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Headspace
Kinds of Headspace Terms modified by Headspace Selected AbstractsAn ecological cost of plant defence: attractiveness of bitter cucumber plants to natural enemies of herbivoresECOLOGY LETTERS, Issue 3 2002Anurag A. Agrawal Abstract Plants produce defences that act directly on herbivores and indirectly via the attraction of natural enemies of herbivores. We examined the pleiotropic effects of direct chemical defence production on indirect defence employing near-isogenic varieties of cucumber plants (Cucumis sativus) that differ qualitatively in the production of terpenoid cucurbitacins, the most bitter compounds known. In release,recapture experiments conducted in greenhouse common gardens, blind predatory mites were attracted to plants infested by herbivorous mites. Infested sweet plants (lacking cucurbitacins), however, attracted 37% more predatory mites than infested bitter plants (that produce constitutive and inducible cucurbitacins). Analysis of the headspace of plants revealed that production of cucurbitacins was genetically correlated with large increases in the qualitative and quantitative spectrum of volatile compounds produced by plants, including induced production of (E,)-,-ocimene (3E,)-4,8-dimethyl-1,3,7-nonatriene, (E,E)-,-farnesene, and methyl salicylate, all known to be attractants of predators. Nevertheless, plants that produced cucurbitacins were less attractive to predatory mites than plants that lacked cucurbitacins and predators were also half as fecund on these bitter plants. Thus, we provide novel evidence for an ecological trade-off between direct and indirect plant defence. This cost of defence is mediated by the effects of cucurbitacins on predator fecundity and potentially by the production of volatile compounds that may be repellent to predators. [source] Pump-free and low-cost negative pressure sampling device for rapid sample loading in MCEELECTROPHORESIS, Issue 24 2009Hongmei Hu Abstract A pump-free and low-cost negative pressure sampling device for injecting well-defined non-biased sample plugs into the separation channel of MCE was developed. It was composed of a pipet bulb, a 3-way electromagnetic valve and a single voltage supply at constant voltage. A sub-atmospheric pressure was created by hand-pressing air out of the pipet bulb and retained in it by switching the 3-way electromagnetic valve at cutoff position. During the sample loading stage, the sub-atmospheric pressure in the pipet bulb was applied via a 3-way electromagnetic valve to the headspace of the sealed sample waste reservoir (SW). A pinched sample plug was formed at the channel intersection in less than 0.5,s. Once the 3-way electromagnetic valve was switched to connect SW to ambient atmosphere to release the vacuum in SW, electrophoresis separation was consequently activated under the electric potentials applied. Experimental results demonstrated the pump-free negative pressure sampling device worked well in a wide vacuum degree ranged from ,250 to ,30,mbar with a satisfactory analytical precision. The sample consumption for each cycle was calculated to be 51,12,nL under the sampling pressure. Theoretical deduction indicates that the volume of the pipet bulb can be further reduced to 1,mL, which is critical for minimizing the sampling device for MCE. [source] Detecting active methanogenic populations on rice roots using stable isotope probingENVIRONMENTAL MICROBIOLOGY, Issue 3 2005Yahai Lu Summary Methane is formed on rice roots mainly by CO2 reduction. The present study aimed to identify the active methanogenic populations responsible for this process. Soil-free rice roots were incubated anaerobically under an atmosphere of H2/13CO2 or N2/13CO2 with phosphate or carbonate (marble) as buffer medium. Nucleic acids were extracted and fractionated by caesium trifluoroacetate equilibrium density gradient centrifugation after 16-day incubation. Community analyses were performed for gradient fractions using terminal restriction fragment polymorphism analysis (T-RFLP) and sequencing of the 16S rRNA genes. In addition, rRNA was extracted and analysed at different time points to trace the community change during the 16-day incubation. The Methanosarcinaceae and the yet-uncultured archaeal lineage Rice Cluster-I (RC-I) were predominant in the root incubations when carbonate buffer and N2 headspace were used. The analysis of [13C]DNA showed that the relative 16S rRNA gene abundance of RC-I increased whereas that of the Methanosarcinaceae decreased with increasing DNA buoyant density, indicating that members of RC-I were more active than the Methanosarcinaceae. However, an unexpected finding was that RC-I