Dissertations / Theses on the topic 'Volatile compounds'

Polycyclic aromatic hydrocarbons (PAHs) are an important class of volatile organic compounds (VOCs) which pose enormous health and environmental threats. This thesis investigates different catalyst formulations for the complete oxidation of naphthalene (Np). a model PAH. Low loadings of vanadium added during the impregnation step of catalyst preparation were found to enhance the naphthalene oxidation activity of Pd-alumina and Pt- alumina catalysts while higher loadings were detrimental to the catalysts' performance. The promotional effect has been attributed to the presence of a low concentration of a particular type of vanadium species which fosters the redox behaviour of the binary system (Pd/V or Pt/V) coupled with the change in the active metal (Pd or Pt) particle size (Pd or Pt dispersion). The presence of high concentrations of crystalline V2O5 species has been suggested to account for the lower activity observed for Pd/V and Pt/V catalysts with vanadium loadings in the range of 6 - 12% and 1 - 12 % respectively. It is postulated that the mechanism of naphthalene oxidation over Pd/V differs from the mechanism of oxidation over Pt/V catalysts. The nature of support material was established to be crucial for the activity of Pt- supported catalysts for naphthalene oxidation. The Pt dispersion, metal-support interaction (MSI) and oxidation state of Pt varied as a function of the nature of support and hence resulted in differences in the Np oxidation efficiency of five Pt- supported catalysts with equal Pt loading but different supports. Low Pt dispersion (high Pt particle size), weak MSI and metallic state of Pt favoured Np oxidation. Si02 proved to be the best amongst five Pt supports investigated for Np oxidation. A variation in the preparation method and preparation conditions of ceria affected the surface area, crystallite size, oxygen defect concentration, morphology and surface reducibility of the ceria catalyst and hence the Np oxidation activity. High surface area, small crystallite size, and high oxygen defect concentration of Ce02 favoured the activity of the catalyst for Np oxidation. The best preparation methods in this study were found to be homogeneous precipitation with urea (UR) and precipitation with the carbonate (CR). Optimum preparation conditions for ceria (UR) were established and a highly active nano-crystalline ceria catalyst for Np oxidation was derived. The addition of low and high loadings of Pt during the precipitation of this ceria (UR) catalyst resulted in less active naphthalene oxidation catalysts. The drop in activity of ceria with Pt doping has been attributed to a strong metal support interaction between Pt and ceria which limits the ease at which lattice oxygen is consumed in the Mars-Van krevelen redox cycle.

Abstract This thesis describes efforts made on the development of an existing catalytic incinerator. The development work, called process characterization, consists of four general parts. These are the development of measurement methodology, the studying of construction materials, the selection of suitable catalysts and the testing of the effects of process operation conditions. The two application areas for catalytic incineration considered in this thesis are solvent emission abatement (VOC, volatile organic compounds) and chip bin emission abatement (SVOC, sulphur-containing volatile organic compounds). As a baseline, the process characterization is started with the development of measurement methodology. In general, the methodology will decrease costs and simplify the carrying out of the actual measurements and thereby make the measurement time more effective. In the methodology it is proposed that continuous total concentration measurement should be used in connection with qualitative sampling to obtain reliable measurement data. The selection of suitable construction materials for the application is very important. As shown in this thesis, the end conversions in solvent emission abatement may even be improved through the selection of the proper construction materials. In chip bin emission abatement, the problem arises from corrosive oxidation products that set limits on the construction materials used as well as on oxidation conditions. Catalyst selection is based on the following catalytic properties: activity, selectivity and durability. These catalytic properties are studied either at the laboratory or on an industrial scale. The catalytic materials tested are Pt, Pd, Pt-Pd, Cu-Mn oxides, MnO2-MgO, CuxMg(1-x)Cr2O4 and CuxCr2O4. The most important selection criteria in solvent emission abatement are proposed to be activity and selectivity. In the case of chip bin-SVOC-abatement, these are selectivity and durability. Based on these criteria, catalysts containing Cu-Mn oxides and Pt were demonstrated to be the best catalysts in VOC oxidation, and catalyst containing MnO2-MgO was shown to be best catalyst in SVOC oxidation. A study on the effect of process operation parameters (temperature, concentration and gas hourly space velocity (GHSV)) and moisture was carried out with the aid of factorial design. In VOC (n-butyl acetate) oxidation, the most influential process parameter was GHSV, which decreased the end conversion when it was increased. In SVOC (DMDS) oxidation, the effect of temperature was most significant. The end conversions increased as the temperature increased. Moisture slightly decreased the formation of by-products in n-butyl acetate oxidation. In DMDS oxidation, moisture slightly increased the end conversions at a lower temperature level (300°C). At the end of the thesis, these process parameters are also discussed from the standpoint of the catalysts' activity, selectivity and durability. Finally, proposals for process improvements are suggested.

The central aim of this thesis is to support the efforts to counteract certain environmental problems caused by emissions of volatile organic compounds. The purpose of this work was (1) to develop a method to establish the amount of emitted substances from dryers, (2) to determine the effect of drying medium temperature and end moisture content of the processed material on emissions of monoterpenes and other hydrocarbons, (3) to examine the emissions of monoterpenes during production of pellets, and (4) to examine the natural emissions from forests with an eye to implications for modelling. The measurement method (1) resolves the difficulties caused by diffuse emissions, and also solves the problems associated with high moisture content of the drying medium. The basic idea is to use water vapour to determine the exhaust flow, while a dry ice trap is used both to preconcentrate emitted volatile organic compounds and to determine the moisture content of the drying medium. The method as used in this paper has an uncertainty of 13% using a 95% confidence interval. Emissions from a spouted bed (2) in continuous operation drying Norway spruce sawdust at temperatures of 140°C, 170°C or 200°C was analysed with FID and GC-MS. When the sawdust end moisture content was reduced below 10%wb, emissions of terpenes and volatile organic compounds per oven dry weight increased rapidly. Increased temperature of the drying medium increased the amounts of emitted monoterpenes when sawdust moisture content was below the fibre saturation point. Examination of sawdust and wood pellets from different pellets producers (3) revealed that most of the terpene emissions happened during the drying step, with rotary dryers causing higher emissions than steam dryers. Almost all of the volatile terpenes remaining in wood after drying were released during pelleting. When sawdust with higher moisture content was used in the pellets press, the terpene emissions were increased. Terpenes emitted naturally from vegetation can have an adverse environmental impact. Factors affecting terpene emissions from tree species in Sweden were reviewed (4). Models for prediction of terpene fluxes should include not only temperature but also light intensity, seasonal variation, and a base level of herbivory and insect predation. Prediction of high concentrations of ambient terpenes demand sufficient resolution to capture emission peaks e.g. those caused by bud break.

