacillus acidophilus C19 and Lactobacillus casei E5 significantly lowered the level of acetaldehyde. Of the cultures tested, L. acidophilus L1 offered the best potential for producing fermented soymilk with an improved volatile profile. [source]

Changes in Volatile Components of Stored Tangerines and Other Specialty Citrus Fruits with Different Coatings

R.D. Hagenmaier
ABSTRACT: Shellac and wax-based citrus coatings were applied to Fallglo, Robinson, Sunburst, Dancy and Murcott tangerines, Nova and Orlando tangelos, and Temple oranges. Flavor volatiles were measured before and after storage. Concentrations of ethyl acetate, ethyl butyrate, isopentanol and 2-methyl-3-buten-2-ol increased markedly for fruit with shellac-based coatings, and were highly correlated with ethanol content, but at different ratios for the different varieties. The concentration increases were relatively less for fruit coated with the wax-based coatings, and suggest that high-gloss shellac and resin-based coatings are not appropriate for tangerines. [source]

Analysis of the Volatile Components in the Leaves of Cinnamomum camphora by Static Headspace Gas Chromatography Mass Spectrometry Combined with Accurate Weight Measurement

Fengjun Zhu
Abstract The volatile components in the leaves of C. camphora were analyzed by static headspace-gas chromatography/mass spectrometry (HS-GC-MS) combined with accurate weight measurement. Accurate weight measurement obtained by Time-of-Flight mass spectrometry (TOF-MS) helped to confirm the identification of volatiles in the analysis. 59 volatile components in the leaves of C. camphora were identified, which mainly included cis -3-hexen-1-ol (5.6%), 3-hexen-1-ol, acetate (Z) (11.1%), , -caryophyllene (15.4%), bicyclogermarene (8.4%), trans -nerolidol (19.5%) and 9-oxofarnesol (7.7%). The results show that method using HS-GC-MS combined with accurate weight measurement achieves reliable identification and has extensive application in the analysis of volatile components present in complex samples. [source]

Volatile components of Thymus vulgaris L. from wild-growing and cultivated plants in Jordan

M. Hudaib
Abstract The composition of the essential oil hydrodistilled from the aerial parts of Thymus vulgaris L. grown in Jordan has been determined by GC and GC,MS. Variations in oil composition and yield between cultivated and wild-growing plants collected from different localities, at different altitudes, have been also evaluated. Higher oil yields were observed in plants growing wild (3.7,5.6% of dried material) than in cultivated plants (1.1,2.0%), and those collected from the Mshaqar region, in the middle of Jordan and at the highest altitude, were the richest in oil (,5.4%). Generally, the oil was characterized by marked levels of phenolic monoterpenoids (mainly thymol and carvacrol) in the range 70.8,89.0%. High levels of the monoterpenoid hydrocarbons p -cymene (3.4,8.2%) and , -terpinene (1.6,7.7%) were also observed. Other major components were 1,8-cineole (up to 2.1%), , -thujone (up to 1.2%), camphor (up to 1.1%) and , -caryophyllene (0.2,2.8%). With the exception of plants growing wild in the Ramtha region, in the far north of Jordan, carvacrol was found as the principal phenol of all other oils (50.6,86.1%) and was dominant (>85%) in wild plant oils. The oil from Ramtha was characterized by the highest level of thymol (,63.8%) as the dominant phenol and was most abundant in p -cymene (8.2%), 1,8-cineole (2.1%) and , -terpinene (7.7%). In addition to assigning carvacrol or thymol chemotypes to the plant, the high content of active monoterpenoid phenols strongly suggests a potential use of Jordanian thyme oil in cough products and antimicrobial,herbal drug combinations. Copyright 2007 John Wiley & Sons, Ltd. [source]

Analysis and characterization of aroma-active compounds of Schizandra chinensis (omija) leaves

Cheng Hao Zheng
Abstract Volatile components from leaves of Schizandra chinensis (omija), a native plant of Korea, were extracted by simultaneous distillation,extraction (SDE) and analyzed by gas chromatography,mass spectrometry (GC-MS) using two types of capillary column with different polarities (DB-5MS and DB-Wax). The GC-MS analysis of volatile compounds obtained by SDE revealed that germacrene D is the most abundant compound (22.6%) in omija leaves, followed by ,-elemene (17.4%), (E)-2-hexenal (8.7%), and (E)-,-ocimene (7.2%). Aroma-active compounds were determined by gas chromatography,olfactometry (GC-O) using the aroma-extract-dilution analysis method. (E,Z)-2,6-Nonadienal (cucumber) was the most intense aroma-active compound due to its higher flavor-dilution factor (243,729) than any other compound. (Z)-3-Hexenal (green/apple), (E)-2-hexenal (green/fruity), and (E)-,-ocimene (wither green/grass) were also identified as important aroma-active compounds by GC-O. In addition, the volatile compounds were extracted by solid-phase microextraction (SPME), and the quantitative analysis of the SPME samples gave slightly different results, depending on the type of SPME fiber, compared with those from SDE, However, the aroma-active compounds identified in SPME were similar to those in SDE. Copyright 2004 Society of Chemical Industry [source]