was suppressed in the presence of high H2 concentrations (80%, v/v), which during the early incubation period caused a lower CH4 production compared with that with N2 in the headspace. Eventually, however, CH4 production increased, probably because of the activity of Methanosarcinaceae, which became prevalent. Phosphate buffer appeared to inhibit the activity of the Methanosarcinaceae, resulting in lower CH4 production as compared with carbonate buffer. Under these conditions, Methanobacteriaceae were the prevalent methanogens. Our study suggests that the active methanogenic populations on rice roots change in correspondence to the presence of H2 (80%, v/v) and the type of buffer used in the system. [source] Subsurface addition emission modelENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 1 2005Allen Hatfield PhD Subsurface addition is commonly used in the chemical industry as a means of ensuring that the incoming reagent is distributed uniformly within a batch as the addition proceeds. The difference between subsurface addition and the typical above-surface addition is in how the inlet liquid stream enters the vessel. When calculating the process vent emissions for an above-surface addition one considers the partial pressure of the inlet stream components along with the batch components. This is because both mixtures have direct exposure to the vessel headspace during the addition process. For subsurface addition, volatile compounds that are contained in the inlet stream are exposed to the headspace only as they appear in the batch during the addition process. The purpose of this paper is to present a model for estimating the vent emissions for subsurface addition processes based on the integrated average liquid-phase composition. © 2004 American Institute of Chemical Engineers Environ Prog, 2004 [source] Volatile compounds of original African black and white shea butter from Tchad and CameroonEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 7 2006Sabine 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] Vents and seals in non-steady-state chambers used for measuring gas exchange between soil and the atmosphereEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 4 2001G. L. Hutchinson Summary Despite decades of research to define optimal chamber design and deployment protocol for measuring gas exchange between the Earth's surface and the atmosphere, controversy still surrounds the procedures for applying this method. Using a numerical simulation model we demonstrated that (i) all non-steady-state chambers should include a properly sized and properly located vent tube; (ii) even seemingly trivial leakiness of the seals between elements of a multiple-component chamber results in significant risk of measurement error; (iii) a leaking seal is a poor substitute for a properly designed vent tube, because the shorter path length through the seal supports much greater diffusive gas loss per unit of conductance to mass flow; (iv) the depth to which chamber walls must be inserted to minimize gas loss by lateral diffusion is smaller than is customary in fine-textured, wet or compact soil, but much larger than is customary in highly porous soils, and (v) repetitive sampling at the same location is not a major source of error when using non-steady-state chambers. Finally, we discuss problems associated with computing the flux of a gas from the non-linear increase in its concentration in the headspace of a non-steady-state chamber. [source] Odour-active compounds of Jinhua hamFLAVOUR AND FRAGRANCE JOURNAL, Issue 1 2008Huanlu Song Abstract Using DHS, SAFE, GC,O and GC,MS, the odour-active compounds of Jinhua ham were identified and ranked according their odour potencies. For DHS, the ham powder was purged with a nitrogen stream at a flow rate of 50 ml/min for 25 min, 5 min and 1 min, respectively. The effluent of sample headspace was trapped by a Tenax tube, which was placed onto the vessel for GC,O. The most important odorants (FD factor = 125) in Jinhua ham headspace were ethyl 2-methylbutanoate/ethyl 3-methylbutanoate, hexanal, 1-hexen-3-one, 1-octen-3-one, 2-acetyl-1-pyrroline and 2-methoxyphenol, followed by the following odorants (FD factor = 25): 3-methyl butanal, dimethyl trisulphide, 1-nonen-3-one, butanoic acid, phenylacetaldehyde, 3-methylbutanoic acid, 2-methyl(3-methyldithio)furan, , -nonalctone and 4-methylphenol (p -cresol). For SAFE, the ham powder was extracted with diethyl ether, distilled by SAFE and then separated into neutral/basic and acidic fractions. Both fractions were subjected to AEDA. The relatively high-odour impact compounds (Log3FD Factor ,5) of the N/B fraction of SAFE extract of Jinhua ham were 1-octen-one, ethyl 