Les composés organiques volatils oxygénés (COVO), principalement émis par des sources biogènes, jouent un rôle majeur dans la chimie de l'atmosphère, le changement climatique, l'environnement et la santé. Il a été récemment démontré que ces émissions augmentent en cas de stress biotique et/ou abiotique. Les COVO biogéniques peuvent subir une variété de réactions, tant chimiques que photolytiques, et ils sont impliqués dans la formation d'Aérosols Organiques Secondaires (AOS). Ces composés ont été détectés dans diverses régions, mais il y a très peu d’informations sur leurs processus de dégradation sous conditions troposphériques. La compréhension des mécanismes d'oxydation de ces espèces est d'un intérêt fondamental et fournit des données cruciales pour les modèles atmosphériques qui sont utilisés par les responsables politiques pour formuler et décider des stratégies d'amélioration de la qualité de l'air. Cette thèse vise à améliorer les connaissances actuelles sur le comportement de ces COVO, pour une meilleure compréhension de leur impact sur la chimie atmosphérique. Dans ce travail, nous avons présenté une étude détaillée de la dégradation atmosphérique des aldéhydes insaturés en C5-C7 et des alcools insaturés en C5-C8 par ozone, l’atome Cl et le radical OH. Les principaux objectifs étaient de mieux comprendre le mécanisme de réaction et de mettre en évidence leur potentiel à former des AOS. Pour atteindre ces objectifs, nous nous sommes concentrés sur quatres volets : (i) détermination du spectre IR et UV des aldéhydes insaturés en C5-C7, (ii) détermination de la constante de vitesse pour les systèmes COVO + Oxydant étudiés à température ambiante, (iii) identification et quantification des produits en phase gazeuse, (iv) détermination des rendements en AOS. Les études sur les produits ont été menées avec et sans ajout d'un piégeur des radicaux OH. Les expériences ont été réalisées dans huit réacteurs différents, statiques (chambres) ou dynamiques (flux), et diverses techniques analytiques ont été utilisées pour étudier les produits de réaction (FTIR, GC-FID/MS, SPME-GC/MS, HPLC, PTR-ToF-MS, SIFT-MS, PLP-LIF) et la formation de SOA (SMPS, FMPS)
Oxygenated Volatile Organic Compounds (OVOCs), mainly released from biogenic sources, play a major role in atmospheric chemistry, climate change, environment, and health. These emissions have been recently shown to increase in the case of biotic and/or abiotic stresses. Biogenic OVOCs may undergo a wide variety of reactions, both chemical and photolytic, and they contribute in the formation of Secondary Organic Aerosols (SOAs). These compounds have been detected in various areas, but little is known about their degradation processes under tropospheric conditions. Understanding the oxidation mechanisms of these species is of fundamental interest and yields crucial data for atmospheric models used by policymakers in formulating and deciding strategies for improving air quality. This dissertation aims to improve the current knowledge of those OVOCs behaviors to better understand their impact on atmospheric chemistry. This work reports a detailed study of the atmospheric degradation of C5-C7 unsaturated aldehydes and C5-C8 unsaturated alcohols by ozone, Cl atom, and OH radical. The main objectives were to better understand the reaction mechanism and to feature the SOA formation potential. To achieve these objectives, we focused on four topics: (i) determination of IR and UV spectrum of C5-C7 unsaturated aldehydes, (ii) determination of the rate constant for the studied OVOCs + Oxidant at room temperature, (iii) identification and quantification of the gas-phase products, (iv) determination of the SOA yields. The product studies were investigated both with and without adding an OH radical scavenger. Experiments were performed in eight different static (chambers) or dynamic (flow) reactors, and various analytical techniques were used to investigate the reaction products (FTIR, GC-FID/MS, SPME-GC/MS, HPLC, PTR-ToF-MS, SIFT-MS, PLP-LIF) and SOA formation (SMPS, FMPS)

Vine tea (Ampelopsis grossedentata) is a Chinese herbal tea, rich in the natural antioxidant dihydromyricetin, that has multiple health properties and potential food and beverage applications. However, there is little information available on vine tea aroma, color and sensory characteristics. In this study, volatile components of vine tea infusions were identified by headspace solid-phase micro-extraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS). Commercial vine teas samples were brewed with distilled water and Blacksburg (VA, USA) tap water and analyzed in triplicate. Vine tea infusions had acidic pH values and dark, reddish-yellow color. Type of water and vine tea sample both affected the overall volatile chemical composition of vine tea infusions. A total of fifty-six volatile components were identified in vine tea infusions. However, only seven aldehydes (hexanal, (E)-2-hexenal, (Z)-4-heptenal, nonanal, (E,Z)-2,4-heptadienal, (E,E)-2,4-heptadienal, and β-cyclocitral), two ketones (6-methyl-5-hepten-2-one and β-ionone), and one alcohol (1-penten-3-ol) were identified in more than 90% of all vine tea infusions (n=54). Results of this study may help further investigations in chemical and sensorial characteristics of vine tea, and the development of new healthy products.