Volatile components of raw and smoked black bream (Brama raii) and rainbow trout (Oncorhynchus mykiss) studied by means of solid phase microextraction and gas chromatography/mass spectrometry

Mara D Guilln
Abstract Solid phase microextraction followed by gas chromatography/mass spectrometry of raw and smoked black bream and rainbow trout was carried out. The volatile components of the raw fish belong to a limited number of groups of compounds. Raw black bream has a higher presence of acids than raw trout, while the latter contains more alcohols, hydrocarbons, esters and phenol derivatives; both contain similar concentrations of saturated aldehydes. The volatiles of the smoked fish basically comprise the compounds also detected in the raw fish together with others produced during the processing. Smoke components detected in both smoked fish species were mainly phenol, guaiacol and syringol derivatives, ketones, acetic acid and some polycyclic aromatic hydrocarbons. Smoked black bream contained a higher number and higher concentrations of smoke components than smoked rainbow trout. Large variations in concentrations of smoke components in the smoked fish samples indicated that the smoking process had not been totally homogeneous. The presence of autoxidatively derived compounds, such as unsaturated aldehydes, was mainly detected in some smoked bream samples, showing that this degradation process is not occurring homogeneously. The usefulness of the applied techniques for the study of volatile components of raw and smoked fish is shown. 2002 Society of Chemical Industry [source]

Chemistry and genotoxicity of caramelized sucrose

David D. Kitts
Abstract Caramelization of a 1% sucrose solution at 180C accompanied characteristic changes in pH, Mr, UV-absorbance, and fluorescence values as well as increased reducing power activity after 40,60 min. Similar changes occurred to sucrose heated at 150C, after 150,240 min. Bioactivity of caramelized sucrose samples was tested for mutagenic activity, using Salmonella typhimurium strains TA-98 and TA-100, respectively, as well as the Saccharomyces D7 yeast strain for mitotic recombination and Chinese hamster ovary cells (CHO) to assess clastogenicity. Caramelized sucrose expressed no mutagenicity in the TA-98 strain, but gave positive (p < 0.05) results with the TA-100, base-pair substitution strain. Similarly, mitotic recombination in the Saccharomyces D7 yeast strain and clastogenic activity in CHO cells were induced when exposed to caramelized sucrose. In the all cases, preincubation with S-9 reduced (p < 0.05) the mutagenic activities of caramelized sucrose. Fractionation of the caramelized sucrose into volatile and nonvolatile compounds was performed and tested for clastogenicity using CHO cells. Volatile components contributed approximately 10% to total clastogenicity, which was enhanced by the presence of S-9. Nonvolatile components recovered, consisting of relatively lower Mr, gave highest (p < 0.05) clastogenic activity, denoting that higher Mr caramel colors are relatively free of this property. [source]

Histochemical localization of secretion and composition of the essential oil in Melittis melissophyllum L. subsp. melissophyllum from Central Italy

Filippo Maggi
Abstract The distribution and morphology of the secretory structures in Melittis melissophyllum L. subsp. melissophyllum (Lamiaceae) were studied for the first time by light and scanning electron microscopy. The indumentum of the vegetative and reproductive organs includes non-glandular hairs and peltate (type A) and capitate (types B and C) glandular trichomes. Histochemical techniques enabled specific location of the site of essential oil accumulation in the type A peltate hairs. In order to confirm the occurrence of the 1-octen-3-ol chemotype in central Italy, six populations growing in different places were analysed for the essential oil composition by GC,FID and GC,MS. In all populations, 1-octen-3-ol was detected as the major volatile component, representing 56.3,70.6% of the total oils. To date, these percentages are the highest detected in a plant essential oil. Copyright 2009 John Wiley & Sons, Ltd. [source]

Coordination complexes of functionalized pyrazines with metal ions: reagents for the controlled release of flavourant molecules at elevated temperatures