3-methylbutanoate, methional, phenylacetaldehyde, 2-phenylethanol, (E)-4,5-epoxy-(E)-decenal, p -cresol (4-methylphenol); 3-methylbutanal, hexanal, 2-acetyl-1-pyrroline, decanal, (E,Z)-2,6-nonadienal and (E,E)-decadienal. The important odorants of the Ac fraction of SAFE extract of Jinhua ham were butanoic acid, 3-methylbutanoic acid, hexanoic acid, phenylacetic acid and an unknown. It was shown that the aroma of Jinhua ham consisted of a variety of compounds having different odour properties; a single compound could not characterize the aroma of Jinhua ham. Copyright © 2008 John Wiley & Sons, Ltd. [source] Composition of essential oil, concrete, absolute, wax and headspace volatiles of Murrarya paniculata (Linn.) Jack flowersFLAVOUR AND FRAGRANCE JOURNAL, Issue 5 2007P. 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] 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] Ground Water Chlorinated Ethenes in Tree Trunks: Case Studies, Influence of Recharge, and Potential Degradation MechanismGROUND WATER MONITORING & REMEDIATION, Issue 3 2004Don A. Vroblesky Trichloroethene (TCE) was detected in cores of trees growing above TCE-contaminated ground at three sites: the Carswell Golf Course in Texas, Air Force Plant PJKS in Colorado, and Naval Weapons Station Charleston in South Carolina. This was true even when the depth to water was 7.9 m or when the contaminated aquifer was confined beneath ,3 m of clay. Additional ground water contaminants detected in the tree cores were cis,1,2-dichloroethene at two sites and tetrachloroethene at one site. Thus, tree coring can be a rapid and effective means of locating shallow subsurface chlorinated ethenes and possibly identifying zones of active TCE dechlorination. Tree cores collected over time were useful in identifying the onset of ground water contamination. Several factors affecting chlorinated ethene concentrations in tree cores were identified in this investigation. The factors include ground water chlorinated ethene concentrations and depth to ground water contamination. In addition, differing TCE concentrations around the trunk of some trees appear to be related to the roots deriving water from differing areas. Opportunistic uptake of infiltrating rainfall can dilute prerain TCE concentrations in the trunk. TCE concentrations in core headspace may differ among some tree species. In some trees, infestation of bacteria in decaying heartwood may provide a TCE dechlorination mechanism within the trunk. [source] Effects of CO2 absorbent and high-pressure treatment on the shelf-life of packaged Kimchi productsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 5 2003Joo W. Lee Summary The effects on extending the shelf-life of commercial Kimchi products and preventing pouch inflation by absorbing CO2 with calcium hydroxide, were compared with a treatment using high-hydrostatic pressure. The changes in the quality factors of Kimchi, such as CO2 accumulation in the headspace of the pouch, pH, total acidity and the microbial population of both total viable cells and lactic acid bacteria were measured during storage for 24 days at 10 °C. Pressurization at 400 and 600 MPa for 5 min at 20 °C were both effective in preventing inflation of the Kimchi pouches during storage at 10 °C, as was CO2 absorption at the level of 0.5 g CO2 absorbent per 80 g Kimchi. [source] Persistence effects in flavour release from liquids in the mouthINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 3 2003Kevin M. Wright Summary The flavour of drinks, creams and liquid-like food consumed without chewing is an important quality factor for consumers and manufacturers alike, so reliable predictive models of flavour release from liquids in the mouth are highly desirable. In this paper we show how the breath-by-breath concentration of aroma in the headspace after swallowing an aliquot of liquid can be modelled using basic principles of interfacial mass transfer. This mechanistic model is used to fit the experimental data for dilute aqueous solutions of five aroma compounds consumed by trained panellists. It is shown that many aroma compounds give detectable concentrations in the exhaled breath several minutes after swallowing and after ten or more exhalations. The influence of liquid composition on this aroma persistence effect is discussed. [source] Onion aphid (Neotoxoptera formosana) attractants, in the headspace of Allium fistulosum and A. tuberosum leavesJOURNAL OF APPLIED ENTOMOLOGY, Issue 1 2007M. Hori Abstract:, Attractancy of Allium fistulosum L. and Allium tuberosum Rottl. to adult apterae of the onion aphid, Neotoxoptera formosana (Takahashi), an oligophagous aphid pest of Allium crops, was investigated with a Y-tube olfactometer. The