Master of Science in Life Sciences

Aerosols are either emitted directly into the atmosphere or are generated in the atmosphere; the latter process forms secondary organic aerosol (SOA). One of the important sources for SOA is the oxidation of volatile organic compounds (VOCs) by OH radicals, NOx, and O3. Aerosol can be visualized as suspended solid or liquid particle which is in equilibrium with surrounding gases. The products of SOA formation is a mixture of semi volatile organic compounds and a fraction of the products are condensable under atmospheric conditions. The condensable portion of aerosol is called particulate matter (PM) and these suspended particles can range in diameter from a few nanometers to microns. PM can impact climate through direct and indirect radiative forcing and can degrade air quality by reducing visibility and causing detrimental health effects. SOA can also form indoors, which also contributes to the health risk of PM. The severe impact of PM on human health and climate drives the scientific community to investigate the volatile organic compounds (VOCs) and their potential to form SOA, as well as the factors that alter the efficiency of SOA generation and the type of products. In a similar pursuit, the focus of this dissertation is the investigation of the SOA precursors that are emitted from trees and how they vary as a function of insect infestation. Also, the role of mixtures of VOCs as SOA precursors are investigated; commercial and lab made VOC mixtures are studied for SOA generation, product analysis, and absorption characteristics of aged SOA. Chapter 1 introduces PM, VOCs present in atmosphere, SOA generation, and speciation of products generated from the ozonolysis of VOCs. The impact of PM on human health and climate are summarized. A literature survey on the VOCs that are precursors to SOA and present in the outdoor and indoor environment is presented along with factors that may lead to variability in amount of VOCs. SOA generation from direct plant emissions and consumer products is surveyed. These studies show that VOC oxidation generate SOA which is important in the atmosphere due to climate and health effects and indoors due to health effects. A summary of SOA phase partitioning theories, the reaction mechanism for the formation of products from ozonolysis of the dominant biogenic SOA precursors (monoterpenes), and the factors that affect SOA generation is presented. Chapter 2 summarizes the results obtained from a field study assessing the impact of bark beetle infestation on SOA precursor emissions from forests in the Western United States. Samples of VOCs were collected by our collaborators from healthy and bark beetle infested trees using scent traps. We solvent extracted and analyzed by gas chromatography/mass spectrometry (GC/MS) nearly four hundred scent traps. An increase in the total and the individual VOCs emitted by infested trees was measured. A statistical analysis shows significant differences between the emissions from infested and healthy trees. A perspective is provided on potential impact of bark beetle infestation on regional SOA. The majority of the laboratory experiments for SOA generation have focused on individual VOCs as the single SOA precursor. However, as demonstrated in Chapter 2 for example, in a real environment multiple VOCs co-exist. Multiple SOA precursors undergo concurrent oxidation reactions, and it is not known if the products from concurrent oxidation of multiple precursors are the same as the sum of the products from individual SOA precursors. Mass closure analysis of field samples show that a significant fraction of the chemical identity of organic PM is unknown, but the chemistry impacts the toxicity of PM. Hence, it is important to understand SOA formation from realistic SOA mixtures. Chapter 3 describes the results of the SOA generation by ozonolysis of limonene and VOC mixtures containing limonene. We use an additive approach for building a surrogate VOC mixture close in composition to a commercially-available mixture. The yield of PM as a function of VOC precursor mixture was measured with respect to VOC composition using smog chamber SOA generation and scanning mobility particle sizing. PM in the chamber was collected onto filters and extracted, and the individual products of SOA were identified and quantified by GC/MS. The condensed-phase SOA products generated during these experiments for different VOC mixtures are compared. In Chapter 4, condensed-phase products sampled from SOA generated by the ozonolysis of α pinene and VOC mixtures containing α pinene, including two fir needle essential oils, are studied by extracting filter samples and analyzing the extracts by GC/MS. The products generated from VOC mixtures are characteristic of the most dominant VOC present in the mixture i.e. either limonene or α pinene. Some mixtures show the generation of new products which are not observed for corresponding individual VOC ozonolysis and hence can be used as marker for the corresponding VOC mixture. The distribution of α-pinene SOA products changes as the composition of the SOA precursor mixture changes. In Chapter 5, the UV visible absorption characteristics of ammonium ion aged SOA are discussed. Ammonium ion aging of aerosol leads impacts the radiative properties of aerosol and has the potential to impact aerosol's role in climate change. Filter samples containing SOA generated from two mixtures with different dominant monoterpenes (α-pinene-based Siberian fir needle oil and a limonene-based air freshener) were extracted. The absorption coefficients of the extracts were measured as a function of ammonium ion aging time using UV-visible absorption spectrometry. The conclusions from all above chapters are summarized in Chapter 6.

Anthropogenic volatile organic compounds (VOCs) and semi-volatile organic (SVOCs) compounds are atmospheric pollutants contributing to the photochemical formation of tropospheric ozone. We combined adsorption and UV photolysis techniques for the removal and degradation of selected VOCs and SVOCs. For adsorption, we synthesized magnetite nanoparticles, a naturally occurring material, to avoid unknown detrimental impacts associated with new materials, as was the case with chlorofluorcarbons. The removal efficiency with magnetite was up to 98 % for aromatics, and 30% for light alkanes. Magnetite nanoparticles were regenerated, characterized (TEM, XRD, BET), and reused with no decrease in reported removal efficiencies. Photolysis alone removed up to 30% of aromatics, and less than 20% of light alkanes. The combination of adsorption, and photolysis did not improve the removal efficiency. Adsorption was attributed to London dispersion interactions for light alkanes, and to acid-base properties for aromatics. Reductions by photolysis were attributed to reactive radicals.