Colin Baillie
Abstract The potential for stabilization of volatile flavourant molecules such as functionalized pyrazines by coordination to metal ions, and the application of the resultant coordination complexes as controlled release agents at elevated temperatures were explored. New complexes containing the flavourant molecules 2,3,5-trimethylpyrazine (TMP), 2-ethyl-3-methylpyrazine (EMP) and 2-acetylpyrazine (ACP) with copper(II) and copper(I) salts were prepared and structurally characterized. Representative examples of known copper(II) and calcium(II) complexes containing pyrazine carboxylic acids were also prepared. The complexes were examined by thermal analysis techniques and demonstrated, by a combination of thermogravimetric (TGA) and pyrolysis GC,MS analyses, to act as convenient reagents for the release of the parent pyrazine at elevated temperatures. Thus, pyrolysis GC,MS revealed that the complex [Cu3Cl3(EMP)2]n cleanly releases EMP in 96.5% selectivity at 200 C. Of particular significance is that the calcium complex [Ca(3-aminopyrazine-2-carboxylate)2H2O], under ramped pyrolysis conditions, was shown to undergo decarboxylation prior to the release of 2-aminopyrazine (AMP), as essentially the only volatile component, in the temperature range 600,800 C. This finding provides a precedent for the application of complexes of pyrazinecarboxylate salts with metal ions (of which an almost infinite number of combinations is potentially available) as controlled release agents of the parent pyrazine molecule at elevated temperatures, suitable for exploitation by the foodstuffs, flavour and fragrance industries. Copyright 2006 John Wiley & Sons, Ltd. [source]

Identification of methyl salicylate as the principal volatile component in the methanol extract of root bark of Securidaca longepedunculata Fers

T. K. Jayasekara
Abstract Securidaca longepedunculata Fers (Polygalaceae) is commonly used as a medicine in many parts of Africa and shows promise for protecting stored grain against insect pests. Analysis of a methanol extract of the root bark by gas chromatography linked to mass spectrometry (GC/MS) showed a major component accounting for over 90% of the volatile material. This was identified as methyl 2-hydroxybenzoate (methyl salicylate) by comparison of the GC retention times and mass spectrum with those of synthetic standards. This conflicts with an earlier report that the major component is methyl 4-hydroxybenzoate. Two minor components had mass spectra characteristic of 2-hydroxybenzoate esters and were identified as methyl 2-hydroxy-6-methoxybenzoate and its benzyl analogue, again conflicting with an earlier report. Copyright 2002 John Wiley & Sons, Ltd. [source]

Image-intensified video results from the 1998 Leonid shower: I. Atmospheric trajectories and physical structure

Precise heights and light curves were obtained for 79 Leonid meteors that ranged in brightness (at maximum luminosity) from +0.3 to +6.1 astronomical magnitude. The mean photometric mass of the data sample was 1.4 10,6 kg. The dependence of astronomical magnitude at peak luminosity on photometric mass and zenith angle was consistent with earlier studies of faint sporadic meteors. For example, a Leonid meteoroid with a photometric mass of ,1.0 10- 7 kg corresponds to a peak meteor luminosity of about +4.5 astronomical magnitudes. The mean beginning height of the Leonid meteors in this sample was 112.6 km and the mean ending height was 95.3 km. The highest beginning height observed was 144.3 km. There is relatively little dependence of either the first or last heights on mass, which is indicative of meteoroids that have clustered into constituent grains prior to the onset of intensive grain ablation. The height distribution, combined with numerical modelling of the ablation of the meteoroids, suggests that silicate-like materials are not the principal component of Leonid meteoroids and hints at the presence of a more volatile component. Light curves of many Leonid meteors were examined for evidence of the physical structure of the associated meteoroids: similar to the 1997 Leonid meteors, the narrow, nearly symmetric curves imply that the meteoroids are not solid objects. The light curves are consistent with a dustball structure. [source]

Detection of the Sexual Identity of Conspecifics through Volatile Chemical Signals in a Territorial Salamander

ETHOLOGY, Issue 3 2007
Benjamin J. Dantzer
Territorial red-backed salamanders (Plethodon cinereus) have been shown to use nonvolatile chemical signals in both territorial defense and to convey a variety of information to conspecifics. We investigated whether or not red-backed salamanders could determine the sexual identity of conspecifics through volatile chemical signals, and we explored their use in the context of territorial defense. We exposed male and female red-backed salamanders to four experimental treatments (i.e. filter papers that had been scent marked by male or female conspecifics for 1 and 5 d) and two control treatments (i.e. unscented filter papers for 1 and 5 d tests). The focal salamanders were prevented from physically accessing the scent marked filter papers and, presumably, some of the substrate scent marks had volatile components that were detected and interpreted by the focal salamanders. Both male and female red-backed salamanders spent significantly more time in threat displays when they were exposed to volatile chemical signals from same-sex conspecifics than they did toward similar signals from opposite-sex conspecifics. A similar statistical pattern was observed for the amount of chemosensory sampling exhibited by focal red-backed salamanders. From these results, we infer that red-backed salamanders can determine the sexual identity of conspecifics through volatile chemical signals, some of which may be used in territorial defense. Further, such airborne pheromones may influence the spatial organization of salamander territories on the forest floor. [source]

Volatile compounds of original African black and white shea butter from Tchad and Cameroon