aphids were significantly attracted to both A. fistulosum and A. tuberosum. The headspace components of both plants were extracted with solid-phase microextraction (SPME) and analysed by gas chromatography-mass spectrometry (GC-MS). The main volatile components of A. fistulosum were dipropyl disulphide (relative contents: 67%), 1-propenyl propyl disulphide (23%) and dipropyl trisulphide (6%). In the headspace of A. tuberosum, diallyl disulphide was detected as the main component (58%). Attractancy of dipropyl disulphide, dipropyl trisulphide and diallyl disulphide to the aphids was examined with the Y-tube olfactometer. The aphids were significantly attracted to dipropyl trisulphide and diallyl disulphide at a concentration of 0.01%. Dipropyl disulphide did not significantly attract the aphids at any concentrations tested. It was revealed that attractancy of A. fistulosum and A. tuberosum was caused by dipropyl trisulphide and diallyl disulphide, respectively. The findings suggest that N. formosana uses these sulphur compounds, characteristic components of Allium plants, as olfactory cues to find the host plants. [source] HEAT TRANSFER TO CANNED PARTICULATES IN HIGH-VISCOSITY NEWTONIAN FLUIDS DURING AGITATION PROCESSINGJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 6 2006YANG MENG ABSTRACT Heat transfer to canned particulate-laden Newtonian high-viscous fluids (Nylon particles suspended in aqueous glycerin solution [40, 60, 80, 90 and 100%, v/v] and motor oil [85W140]) during end-over-end rotation was studied in a pilot-scale, full water-immersion single-cage rotary retort. Computations of conventional fluid-to-particle heat transfer coefficient (hfp) and overall heat transfer coefficient (U) were successful with multiple particles for an entire range of viscosity, but the predicted particle lethality was underestimated. With a single particle in the can, hfpand U calculations were successful only for low-viscosity fluids (40 and 60% glycerin solutions), but again resulted in underestimation of particle lethality. Apparent heat transfer coefficients (hap) between retort and particle surface and apparent overall heat transfer coefficient (Ua) were also evaluated, and this methodology worked well for all cases. Further, the particle lethality predicted using hap better matched the measured values. With a single particle in the can, the associated hap was significantly (P < 0.05) influenced by rotation speed, retort temperature, liquid viscosity, particle material and can size. Ua was significantly (P < 0.05) influenced by rotation speed and liquid viscosity. The effects of headspace, radius of rotation and particle size were not significant (P > 0.05) on hap and Ua values. [source] EFFECT OF ANTICAKING AGENT ADDITION AND HEADSPACE REDUCTION IN THE POWDERED-DRINK MIX SENSORY STABILITYJOURNAL OF FOOD QUALITY, Issue 3 2006INAR A. CASTRO ABSTRACT The objective of the present study was to assess the effect of the addition of 0.2% anticaking agent "silicon dioxide" (S) and of 70.0% reduction of the headspace in the package (H) both individually and combined (SH), on the sensory and physicochemical characteristics of a powdered-drink mix over a shelf-life period of 120 days. The "difference from control" test was applied to 10 trained panelists in order to assess the four treatments at 30-day intervals throughout the experimental period, according to visual aspect of the powdered mix and drink flavor. The results demonstrated that a reduction of 70% of the headspace was the most effective treatment for product sensory stability. Water activity (Aw) was a more sensitive parameter than moisture content and ascorbic acid degradation. Although Aw has shown a significant difference over time, the sensory properties still seemed to be a better shelf-life indicator for powdered mixes. Based on the sensory alterations of the aspect of the powder, a reduction of headspace and the limiting of shelf life to between 60 and 90 days could be recommended for powdered-drink mixes packaged in polypropylene containers. [source] EFFECT OF HEADSPACE OXYGEN AND FILMS OF DIFFERENT OXYGEN TRANSMISSION RATE ON TOXIN PRODUCTION BY CLOSTRIDIUM BOTULINUM TYPE E IN RAINBOW TROUT FILLETS STORED UNDER MODIFIED ATMOSPHERESJOURNAL OF FOOD SAFETY, Issue 3 2000ISABELLE DUFRESNE ABSTRACT Studies were conducted to determine the effect of various levels of headspace oxygen (0,100%, balance CO2) or film oxygen transmission rate (OTR) on the time to toxicity in modified atmosphere packaged (MAP) fresh trout fillets challenged with C. botulinum type E (102 spore/g) and stored under moderate temperature abuse conditions (12C). In all cases, trout were toxic within 5 days, irrespective of the