Les composés volatiles et semi-volatiles organiques de sources anthropogéniques sont des polluants atmosphériques participant à la formation d'ozone troposphérique. Nous avons associé l'adsorption et la photolyse par rayons ultraviolets, pour enlever et détruire ces composés. Nous avons synthétisé des nanoparticules de magnétite, un matériel abondant dans la nature, afin d'éviter la création d'un autre problème de pollution comme il est parvenu avec l'utilisation des fluorocarbure chlorés. L'efficacité d'enlèvement par adsorption atteint un maximum de 98 % pour les composés aromatiques et un maximum de 30% pour les alcanes légers. Les particules ont été regénérées, caractérisées (MET, XRD, BET), et réutilisées; aucune baisse en efficacité d'enlèvement n'est notée. Les expériences de photolyse atteignent une réduction maximale de 30% pour les composés aromatiques et de 20% pour les alcanes légers. Sous nos conditions expérimentales, aucune amélioration n'est notée par l'association des deux processus (adsorption et photolyse). La réduction par adsorption est attribuée aux forces d'attraction London pour les alcanes et aux propriétés acides et basiques pour les aromatiques. La réduction par photolyse s'explique par la formation de radicaux réactifs.

This project was the very beginning of research into the chemistry of eastern Australian banksia flowers. Using dynamic headspace sampling (DHS) analysis, differences in volatile components, consistent with detection of differences in odour, were detected among three different species and one commercial cultivar. Infraspecific variation was also observed between two known subspecies of Banksia ericifolia and between differently coloured forms of Banksia spinulosa var. collina. The cultivar, Banksia 'Giant Candles', was shown to have some of the chemical components of each of its supposed ancestors. The absence of known wound-response chemicals indicated that this DHS method was successful in leaving the inflorescences undamaged throughout the sampling procedure. The Likens-Nickerson modification of classical hydrodistillation methods was useful. The static headspace method (SHS) was easily automated and was shown to be chemically robust and sufficiently sensitive to detect volatile compounds from only a few flowers. The milder DHS method, which minimised mechanical and heat damage to the plant tissue, produced a different set of results. From the results of this project, a suite of volatile compounds has been proposed that may be useful in future behavioural studies to help determine whether animals are attracted to components of banksia odours. These candidates include some compounds that have been reported in animal secretions, wound-response chemicals that may be produced by the plant to aid its communication with other organisms, and a compound (suggested to be sulfanylmethyl acetate) not previously reported from natural sources. The mildest of the three analytical methods used, dynamic headspace sampling, was shown to be suitable for the potential chemotaxonomic evaluation of some members of the Banksia genus.
Doctor of Philosophy (PhD)

Thesis (Ph.D.) -- University of Western Sydney, Hawkesbury, 2001.
A thesis submitted as a requirement for the degree of Doctor of Philosophy, Centre for Biostructural and Biomolecular Research, University of Western Sydney, Hawkesbury, March 2001. Bibliography : leaves 177-185.

Exhaled breath is a rich and complex matrix containing many hundreds of compounds. Every breath offers the potential of a non-invasive measurement of the biochemical processes occurring in the human body and it is this notion that has led to the application of breath analysis for the detection of disease. With the majority of research in the field being focused on the detection of biomarkers, little has been presented on how the seemingly homeostatic matrix of breath varies during the course of normal life events. The research in this thesis describes how a subject's emotional state, physical state, and daily activities can alter the composition of exhaled breath.

In recent years, consumers have become increasingly interested in the quality aspects of food. Food quality, in turn, is strongly related to the sensory characteristics such as the flavor. Several scientific studies have shown that the Volatile Organic Compounds (VOCs) released by the food are related to the flavor and can be considered as assistive markers in the production chain. Today, the analysis of VOCs requires fast, non-invasive, and solvent free devices. It has been shown that the VOCs can be extracted, identified, and measured with a Gas Chromatography-Mass Spectrometry (GC-MS) without any pre-concentration or pre-treatment of the food. The main objective of this PhD thesis was to investigate the presence of volatile compounds in dairy products. More precisely, this study aimed in i) qualifying and quantifying VOCs in dairy products, ii) examining their formation and iii) integrating knowledge on VOCs by tracking their release during the whole production process from the raw materials till the final dairy product. In addition, statistical analysis was applied to link VOCs with the genetic characterization of animals, dairy system and individual cow-factors (e.g. stage of lactation, order of parity and milk yield). The identification and quantification of VOCs were performed using fast and non-invasive analytical approaches (Solid Phase Micro Extraction/Gas Chromatography-Mass Spectrometry SPME/GC-MS and Proton Transfer Reaction-Time of Flight-Mass Spectrometry PTR-ToF-MS) that can monitor the evolution of VOCs. To achieve the overall goal, the research was partitioned in four interrelated subparts as described below. The aim of the first chapter was to study the VOCs presence in the headspace of cheese. To this purpose, 150 cheeses ripened for two months were used. The cheeses were obtained through an individual model cheese-making approach using milk from individual Brown Swiss cows. Animals reared in 30 herds belonging to different dairy systems, from traditional (typical of the mountainous area) to modern ones. The study identified 55 VOCs classified in the chemical families of free fatty acids, esters, alcohols, aldehydes, ketones, lactones, terpenes, and pyrazines. We found that dairy system and individual cow characteristics (lactation stage, order of parity and daily milk yield) influenced the volatile compounds. In order, to test the instrument reproducibility and the model cheese-making procedure; data of GC analysis, order of injection of the sample into instrument, and vat were included in the statistical model. In many cases, these analytical factors did not affect the amount of VOCs released by cheese. In the second chapter, the potential of a new spectrometric technique (PTR-ToF-MS) was investigated to study cheese quality traits on a large scale. The PTR-ToF-MS allows direct injection of the sample headspace without extraction or pre-concentration steps, has a shorter analysis time (only a few seconds per sample) and greater sensitivity that permit to monitor on-line the evolution of volatile compounds. The resulting spectral information can provide a very detailed description of samples, which is useful for characterizing food quality and typicality. In particular, we analyzed the volatile fingerprint of 1,075 model cheeses produced using individual milk of Brown Swiss cows reared in 72 herds of different dairy systems. The output of PTR (spectrum) was characterized by more than 600 