Sabine Krist
Abstract Shea butter is used as an edible vegetable fat in many African countries. It can be utilized as a substitute or complete replacement for cocoa butter in various applications and plays an important role in traditional African medicinal practice. Although detection of volatile compounds by solid-phase micro-extraction gas-chromatography mass-spectroscopy (SPME-GC-MS) is a very reliable and reproducible technique, which can be used as an important part of authenticity checking, production monitoring and contamination detection, no published data about volatile compounds of shea butter are available so far. In this investigation, the characteristic volatiles in the headspace of original African shea butter samples were identified by using SPME-capillary-GC coupled to a mass selective detector. Almost 100,different volatile components were identified, e.g. fatty acids, saturated and unsaturated aldehydes and ketones, terpenes, and typical Maillard reaction products such as methylfuranes and pyrazines. Furthermore, the samples have been olfactorily evaluated by a panel of professional flavorists and trained analytical chemists. It can be stated that variations in processing conditions of shea butter result in considerable differences in the composition of headspace volatiles, detected by SPME-GC-MS and human olfaction. [source]

Factors affecting secondary metabolite production in plants: volatile components and essential oils

A. Cristina Figueiredo
Abstract The presence, yield and composition of secondary metabolites in plants, viz. the volatile components and those occurring in essential oils, can be affected in a number of ways, from their formation in the plant to their final isolation. Several of the factors of influence have been studied, in particular for commercially important crops, to optimize the cultivation conditions and time of harvest and to obtain higher yields of high-quality essential oils that fit market requirements. In addition to the commercial importance of the variability in yield and composition, the possible changes are also important when the essential oils and volatiles are used as chemotaxonomic tools. Knowledge of the factors that determine the chemical variability and yield for each species are thus very important. These include: (a) physiological variations; (b) environmental conditions; (c) geographic variations; (d) genetic factors and evolution; (e) political/social conditions; and also (f) amount of plant material/space and manual labour needs. Copyright 2008 John Wiley & Sons, Ltd. [source]

Composition of essential oil, concrete, absolute, wax and headspace volatiles of Murrarya paniculata (Linn.) Jack flowers

P. K. Rout
Abstract Murraya paniculata (Linn) Jack, syn. M. exotica Linn., commonly known as orange jessamine, is grown in gardens for its large clusters of fragrant flowers. Distillation of the fresh flowers in water furnished the essential oil in 0.027% yield. Extraction of the fresh flowers with pentane afforded the concrete (0.78%). Precipitating the waxes from the concrete with methanol gave absolute (0.62%). The chemical composition of essential oil, concrete, absolute and wax were analysed by GC and GC,MS. The components of essential oil in significant amounts were , -elemene (1.4%), (E)-caryophyllene (3.6%), germacrene D (2.7%), (E)-nerolidol (25.7%), benzyl benzoate (8.1%), phenyl ethyl benzoate (8.0%) and manool (18.7%). The major components in the concrete and absolute, respectively, were phenyl ethyl alcohol (2.9%, 3.0%), indole (0.8%, 1.0%), (E)-nerolidol (6.5%, 7.0%), benzyl benzoate (5.0%, 6.5%), phenyl ethyl benzoate (8.0%, 8.6%) and manool (25.2%, 27.9%). The methanol-insoluble wax contained (E)-nerolidol (2.6%), manool (9.4%) and most of the fatty acids/esters. The composition of the volatile components in the headspace emitted by flowers still on the branch (live flowers) and also by the picked flowers was determined by HS,SPME on a PDMS fibre and these results are also presented. The major components found in the headspace were linalool, indole, (E)-caryophyllene, germacrene D, bicyclogermacrene and (E,E)- , -farnesene. Copyright 2007 John Wiley & Sons, Ltd. [source]

Volatile composition of the laksa plant (Polygonum hydropiper L.), a potential source of green note aroma compounds

J. Jiang
Abstract Volatile compounds were extracted from laksa plant (Polygonum hydropiper L.) by three isolation techniques,dynamic headspace sampling, simultaneous distillation and extraction (SDE) and liquid,liquid extraction with dichloromethane (DCM). In the GC,MS analysis of the volatile extracts, a total of 46 compounds were identi,ed, including 14 carbonyls, 14 alcohols, 10 hydrocarbons, four esters, two furans, one acid and one base. Carbonyls (aldehydes/ketones) and alcohols are the predominant classes of volatile compounds, accounting for almost 90% (or above) of the total volatiles extracted from the plant. The major compounds include dodecanal (3,40%), (E)-2-hexenal (20,35%), decanal (4,22%), (Z)-3-hexen-1-ol (4,31%), hexanal (1.7,5.1%) and , -caryophyllene (1.7,2.3%). Signi,cantly high levels of both (E)-2-hexenal (leaf aldehyde) and (Z)-3-hexen-1-ol (leaf alcohol) may make the weed plant become a potential source of green note aroma componds. More (Z)-3-hexen-1-ol was found in the stem while more (E)-2-hexenal was detected in the leaf. The laksa stem appeared to contain more decanal and dodecanal but less esters than the leaf. Different isolation techniques produced volatile extracts with different proportions of the major volatile components. Copyright 2005 John Wiley & Sons, Ltd. [source]