initial levels of oxygen in the package headspace. However, spoilage preceded toxigenesis. Packaging of trout fillets in low gas barrier films, with OTRs ranging from 4,000 to 10,000 cc/m2/day at 24C and 0% relative humidity, also had no effect on time to toxicity in all MAP trout fillets. All fillets were toxic within 4,5 days and spoilage again preceded toxigenesis. This study has shown that the addition of headspace O2, either directly to a package or indirectly by using a low gas barrier film, had no influence on the time to toxigenesis or spoilage. Additional barriers, other than headspace O2 or film transmission rate, need to be considered to ensure the safety of MAP trout fillets, particularty at moderate temperature abuse conditions. [source] Effect of Milk on the Deodorization of Malodorous Breath after Garlic IngestionJOURNAL OF FOOD SCIENCE, Issue 6 2010Areerat Hansanugrum Abstract:, The effect of milk and milk components on the deodorization of diallyl disulfide (DADS), allyl methyl disulfide (AMDS), allyl mercaptan (AM), allyl methyl sulfide (AMS), and methyl mercaptan (MM) in the headspace of garlic as well as in the mouth- and nose-space after garlic ingestion was investigated using selected ion flow tube-mass spectrometry (SIFT-MS). Fat-free and whole milk significantly reduced the head-, mouth-, and nose-space concentrations of all volatiles. Water was the major component in milk responsible for the deodorization of volatiles. Due to its higher fat content, whole milk was more effective than fat-free milk in the deodorization of the more hydrophobic volatiles diallyl disulfide and allyl methyl disulfide. Milk was more effective than water and 10% sodium caseinate in the deodorization of allyl methyl sulfide, a persistent garlic odor, in the mouth after garlic ingestion. Addition of milk to garlic before ingestion had a higher deodorizing effect on the volatiles in the mouth than drinking milk after consuming garlic. Practical Application:, Ingesting beverages or foods with high water and/or fat content such as milk may help reduce the malodorous odor in breath after garlic ingestion and mask the garlic flavor during eating. To enhance the deodorizing effect, deodorant foods should be mixed with garlic before ingestion. [source] High Relative Humidity In-Package of Fresh-Cut Fruits and Vegetables: Advantage or Disadvantage Considering Microbiological Problems and Antimicrobial Delivering Systems?JOURNAL OF FOOD SCIENCE, Issue 4 2008J.F. Ayala-Zavala ABSTRACT:, This hypothesis article states that the high relative humidity (RH) of packaged fresh-cut fruits or vegetables that is associated with spoilage can be used as an advantageous way to deliver antimicrobial compounds using cyclodextrins (CDs) as carriers. CDs can function as antimicrobial delivery systems as they can release antioxidant and antimicrobial compounds (guest molecules) as the humidity levels increase in the headspace. Hydrophobic antimicrobial guests can be complexed with CDs due to the amphiphatic nature of the host. Then, at high RH values, due to the water,CDs interaction, host,guest interactions are weakened; consequently, the antimicrobial molecule is released and should protect the product against the microbial growth. Potential antimicrobial compounds capable of forming complexes with CDs are discussed, as well as possible applications to preserve fresh-cut produce and future research in this area. [source] Effects of Mild Heat Treatment on Microbial Growth and Product Quality of Packaged Fresh-Cut Table GrapesJOURNAL OF FOOD SCIENCE, Issue 8 2007L. Kou ABSTRACT:, The changes in packaged fresh-cut grape quality and microbial growth as affected by mild heat treatments and the retention of grape cap stems during 5 °C storage were evaluated. Each individual grape was either manually pulled off (stemless) from the stems, or cut (cut stem) to allow for a 1- to 2-mm cap stem remaining on the berry. The samples were sanitized in 100 mg/L chlorine solution for 1 min, followed by a mild heat treatment in a water bath (45 °C, 8 min) or an oven (55 °C, 5 min). After cooling, the berries were packaged in rigid trays sealed with a gas permeable film and stored at 5 °C. Product quality and decay rate were evaluated periodically during storage. The results indicate that in the package headspace for hot water treatment of stemless grapes, partial pressures of O2 declined significantly (P < 0.05) less and C2H4 increased significantly (P < 0.001) less than for the control and hot air treatment. Stem removal and heat treatment had significant (P < 0.05) effects on the decay rate of grapes during storage. Hot water treatment maintained a significantly lower decay rate than the control and