spectrometric peaks (variables). After removing interfering ions and background noise a set of 240 peaks was selected. Further, based on the results of the first contribution and literature, 61 peaks were identified. These peaks represent the major part of the cheese flavor. To summarize the amount of information, a multivariate analysis (PCA) was applied associating principal components (PC) with the 240 spectrometric peaks. Following, we tried to characterize the PCs through the correlations between PCs and the spectrometric peaks. The effects of dairy system, herd within dairy system, individual cows characteristics (lactation stage, order of parity and milk yield), and vat used for the cheese-making on the PCs and on the 240 peaks were analyzed. Dairy system was correlated with PC and 57 spectrometric peaks, especially when the herds were using Total Mixer Ration (TMR) as feeding technique, including or not maize silage in the diets. Regarding the individual animal characteristics, the most significant effect was the stage of lactation (139 peaks), followed by milk yield and parity, with 31 and 21 peaks, respectively. Finally, the vat used for the cheese-making was not found to be significant, confirming the good reproducibility of the model cheese-making procedure used to study cheese quality aspects. In the third chapter, the effect of cows’ genetics to the VOCs of ripened cheeses was assessed. Principal components and the 240 spectrometric peaks (as described above in the second contribution) were used fitting an animal model in a Bayesian framework. On average, heritability (h2) of 7% for PCs was found, which is similar to h2 of somatic cell count and much lower than the h2 of milk fat content and daily milk yield. It is interesting to note that only a small proportion of peaks showed very low h2 (<7%). The major part of them showed values similar to those found for PCs, while forty peaks presented heritability similar to that of milk yield and other milk quality traits. The variability attributed to the herd was different for the various PC. Results suggest a potential of improvement for several cheese VOCs through genetic selection in dairy cow breeding programs. The aim of the fourth chapter was to study the effect of summer transhumance on the quality traits of dairy products. Due to the extended work, this contribution was further splitted into two parts. In the first part, the evolution of milk and cheese quality characteristics were studied, while in the second part the evolution of VOC content of dairy products was analyzed. For the first part, chemical characteristics and technological properties of 11 dairy products obtained during summer transhumance of cows to Alpine pastures (Malga) were analyzed. Dairy products obtained throughout this period are known to give origin to high-value, healthier products, and extra tasty,. Bulk milk from 148 dairy cows reared day and night on Alpine pasture (1,860 m a.s.l.) was used. We performed 7 experimental cheese-making according to traditional mountain techniques, one every two weeks, using milk produced during the summer transhumance (from June to September). For each cheese-making we collected: milk from the evening milking (day before the cheese-making), the same milk the following morning (after natural creaming), the cream separated, the whole milk from the morning milking, the milk in vat obtained mixing the creamed evening milk with the whole morning milk, the fresh curd, the whey, the ricotta obtained from whey, and the residual scotta. Moreover, the curd was used to produce typical “Malga” cheese that was ripened for 6 and 12 months. The chemical characteristics were measured with infrared technology. Results highlighted variation in milk yield, milk chemical composition, cheese yield and curd recoveries and/or loss of nutrients in the traditional cheese-making. In particular, a reduction of milk yield, fat, protein and lactose contents of milk during summer transhumance was observed. Nevertheless, the return to lowland farming systems of the cows at the end of grazing season, positively affected milk yield and milk chemical composition. The average of cheese yield was 14.2%, while recoveries of fat, protein, total solids and energy were 85.1%, 77.8%, 49.4% and 58.1%, respectively. These results were in accordance to those found in the literature. For the second part of this chapter, the VOCs content of sample headspace was measured through SPME/GC-MS. Forth nine VOCs belonging to the chemical families of alcohols, aldehydes, free fatty acids, ketones, esters, lactones, terpenes, phenolic, and sulphur compounds were detected. In addition, the evolution of VOCs and their chemical family across the cheese- and ricotta-making processing as well as during the cheese ripening period was tracked. The comparison between VOCs concentration of 4 types of milk (whole evening, creaming milk, whole morning, milk in vat) showed that the creaming process significantly affected about half of all the volatile organic compounds analyzed, followed by the effects of milking (evening milking vs. morning milking) and the mixing (creamed milk mixed with whole morning milk). In general, the cream, in contrast to curd and ricotta, showed higher content of free fatty acids, sulphurs and terpenes compounds. Moreover, in ricotta a higher VOC concentration was observed compared to the curd, probably due to the high temperature required during the ricotta process. The effect of the progressive nutrient depletion of milk was investigated by contrasts between VOC concentration of milk in the vat, whey, and scotta. Although milk contains a greater amount of nutrients, whey and scotta have shown a higher concentration of VOCs with the exceptions of esters, sulphurs, terpenes and phenolic compounds. Finally, the effect of ripening was tested by comparing the quantity of VOCs of curd and of aged cheeses (6 and 12 months). The release of volatile compounds increased with increasing ripening period in relation with the enzymatic and microbiological activity of cheese. In summary, the spectrometric techniques (SPME/GC-MS and PTR-ToF-MS) used in this work demonstrated to be very efficient to characterize the volatile organic compounds of dairy products. The dairy system, and cow related factors affected the volatile fingerprint of ripened cheeses. Particularly, concerning the individual animal source of variation, lactation stage was the most important effect followed by the cow’s parity and the milk yield. On the basis of phenotypes used in this work, the traits collected offered the potential for a genetic analysis to be carried out. The genetic analysis demonstrated the existence of an exploitable genetic variability of the volatile profile of cheese that might be useful for an (in)direct selection of dairy cows for cheese quality traits in breeding programs. Nevertheless, further research is needed in this area. In the era of genomics for e.g., it might be interesting to associate genomic regions to specific VOCs. This information might be useful for genomic breeding programs. The evolution of volatile compounds across the production chain depends on specific technological aspects, such as the process of natural creaming, the temperature of coagulation, and the ripening period. The monitoring of volatile fingerprint permits to obtain dairy products with specific organoleptic characteristics useful to differentiate them on the market and to improve the supply chain efficiency on the basis of quality aspects.