Supercritical carbon dioxide extraction of 2-acetyl-1-pyrroline and volatile components from pandan leaves

Natta Laohakunjit
Abstract The ,avour of pandan (Pandanus amaryllifolius Roxb.) leaves was extracted by supercritical ,uid with CO2 (SC-CO2) under different conditions of pressure, temperature and contact time to determine the yield of 2-acetyl-1-pyrroline (ACPY) and various other components; 14 volatile compounds on the gas chromatogram were identi,ed, and the predominant constituents were ACPY and 3-methyl-2(5H)-furanone. The interaction of different conditions signi,cantly in,uenced the yield of ACPY and various volatile compounds. There is a potential for high yield of ACPY by SC-CO2 at 200 bar, 500 C and 20 min. The SDE,ether extract was found to have a very small amount of ACPY and an undesirable odour, as compared to the dark green ethanol extract, which contains a relatively larger quantity of ACPY and even more 3-methyl-2(5H)-furanone. Although at least 34 new components were uncovered from SC-CO2, SDE, and ethanol extraction, both ACPY and 3-methyl-2(5H)-furanone were the components tentatively obtained by all three methods. Copyright 2004 John Wiley & Sons, Ltd. [source]

Quantitation of suspected allergens in fragrances (Part I): evaluation of comprehensive two-dimensional gas chromatography for quality control

Robert Shellie
Abstract An evaluation of comprehensive two-dimensional (2D) gas chromatography (GCGC) was performed to assess its suitability for the analysis of volatile fragrance components, recognized by the European Commission's Scienti,c Committee on Cosmetics and other Non-food Products (SCCNFP) as possible skin sensitizers. The 24 volatile components listed by the SCCNFP were baseline-resolved or better within one 30 min analysis. High-quality calibration data for standard mixtures were obtained, with R2 > 0.998 over the concentration range 2,1000 mg/l. However, the analysis of small spiked amounts of target compounds in truly complex fragrances was problematic, due to uncertainty in component assignment. The bene,ts and limitations of GCGC are reported, and a discussion of the proposed directions for the solution of this analysis is provided. Copyright 2004 John Wiley & Sons, Ltd. [source]

The Egyptian Eucalyptus camaldulensis var. brevirostris: chemical compositions of the fruit volatile oil and antioxidant activity

Ahmed H. El-Ghorab
Abstract The fruit volatile oil of E. camaldulensis var. brevirostris was isolated by hydrodistillation and thereafter the fruit marc was extracted by ethanol. The volatile oil obtained was subjected to analysis using gas chromatography,mass spectrometry. Thirty-eight volatile components were identified. The main volatile compounds in the fruit volatile oil were: aromadendrene (17.99%), ,-pinene (12.68%), p -cymenene (5.39%), ,-gurjunene (6.65%), cubenol (9.23%), thymol (1.62%) and p -cymen-7-ol (0.73%). The volatile components were classified into four groups: monoterpenes (20.6%), sesquiterpenes (33.8%), light-oxygenated (8.1%) and heavily-oxygenated (37.6%) compounds. The results showed that the concentration of sesquiterpenes and heavily-oxygenated compounds were higher than the other two classes. The main compound in the ethanol extract of fruit of E. camaldulensis was isolated by semi-preparative HPLC and identified as ellagic acid. The antioxidant activities of the fruits volatile oil and the ethanol extract as well as that of the tree bark were evaluated by the thiocyanate method. The ethanol extract of Eucalyptus fruit exhibited considerable activity compared with butylated hydroxyanisole (BHA) and tertiary butylated hydroquinone (TBHQ). The high inhibitory effect of the ethanol extract of fruit upon linoleic acid after 12 days might be related to the higher ellagic acid content. Copyright 2002 John Wiley & Sons, Ltd. [source]

Transfer of hydrocarbons from natural seeps to the water column and atmosphere

I. R. MacDonald
Abstract Results from surface geochemical prospecting, seismic exploration and satellite remote sensing have documented oil and gas seeps in marine basins around the world. Seeps are a dynamic component of the carbon cycle and can be important indicators for economically significant hydrocarbon deposits. The northern Gulf of Mexico contains hundreds of active seeps that can be studied experimentally with the use of submarines and Remotely Operated Vehicles (ROV). Hydrocarbon flux through surface sediments profoundly alters benthic ecology and seafloor geology at seeps. In water depths of 500,2000 m, rapid gas flux results in shallow, metastable deposits of gas hydrate, which reduce sediment porosity and affect seepage rates. This paper details the processes that occur during the final, brief transition , as oil and gas escape from the seafloor, rise through the water and dissolve, are consumed by microbial processes, or disperse into the atmosphere. The geology of the upper sediment column determines whether discharge is rapid and episodic, as occurs in mud volcanoes, or more gradual and steady, as occurs where the seep orifice is plugged with gas hydrate. In both cases, seep oil and gas appear to rise through the water in close proximity instead of separating. Chemical alteration of the oil is relatively minor during transit through the water column, but once at the sea surface its more volatile components rapidly evaporate. Gas bubbles rapidly dissolve as they rise, although observations suggest that oil coatings on the bubbles inhibit dissolution. At the sea surface, the floating oil forms slicks, detectable by remote sensing, whose origins are laterally within ,1000 m of the seafloor vent. This contradicts the much larger distance predicted if oil drops rise through a 500 m water column at an expected rate of ,0.01 m s,1 while subjected to lateral currents of ,0.2 m s,1 or greater. It indicates that oil rises with the gas bubbles at speeds of ,0.15 m s,1 all the way to the surface. [source]