hot air treatment throughout the entire storage. Color and texture were not significantly (P > 0.05) affected by either heat treatment or stem removal. Grapes that retained the cap stems and received hot water treatment had the lowest decay rate and lowest microbial growth with the absence of any negative impact on grape color, texture, and flavor. [source] Electronic 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] Decomposition and Transformation of Aroma Compounds and Anthocyanins during Black Currant (Ribes nigrum L.) Juice ProcessinJOURNAL OF FOOD SCIENCE, Issue 9 2002B.B. Mikkelsen ABSTRACT: Processing of black currant juice includes crushing, heating, enzyme treatment, pressing, pasteurization, clarification, and filtration. Changes in concentration of impact aroma compounds and anthocyanins during black currant juice processing in pilot plant scale were examined. Impact compounds were identified by gas chromatography-olfactometry and quantified by dynamic headspace and gas chromatography-mass spectrometer. Anthocyanins were analyzed by the pH-differential method. Identified aroma compounds comprised volatiles like esters, terpenes, terpenoids, and ketones. The reduction of aroma compounds and anthocyanins during the process was approximately 50 to 100% and 25%, respectively. The pressing step definitely had a negative effect on the concentration of aroma compounds and anthocyanins, and the heating treatments were mainly negative as well. [source] The Stability of Collected Human Scent Under Various Environmental Conditions,JOURNAL OF FORENSIC SCIENCES, Issue 6 2009Davia T. Hudson Ph.D. Abstract:, Human scent evidence collected from objects at a crime scene is used for scent discrimination with specially trained canines. Storage of the scent evidence is usually required yet no optimized storage protocol has been determined. Storage containers including glass, polyethylene, and aluminized pouches were evaluated to determine the optimal medium for storing human scent evidence of which glass was determined to be the optimal storage matrix. Hand odor samples were collected on three different sorbent materials, sealed in glass vials and subjected to different storage environments including room temperature, ,80°C conditions, dark storage, and UVA/UVB light exposure over a 7-week period. Volatile organic compounds (VOCs) in the headspace of the samples were extracted and identified using solid-phase micro-extraction,gas chromatography/mass spectrometry (SPME,GC/MS). Three-dimensional covariance mapping showed that glass containers subjected to minimal UVA/UVB light exposure provide the most stable environment for stored human scent samples. [source] Performance Evaluation of the Scent Transfer UnitÔ (STU-100) for Organic Compound Collection and ReleaseJOURNAL OF FORENSIC SCIENCES, Issue 4 2006Brian A. Eckenrode Ph.D. ABSTRACT: The Scent Transfer UnitÔ (STU-100) is a portable vacuum that uses airflow through a sterile gauze pad to capture a volatiles profile over evidentiary items for subsequent canine presentation to assist law enforcement personnel. This device was evaluated to determine its ability to trap and release organic compounds at ambient temperature under controlled laboratory conditions. Gas chromatography-mass spectrometry (GC-MS) analyses using a five-component volatiles mixture in methanol injected directly into a capture pad indicated that compound release could be detected initially and 3 days after the time of collection. Additionally, 15 compounds of a 39-component toxic organic gaseous mixture (10,1000 parts per billion by volume [p.p.b.v]) were trapped, released, and detected in the headspace of a volatiles capture pad after being exposed to this mixture using the STU-100 with analysis via GC-MS. Component release efficiencies at ambient temperature varied with the analyte; however, typical values of c. 10% were obtained. Desorption at elevated temperatures of reported human odor/scent chemicals and colognes trapped by the STU-100 pads was measured and indicated that the STU-100 has a significant trapping efficiency at ambient temperature. Multivariate statistical analysis of subsequent mass spectral patterns was also performed. [source] Determination of polycyclic aromatic hydrocarbons in olive oil by a completely automated headspace technique coupled to gas chromatography-mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2006Francisco J. Arrebola Abstract A new and completely automated method for the determination of ten relevant polycyclic aromatic hydrocarbons (PAHs) in olive oil is proposed using an extraction by the headspace (HS) technique. Quantification and confirmation steps are carried out by gas chromatography-mass