Negli ultimi anni, il consumatore è diventato sempre più sensibile agli aspetti qualitativi degli alimenti, i quali sono fortemente influenzati dalle caratteristiche sensoriali come l’aroma. Diversi lavori scientifici hanno dimostrato che i composti volatili (VOCs) rilasciati dall’alimento sono correlati con il suo aroma e possono essere considerati come traccianti delle filiere alimentari. Oggi, l’analisi dei VOCs richiede strumenti rapidi, sensibili, non invasivi e che abbiano bisogno dell’impiego di pochi solventi durante la preparazione del campione. E’ stato dimostrato che i VOCs possono essere estratti, misurati e identificati con la Gas Cromatografia di Massa (GC-MS) senza pre-concentrazioni o pre-trattamenti dell’alimento da analizzare. Gli obiettivi principali della tesi di dottorato erano di studiare la presenza di composti volatili nei prodotti lattiero-caseari. Più precisamente, questo studio aveva come obiettivi di i) qualificare e quantificare i VOCs nei prodotti lattiero-caseari, ii) esaminare la loro formazione e iii) integrare le conoscenze acquisite su questi composti attraverso tutta la filiera di produzione dalla materia prima fino al prodotto finito. Inoltre, analisi statistiche sono state utilizzate per collegare i VOCs con la caratterizzazione genetica degli animali, il sistema di allevamento e le caratteristiche individuali delle vacche (es. stadio di lattazione, ordine di parto e produzione giornaliera di latte). L’identificazione e la quantificazione dei VOCs sono state fatte utilizzando tecniche analitiche precise, veloci e non invasive (Solid Phase Micro Extraction/Gas Chromatography-Mass Spectrometry SPME/GC-MS and Proton Transfer Reaction-Time of Flight-Mass Spectrometry PTR-ToF-MS). Per rispondere agli obiettivi generali della tesi, l’attività di ricerca è stata divisa in cinque parti connesse tra di loro. L’obiettivo nel primo capitolo era di studiare i composti volatili presenti nello spazio di testa di campioni di formaggio. Per questo scopo, sono stati analizzati 150 formaggi stagionati per due mesi. I formaggi sono stati prodotti utilizzando una metodica di caseificazione individuale usando latte individuale di vacche di razza Bruna. Gli animali sono stati allevati in 30 aziende appartenenti a diversi sistemi di allevamento, da tradizionale (tipico della realtà montana) a moderno. In questo studio sono stati identificati 55 VOCs per ogni formaggio, classificati in diverse famiglie chimiche: acidi grassi, esteri, alcoli, aldeidi, chetoni, lattoni, terpeni e pirazine. Dai risultati emerge che il sistema di allevamento e le caratteristiche individuali delle vacche (stadio di lattazione, ordine di parto e produzione giornaliera di latte) influenzano i composti volatili. Inoltre, per testare la riproducibilità dello strumento e della metodica di caseificazione; la data di analisi cromatografica, l’ordine d’iniezione del campione nello strumento (GC), e la caldaia di caseificazione erano inclusi nel modello statistico. In molti casi, questi fattori analitici/strumentali non influenzano la quantità di VOCs rilasciata dai formaggi. Nel secondo capitolo, il potenziale di una nuova tecnica analitica (PTR-ToF-MS) è stato approfondito per studiare, su larga scala, le caratteristiche qualitative del formaggio. Il PTR-ToF-MS dal punto di vista analitico, permette un’iniezione diretta del campione senza estrazione o pre-concentrazione, ha un breve tempo di analisi (solo pochi secondi per campione) e grande sensibilità consentendo di monitorare in tempo reale l’evoluzione dei composti volatili. L’analisi produce uno spettro molto dettagliato che può essere utile per la caratterizzazione delle qualità e della tipicità dell’alimento. In particolare, è stata analizzata l’impronta aromatica di 1,075 formaggi prodotti utilizzando latte individuale di vacche di razza Bruna allevate in 72 aziende appartenenti a diversi sistemi di allevamento. L’impronta aromatica (spettro) era caratterizzata da più di 600 picchi (variabili) per ogni formaggio. Gli spettri sono stati analizzati e dopo la rimozione degli ioni interferenti e del rumore di fondo è stato selezionato un data set costituito da 240 picchi per ogni formaggio. In seguito, basandosi sui risultati del primo contributo e sulla letteratura sono stati identificati i picchi più importanti (61) in termini quantitativi e qualitativi. Per sintetizzare la quantità di informazioni ovvero estrarre delle componenti principali (PC) è stata fatta un’analisi multivariata (PCA) a partire dai 240 picchi spettrometrici. In seguito, le PCs sono state caratterizzate sulla base delle loro correlazioni con i 240 picchi spettrometrici. Sono stati analizzati gli effetti del sistema di allevamento, dell’azienda entro sistema di allevamento, le caratteristiche individuali delle vacche (stadio di lattazione, ordine di parto e produzione di latte), e caldaia di caseificazione sulle PCs e sui 240 picchi. Dai risultati emerge che il sistema di allevamento è correlato con le PC e 57 picchi, specialmente quando le aziende come tecnica di alimentazione utilizzano il carro miscelatore (TMR) con e senza insilati nella dieta. Considerando le caratteristiche individuali delle vacche, l’effetto più significativo è lo stadio di lattazione (139 picchi), seguito dalla produzione di latte e dall’ordine di parto, con 31 e 21 picchi, rispettivamente. Infine, la caldaia di caseificazione è un effetto spesso non significativo, confermando la buona riproducibilità della micro-caseificazione utilizzata anche per lo studio di aspetti qualitativi del formaggio. Nel terzo capitolo è stato studiato l’effetto della genetica dell’animale sui composti volatili dei formaggi. A tale scopo, sono state analizzate le componenti principali (estratte come discusso sopra nel secondo contributo) e i 240 picchi spettrometrici (PTR-ToF-MS) utilizzando un modello animale con un approccio Baesiano. Dai risultati emerge in media un’ereditabilità (h2) del 7 % per le componenti principali, la quale è simile all’h2 trovata per le cellule somatiche e leggermente più bassa di quella del contenuto di grasso nel latte e della produzione giornaliera di latte stimate in precedenza sugli stessi animali. E’ interessante osservare che solo una piccola quantità di picchi ha una bassa h2 (<7%). La maggior parte di essi presenta valori simili a quelli trovati per le PCs, mentre 40 picchi presentano ereditabilità simile a quella trovata per la produzione giornaliera di latte e ad altre caratteristiche