Performance prediction of a refrigerating machine using R-407C: the effect of the circulating composition on system performance

P. Haberschill
Abstract This article presents a steady-state model of a vapour compression refrigerating machine using a ternary refrigerant mixture R-407C. When using a zeotropic mixture in a refrigerant cycle, the circulating composition does not agree with the composition of the original charged mixture. It is mainly due to the temperature glide and the vapour,liquid slip ratio. As a result of the composition shift and its magnitude, the system performance changes depending on the system design, especially the presence of liquid receiving vessels. In this paper, a method that predicts the circulating composition has been associated to a refrigerating machine model. The results obtained with this model show an enrichment in the most volatile components of about 1% for the circulating composition, which is sufficient to decrease the system performance by about 3%. Factors affecting the overall performance have been investigated. The results show a very strong performance dependence on the refrigerant charge. The COP can decrease by 25% when the refrigerant charge is insufficient. An initial charged composition variation of 2% involves variations of the cooling capacity of about 5%. Furthermore, our model was employed to compare the performance for both R-22 and R-407C. The cooling capacity for R-22 is slightly greater in comparison to R-407C and the COP is almost constant. Copyright 2002 John Wiley & Sons, Ltd. [source]

The Impact of Antioxidant Addition on Flavor of Cheddar and Mozzarella Whey and Cheddar Whey Protein Concentrate

I.W. Liaw
Abstract:, Lipid oxidation products are primary contributors to whey ingredient off-flavors. The objectives of this study were to evaluate the impact of antioxidant addition in prevention of flavor deterioration of fluid whey and spray-dried whey protein. Cheddar and Mozzarella cheeses were manufactured in triplicate. Fresh whey was collected, pasteurized, and defatted by centrifugal separation. Subsequently, 0.05% (w/w) ascorbic acid or 0.5% (w/w) whey protein hydrolysate (WPH) were added to the pasteurized whey. A control with no antioxidant addition was also evaluated. Wheys were stored at 3 C and evaluated after 0, 2, 4, 6, and 8 d. In a subsequent experiment, selected treatments were then incorporated into liquid Cheddar whey and processed into whey protein concentrate (WPC). Whey and WPC flavors were documented by descriptive sensory analysis, and volatile components were evaluated by solid phase micro-extraction with gas chromatography mass spectrometry. Cardboard flavors increased in fluid wheys with storage. Liquid wheys with ascorbic acid or WPH had lower cardboard flavor across storage compared to control whey. Lipid oxidation products, hexanal, heptanal, octanal, and nonanal increased in liquid whey during storage, but liquid whey with added ascorbic acid or WPH had lower concentrations of these products compared to untreated controls. Mozzarella liquid whey had lower flavor intensities than Cheddar whey initially and after refrigerated storage. WPC with added ascorbic acid or WPH had lower cardboard flavor and lower concentrations of pentanal, heptanal, and nonanal compared to control WPC. These results suggest that addition of an antioxidant to liquid whey prior to further processing may be beneficial to flavor of spray-dried whey protein. Practical Application:, Lipid oxidation products are primary contributors to whey ingredient off-flavors. Flavor plays a critical and limiting role in widespread use of dried whey ingredients, and enhanced understanding of flavor and flavor formation as well as methods to control or minimize flavor formation during processing are industrially relevant. The results from this study suggest that addition of an antioxidant to liquid whey prior to further processing may be beneficial to minimize flavor of spray-dried whey protein. [source]