spectrometry (GC-MS) combining simultaneously selected-ion monitoring (SIM) and tandem mass spectrometry (MS/MS). This combination offers on one hand an increased sensitivity and on the other hand, selective and reliable qualitative information. Sample pretreatment or clean-up are not necessary because the olive oil sample is put directly into an HS vial, automatically processed by HS and introduced into the GC-MS instrument for analysis. Because of its high selectivity and sensitivity, a triple-quadrupole (QqQ) detector coupled with the gas chromatograph allows us to limit handling. Each sample is completely processed in approximately 63 min (45 min for HS isolation and 18 min for GC-MS determination), a reduced time compared with previously published methods. The chemical and instrumental variables were preliminarily optimized using uncontaminated olive oil samples spiked with 25 µg kg,1 of each target compound. The final method was validated to ensure the quality of the results. The precision was satisfactory, with relative standard deviation (RSD) values in the range 3,9%. Recovery rates ranged from 96 to 99%. Limits of detection (LOD) were calculated as 0.02,0.06 µg kg,1 and the limits of quantification (LOQ) were obtained as 0.07,0.26 µg kg,1. It must be mentioned that the LOD and LOQ are much lower than the maximum levels established by the European Union (EU) in oils and fats intended for direct human consumption or for use as an ingredient in foods, which are set at 2 µg kg,1. All the figures of merit are completely in accordance with the latest EU legislation. This fact makes it possible to consider the proposed method as a useful tool for the control of PAHs in olive oils. Copyright © 2006 John Wiley & Sons, Ltd. [source] Perfumery quaternary diagrams for engineering perfumesAICHE JOURNAL, Issue 8 2009Miguel A. Teixeira Abstract The Perfumery Ternary Diagram (PTD®) methodology predicts the headspace odor character and intensity of fragrant mixtures, applying the concept of odor value (OV) to multi-component systems. This methodology is extended here to quaternary and quinary odorant systems through the use of tetrahedric diagrams. To present this new methodology, the effect of different base notes in quaternary systems of the type (limonene + geraniol + base note + ethanol) and its forming ternary subsystems has been studied. Base notes selected were: vanillin, tonalide, ambrox, and galaxolide. The Perfumery Quaternary Diagrams (PQD) of the mixtures studied show the different headspace odor character, with ambrox and galaxolide dominating most of the composition spectrum (OVmax). The methodology was also applied to the quinary mixture (limonene + geraniol + vanillin + tonalide + ethanol), and the effect of different concentrations of tonalide on the headspace is presented. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] A new methodology for the definition of odor zones in perfumery ternary diagramsAICHE JOURNAL, Issue 8 2006Vera G. Mata Abstract The new methodology called "Perfumery Ternary Diagram" helps perfumers in odor prediction, allowing a fast evaluation of the odor value in the headspace for all possible combinations of a non-ideal perfume liquid mixture with three fragrant components and one or more solvents. In this work, the determination of Perfumery Ternary Points (PTP) and Perfumery Binary Lines (PBL) is described, allowing a complete definition of Perfumery Ternary Diagram (PTD) odor zones, without the need to calculate a large number of points inside the triangle region. The methodology of PTP and PBL determination was applied to the system: limonene, geraniol, vanillin, and ethanol. The effect of solvent,ethanol,on the odor zones, namely on the number of PTP and on the shape of the PBL was studied, as well as the effect of the non-idealities. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] INFLUENCE OF GLASS SHAPE ON WINE AROMAJOURNAL OF SENSORY STUDIES, Issue 1 2002J.F. DELWICHE ABSTRACT Differences in the physical shape of glasses could potentially influence proportions of aromatic compounds trapped in the headspace of a wine glass, altering the perception of a wine. Blindfolded, naïve subjects assessed the aroma of a California Cabernet Sauvignon presented in 4 different glasses. Two of these were from a speciality line of crystal wine glasses, one designed for Chardonnay, the other for Bordeaux/Cabernet Sauvignon. A restaurant-style wine glass and a leaded crystal goblet were the remaining vessels used. The nonexpert judges assessed wine aroma for total intensity, fruitiness, vinegariness, oakiness, and mustiness, as well as liking. The only significant difference found in the aroma intensity ratings was for the