qualitative del latte. La variabilità attribuita all'azienda è risultata diversa per le PCs. Questi risultati dimostrano che esiste un’interessante variabilità genetica di alcuni VOCs che potrebbe essere potenzialmente utilizzata nei programmi di miglioramento genetico. L’obiettivo nel quarto capitolo era di studiare l’effetto della transumanza sulle caratteristiche qualitative di prodotti lattiero-caseari. Vista la grande mole di dati, questo contributo è stato diviso in due parti tra loro connesse. Nella prima parte è stata studiata l’evoluzione della qualità del latte e del formaggio, mentre nella seconda parte è stata analizzata l’evoluzione dei composti volatili dei prodotti lattiero-caseari nel processo di caseificazione. Nella prima parte, sono state analizzate le proprietà fisiche, chimiche e tecnologiche di 11 prodotti lattiero-caseari raccolti durante la transumanza al pascolo Alpino (Malga) di vacche da latte. E’ risaputo che i prodotti ottenuti durante il periodo di alpeggio possono avere un valore aggiunto dovuto alle elevate proprietà nutrizionali, salutistiche e aromatiche. Per approfondire le conoscenze finora acquisite, è stata fatta questa prova in cui è stato utilizzato il latte di massa prodotto da 148 vacche allevate giorno e notte al pascolo (1,860 m s.l.m.). Durante l’esperimento, sono state fatte 7 caseificazioni seguendo tecniche tradizionali, una ogni 2 settimane, utilizzando il latte prodotto durante la transumanza (da giugno a settembre). Sono stati raccolti per ogni caseificazione: il latte della mungitura della sera (giorno prima della caseificazione), lo stesso latte il mattino successivo (dopo il processo di scrematura naturale), la panna di affioramento, il latte della mungitura del mattino, il latte in caldaia ottenuta dalla miscela tra il latte scremato della mungitura della sera con il latte della mungitura del mattino, la cagliata, il siero, la ricotta ottenuta dal siero e il residuo della lavorazione ossia la scotta. Inoltre, la cagliata è stata usata per produrre formaggi di “Malga” che sono stati stagionati per 6 e 12 mesi. Le caratteristiche chimico-fisiche sono state misurate con una tecnologia a infrarosso. I risultati dimostrano una variazione della produzione giornaliera e composizione chimica del latte, resa in formaggio e recupero/o perdita di nutrienti nel processo di caseificazione tradizionale. In particolare, si è osservata una riduzione della produzione giornaliera di latte, grasso, proteine e lattosio del latte durante la transumanza estiva. Tuttavia, si è anche osservato un effetto positivo sulla produzione e la composizione chimica del latte del ritorno delle vacche nelle aziende di fondo valle alla fine della stagione dell’alpeggio. La resa media di formaggio in questo lavoro è risultata del 14.2%, mentre i recuperi di grasso, proteine, solidi totali ed energia sono del 85.1%, 77.8%, 49.4% e 58.1%, rispettivamente. Questi risultati sono in linea con quelli trovato in letteratura. Nella seconda parte di questo contributo, è stato misurato il contenuto di composti volatili nello spazio di testa dei campioni con la tecnica SPME/GC-MS. Dopo l’analisi, sono stati identificati 49 VOCs appartenenti alle famiglie chimiche degli alcoli, aldeidi, acidi grassi, chetoni, esteri, lattoni, terpeni e composti solforati e fenolici. Inoltre, è stata studiata l’evoluzione dei VOCs e delle loro famiglie chimiche attraverso i processi di caseificazione, di produzione della ricotta e di stagionatura del formaggio. Il confronto tra la concentrazione dei VOCs dei 4 tipi di latte (intero e scremato della sera, intero del mattino, caldaia) ha dimostrato che il processo di scrematura influenza la concentrazione di metà dei composti volatili analizzati, seguito dall’effetto della mungitura (intero della sera vs. intero del mattino) e dall’effetto del mescolamento (latte scremato della sera mescolato in parti uguali con il latte del mattino). In generale, la panna, rispetto a cagliata e ricotta, ha un maggiore contenuto di acidi grassi, terpeni e composti solforati. Inoltre, la ricotta rispetto alla cagliata ha un’elevata concentrazione di VOC, probabilmente dovuta alla maggiore temperatura utilizzata durante il processo di produzione. L’effetto del progressivo depauperamento di nutriente del latte è stato studiato attraverso il confronto tra latte in caldaia, siero e scotta. Sebbene il latte abbia un maggiore contenuto di nutrienti, il siero e la scotta hanno una maggiore concentrazione di VOC ad eccezione delle famiglie chimiche degli esteri, terpeni, composti solforati e fenolici. Infine, l’effetto della maturazione è stato valutato attraverso il confronto tra le quantità di VOC della cagliata e dei formaggi stagionati (6 e 12 mesi). Il rilascio dei composti volatili incrementa con l’aumento del periodo di maturazione probabilmente dovuto a una maggiore attività enzimatica e microbiologica nel formaggio. In conclusione, le tecniche analitiche di spettrometria di massa utilizzate in questo lavoro (SPME/GC-MS e PTR-ToF-MS) hanno permesso di caratterizzare i composti volatili dei prodotti lattiero-caseari in maniera efficiente. Il sistema di allevamento, le caratteristiche individuali delle vacche hanno influenzato l’impronta aromatica di formaggi individuali stagionati. In particolare, riguardo alle caratteristiche individuali degli animali il principale effetto era lo stadio di lattazione seguito da ordine di parto e produzione giornaliera di latte. Sulla base dei fenotipi raccolti in questo lavoro è stato possibile effettuare un’analisi genetica, la quale ha dimostrato l’esistenza di un’interessante variabilità genetica connessa ai composti volatili del formaggio che potrebbe essere utile per una selezione (in)diretta delle vacche da latte sulla base di aspetti qualitativi in programmi di miglioramento genetico. Tuttavia sono necessarie altre ricerche in quest’area per esempio, nell’era della genomica, sarebbe interessante associare qualche regione specifica del genoma ai composti volatili. L’evoluzione dei composti volatile attraverso la filiera di produzione dipende da specifici aspetti tecnologici, come l’affioramento della panna, la temperatura di coagulazione e il periodo di stagionatura. Il monitoraggio dell’impronta aromatica permette di ottenere prodotti lattiero-caseari con delle specifiche caratteristiche organolettiche utili a differenziare il prodotto sul mercato e a migliorare l’efficienza dell’intera filiera produttiva sulla base di aspetti qualitativi.