Effect of Heat Treatment on Antioxidant Capacity and Flavor Volatiles of Mead

Carol L. Wintersteen
ABSTRACT: The objective of this study was to evaluate the effects of heat processing on the antioxidant capacity of mead (honey wine). Soy and buckwheat honey musts were subjected to 2 heat treatments and fermented into wine. Total phenolic concentration was determined. High-performance liquid chromatography (HPLC) phenolic profiling was performed on the methanol fraction of Amberlite extraction. Antioxidant capacity was evaluated using the oxygen radical absorbance capacity (ORAC) assay. Changes in volatile components were evaluated by headspace-solid phase microextraction/gas chromatography-mass spectrometry (H-SPME/GC-MS). ORAC values of experimental meads (3.62 mMTrolox equivalent) were comparable to those of commercial white wine (3.66 mMTrolox equivalent). No significant difference in antioxidant capacity due to heat treatment or honey type was observed. There was no difference in total phenolics between heat treatments in buckwheat mead; however, soy mead made from high-heated must had significantly greater phenolic concentration than the gently heated mead (,= 0.05). Linear regression analysis indicated a strong positive correlation between total phenolic concentration and antioxidant capacity by ORAC (r= 0.9077; P < 0.0001). HPLC analysis of phenolic profiles in the methanol fractions of Amberlite extraction of the meads indicated significantly higher levels of certain phenolics as a result of the high-heat process in buckwheat mead, but not in soy mead. Differences in volatile components that potentially impact flavor were noted between high and low heat treatments. Results of this study suggest dramatic heat treatments that are often avoided because their flavor impact in mead production have the potential to alter the antioxidant capacity of mead by changing phenolic profiles. [source]

Effect of Storage Time on Raw Sardine (Sardina pilchardus) Flavor and Aroma Quality

C. Prost
ABSTRACT: Qualitative and semi-relative quantitative changes in flavor profiles associated with the storage of raw sardine (Sardina pilchardus) were investigated. A sensory panel generated a list of 20 odorant descriptors of raw sardine. Forty-seven volatile components were identified by gas chromatography-mass spectrometry and were quantified by gas chromatography-flame ionization detector (GC-FID). Among them, 34 were highlighted as potent odorants using an olfactometric method. (E,E)-2,4-octadienal, E-2-penten-1-ol and 2,3-butanedione are the most potent odorants of raw sardine. The odor-active compounds responsible for oxidized flavors increased during storage, whereas sulfur-containing compounds associated with marine odors decreased. These results could be related to the increase in rancidity aroma and the decrease in marine/iodized aroma identified by the sensory panelists in stored raw fish. [source]

Representativeness of Apple Aroma Extract Obtained by Vacuum Hydrodistillation: Comparison of Two Concentration Techniques

E. Mehinagic
ABSTRACT: Vacuum hydrodistillation, which is a very gentle work-up procedure, has never been used for the extraction of apple aroma. During the concentration of aroma that follows vacuum hydrodistillation, some very volatile components can be lost. The aim of this study was to compare 2 different concentration techniques, liquid-liquid extraction and solid phase extraction, to obtain an apple aroma extract as close as possible to fresh apple. After the elimination of solvent from the extract by gas chromatography, the study of the odor characteristics of solvent-free extracts was made possible. Vacuum hydrodistillation was convenient for fresh apples. [source]

Enantiomeric composition studies in Lavandula species using supercritical fluids

Gema Flores
Abstract Characteristic aroma compounds in plants and essential oils of Lavandula from different varieties were examined. The study of the qualitative and quantitative composition of the major volatile components was faced by developing a method based on the use of supercritical fluid extraction-GC-MS (SFE-GC-MS). The optimization of a variety of parameters affecting SFE extraction enabled RSDs from three replicates lower than 2% to be achieved. Equally, recoveries of up to 59% were obtained by applying the proposed method. The use of multidimensional GC was necessary to enantiomerically resolve the target compounds. The obtained results showed enantiomeric purities >90% for all studied compounds in all varieties considered, proving the natural invariability of the enantiomeric composition of the compounds of interest. This information can be useful in authenticity studies as well as in selecting natural sources of enantiomerically pure compounds. [source]

Combination of GC-MS with local resolution for determining volatile components in si-wu decoction

Fan Gong
Abstract In this paper, the combination of gas chromatography-mass spectrometry with chemometric local resolution techniques such as subwindow factor analysis (SFA) and orthogonal projection resolution (OPR) is investigated as a method of determining volatile components present in a traditional Chinese medicinal formulation known as si-wu decoction and its two individual herbs Rhizoma chuanxiong and Radix angelicae sinensis. In order to validate the reliability of the results obtained, the volatile components of interest were further separated on open glass columns and then analyzed in the same way as above. With the help of SFA and OPR approaches, the purity of chromatographic peaks can first be identified. Then, the pure chromatogram and mass spectrum of each component involved in a target peak cluster can be easily resolved and subsequently subjected to similarity searches in the NIST MS database to qualitatively and quantitatively determine the volatile components. Our results showed that about 127, 80, and 97 chemical components could be separated and 81, 49, and 55 of them identified, representing 83.95%, 91.86%, and 85.11% of the total relative content of volatile components from Rhizoma chuanxiong, Radix angelicae sinensis, and si-wu decoction, respectively. The results obtained in this work strongly indicate that the combination of GC-MS with chemometric local resolution methods could greatly improve the chromatographic separation ability by means of mathematical approaches. Moreover, they indicated the reliability and practicability of this combined technique. [source]