Bordeaux glass, which was rated as having a significantly lower total intensity than the other three glasses. However, several significant correlations were found between the attribute intensity ratings and physical characteristics of the glasses. This suggests that the glass does have a limited, but subtle, impact upon the olfactory experience of wines. [source] Application of solid phase microextraction for the determination of soil fumigants in water and soil samplesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 1 2005Sonia Fuster Abstract The potential of solid phase microextraction (SPME) for the determination of the soil fumigants 1,3-dichloropropene (1,3-DCP) and methyl isothiocyanate (MITC) in environmental samples such as soil and water samples has been investigated. Direct immersion SPME followed by GC/ECD/NPD analysis allowed the rapid determination of the two fumigants in water samples, with very little sample manipulation, giving an LOD of 0.5 ,g L,1. Precision, calculated as relative standard deviation (RSD) for six replicates at three concentration levels, was found to be lower than 20% at the concentration levels tested. For the analysis of soil samples, headspace (HS)-SPME combined with GC/ECD/NPD analysis has been applied. Quantification using matrix-matched calibration curves allowed determination of both analytes (MITC and 1-3-DCP) with a LOD of 0.1 ,g kg,1 (RSD <10%) for the two concentration levels assayed (0.02 and 0.2 mg kg,1). The HS-SPME procedure developed in this paper was applied to soil samples from experimental green house plots treated with metham-Na, a soil disinfestation agent that decomposes in soil to MITC. The absence of sample manipulation as well as the low solvent consumption in SPME methodology are among the main advantages of this analytical approach. [source] Monitoring of Emulsion Polymerisation Processes using Ion Mobility Spectrometry,A Pilot StudyMACROMOLECULAR REACTION ENGINEERING, Issue 2-3 2009Wolfgang Vautz Abstract Online monitoring of monomer concentrations in (semi-) batch emulsion polymerisation reactors is important for safe and cost-efficient operation of production plants. In the present pilot study, ion mobility spectrometry was applied for monitoring the concentration during emulsion polymerisation of vinyl acetate (VA) using UV light for ionisation of the headspace of a continuous sample flow. Satisfactory sensitivity for online process monitoring of the monomer concentration in the reactor was observed (LOD 400 ng,·,L,1 air, equivalent to <1%). Furthermore, it is possible to discriminate between VA and other common monomers [butyl acrylate (BA), methyl methacrylate (MMA)]. Using the more efficient , -radiation ionisation, monomer concentration could be measured even in the final latex as a measure of the final product properties. [source] Modelling a modified atmosphere packaging system for fresh scallops (Argopecten purpuratus)PACKAGING TECHNOLOGY AND SCIENCE, Issue 2 2007R. Simpson Abstract Seafood is a highly perishable food, which has a relative short shelf-life. Modified atmosphere packaging (MAP) is a system that offers a way of extending the shelf-life of seafood products, maintaining quality and inhibiting bacterial growth. The objective of this research was to study and determine the optimal conditions for packaging scallops in a modified atmosphere system, which includes CO2/O2/N2 mixture, headspace:food ratio and storage temperature, utilizing an integrated mathematical model for MAP systems with its respective experimental validation. For validation purposes, two experiments were conducted, using gas mixtures of: (a) 45% CO2/10% O2/45% N2; and (b) 60% CO2/10% O2/30% N2. In addition, two experiments, at 6°C and 20°C, were conducted to obtain the shelf-life model, utilizing the following gas mixtures: 30% CO2/10% O2/60% N2; 45% CO2/10% O2/45% N2; 60% CO2/10% O2/30% N2; and 75% CO2/10% O2/15% N2. Gas mixtures with CO2 concentrations between 30% and 70% and different headspace:food ratios were tested during simulations. The optimal conditions for scallop storage were a 60% CO2/10% O2/30% N2 gas mixture and a headspace:food ratio of 2:1. With these conditions, a simulated shelf-life of 21 days was obtained. Optimal conditions consider maximum shelf-life, an adequate film collapse criterion, and time to reach the pseudo-equilibrium condition. The predictive mathematical model, coupled with experimental studies for specific products, can be efficiently utilized to evaluate packaging alternatives (size, material and selected thickness) for different temperatures and initial gas concentration scenarios of MAP products. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||||||||||||||