Volatile components of raw and smoked black bream (Brama raii) and rainbow trout (Oncorhynchus mykiss) studied by means of solid phase microextraction and gas chromatography/mass spectrometry

Mara D Guilln
Abstract Solid phase microextraction followed by gas chromatography/mass spectrometry of raw and smoked black bream and rainbow trout was carried out. The volatile components of the raw fish belong to a limited number of groups of compounds. Raw black bream has a higher presence of acids than raw trout, while the latter contains more alcohols, hydrocarbons, esters and phenol derivatives; both contain similar concentrations of saturated aldehydes. The volatiles of the smoked fish basically comprise the compounds also detected in the raw fish together with others produced during the processing. Smoke components detected in both smoked fish species were mainly phenol, guaiacol and syringol derivatives, ketones, acetic acid and some polycyclic aromatic hydrocarbons. Smoked black bream contained a higher number and higher concentrations of smoke components than smoked rainbow trout. Large variations in concentrations of smoke components in the smoked fish samples indicated that the smoking process had not been totally homogeneous. The presence of autoxidatively derived compounds, such as unsaturated aldehydes, was mainly detected in some smoked bream samples, showing that this degradation process is not occurring homogeneously. The usefulness of the applied techniques for the study of volatile components of raw and smoked fish is shown. 2002 Society of Chemical Industry [source]

Zanthoxylum piperitum (DC), a potential feeding deterrent for mammals: studies with Microtus ochrogaster (Wagner)

Gisela Epple
Abstract Total extract from the fruit of Szechuan pepper (Zanthoxylum piperitum DC), the volatile components of the extract and a non-volatile fraction containing alkylamides (NVA fraction) are feeding deterrents for rats. The present study investigated the effectiveness of these natural repellents in prairie voles (Microtus ochrogaster Wagner). Two-choice feeding trials were conducted during which food-deprived voles were offered choices between oat-bran wafers. In Experiment 1, 10 voles were given three sets of feeding trials, each 2 h long. Baseline consumption was established during the first set of two trials by offering a choice between two oat-bran wafers dipped in ethanol, the control solvent. During the second set of two trials the voles were given a choice between an oat-bran wafer dipped in ethanol and a wafer dipped in Zanthoxylum extract. During the third set the voles were given a choice between a wafer served on top of a screened dish containing a sample of ethanol and a wafer served on top of a dish containing a sample of extract. In this manner the voles were exposed to volatile compounds emanating from the extract but could not contact it. Wafers dipped in extract were almost completely avoided. The volatile components of extract also significantly reduced food intake. In Experiment 2, habituation to the volatile constituents of extract was examined in 16 Zanthoxylum -nave voles. Baseline consumption was established by offering two wafers served on top of screened dishes containing ethanol. This was followed by twelve tests during which a choice between a wafer served above a sample of ethanol and a wafer served above a sample of extract was given. The voles failed to habituate to the volatile components of extract, consistently consuming less of the wafers served above extract. In Experiment 3 a dose-response curve to Zanthoxylum extract was established, using 12 stimulus-nave voles. After baseline consumption was established, the animals were given two tests each, presenting a choice between a control wafer and a wafer dipped in a dilution of extract (0.001,100 g liter,1). Only concentrations of 10 and 100 g liter,1 reduced food intake. In Experiment 4 the effects of the non-volatile fraction of extract were compared to those of whole extract. Vegetable oil was used as solvent. Eight stimulus-nave voles were given two tests with a choice between an oil-dipped and an extract-dipped wafer. A second group of eight voles received two tests with a choice between an oil-dipped and NVA-dipped wafer. Extract-dipped wafers were avoided, but the NVA fraction had no effect on food consumption. Copyright 2004 Society of Chemical Industry [source]

Chemical composition and antiproliferative activity of essential oil from the leaves of a medicinal herb, Schefflera heptaphylla

Yao-Lan Li
Abstract Schefflera heptaphylla (L.) Frodin is a medicinal herb widely used as a main ingredient of the popular health tea formulation against infections in Southern China. Twenty-seven volatile compounds were identified by GC-MS analysis from the essential oil obtained from the leaves of S. heptaphylla, and 17 of them belonged to monoterpenes or sesquiterpenes. The main volatile constituent in S. heptaphylla was found to be a monoterpene, , -pinene, comprising about 22% of the total volatile components. The essential oil showed significant antiproliferative activity against three cancer cell lines, MCF-7, A375 and HepG2 cells, with IC50 values of 7.3 g/mL, 7.5 g/mL and 6.9 g/mL, respectively. The result of the cytotoxicity assay indicates that (,)- , -pinene and (+)- , -pinene (commercially available from Sigma) also possessed antiproliferative activity against the cancer cells MCF-7, A375 and HepG2 with IC50 values ranging from 147.1 to 264.7 m. Copyright 2008 John Wiley & Sons, Ltd. [source]