Volatile organic compounds (VOCs) are the key aroma producers in fruits and sensory quality of fruits is widely determined by qualitative and quantitative composition of VOCs. The aroma of grape is a complex of hundreds of VOCs belonging to different chemical classes like alcohols, esters, acids, terpenes, aldehydes, furanones, pyrazines, isoprenoids and many more. VOCs play important role as they determine the flavor of grapes and wine made from it. The objective of this thesis is to study of VOCs through development of different mass spectrometry based analytical methodologies and its applications for the comprehensive investigation and construction of database of the VOCs in grapes. First part of the study was dedicated to generation of the comprehensive database of grape VOCs through the screening of multiple grape varieties (n=124) representing different species, color and origin. The experiment was carried out using headspace solid-phase microextraction (HS-SPME) and gas chromatography mass spectrometry (GC-MS) based approach and according to metabolomics protocols. A customized dataset of reference standards (>350) was generated and, an automated pipeline for data analysis was created in collaboration with data management group of the institute. The results showed annotation of “level 1†of 117 VOCs in grape. The established database in this experiment will represent the significant portion of the future Grape Metabolome database. The second part of the study was dedicated to study the differential behavior of volatile organic compounds and their glycosylated precursors qualitatively and semi quantitatively. Volatile secondary metabolites also exist in the form of nonvolatile and odorless glycosylated precursors in grape and studies have confirmed that concentration of these precursors can be much higher than its free counterparts. The elevated concentrations of volatiles in glycosylated forms can significantly affect the wine aroma because of possible chemical modifications throughout the process of fermentation and wine ageing. In addition, the investigation of the biosynthesis and accumulation of VOCs in the fruit tissues requires the consideration of both the free and bound forms. To study the phenomenon an experiment was carried using solid phase extraction (SPE) of the free and glycosylated precursors; with enzymatic hydrolysis aglycone part of the precursors was released followed by subsequent GC-MS analysis. Over 10 different selected grape varieties were analyzed. Sixty-six significant different aroma compounds in grapes (pre and post hydrolysis) were identified. Identification was done based on several parameters like retention time, retention index and MS spectral database. The multivariate statistical analysis by two-way hierarchical clustering with heat map visualization showed distribution of the compounds within different varieties before and after hydrolysis. In the third part of the study, we performed experiments dedicated to training and applications of atmospheric pressure gas chromatography mass spectrometry (APGC-MS). The experiment was carried out at the Department of Biological Sciences, University of North Texas, under the supervision of Prof. Vladimir Shulaev. We have established the metabolomics protocol for the analysis of fruit volatiles using APGC-MS with an optimized GC and MS conditions and created novel library of the fruit volatile compounds using APGC-MS system. Six different grape varieties were analyzed as a case study and experimental results showed APGC-MS as a valuable solution for metabolomics analysis. The data processing and statistical evaluation was done using XCMS and progenesis QI© software. Moreover, observations based on injections of pure reference standards showed high abundance of molecular ions with minimal fragmentation at low collision energy that is typically missing in traditional vacuum source GC-MS. Moreover, the use of elevated collision energy data resulted in a spectrum similar to the traditional EI data.

Volatile organic compounds (VOCs) are the key aroma producers in fruits and sensory quality of fruits is widely determined by qualitative and quantitative composition of VOCs. The aroma of grape is a complex of hundreds of VOCs belonging to different chemical classes like alcohols, esters, acids, terpenes, aldehydes, furanones, pyrazines, isoprenoids and many more. VOCs play important role as they determine the flavor of grapes and wine made from it. The objective of this thesis is to study of VOCs through development of different mass spectrometry based analytical methodologies and its applications for the comprehensive investigation and construction of database of the VOCs in grapes. First part of the study was dedicated to generation of a database of grape VOCs through the screening of multiple grape varieties (n=124) representing different species, color and origin. The experiment was carried out using headspace solid-phase microextraction (HS-SPME) and gas chromatography mass spectrometry (GC-MS) based approach and according to metabolomics protocols. A customized dataset of reference standards (>350) was generated and, an automated pipeline for data analysis was created in collaboration with data management group of the institute. The results showed annotation of “level 1”of 117 VOCs in grape. The established database in this experiment will represent the significant portion of the future Grape Metabolome database. The second part of the study was dedicated to study the differential behavior of volatile organic compounds and their glycosylated precursors qualitatively and semi quantitatively. Volatile secondary metabolites also exist in the form of nonvolatile and odorless glycosylated precursors in grape and studies have confirmed that concentration of these precursors can be much higher than its free counterparts. The elevated concentrations of volatiles in glycosylated forms can significantly affect the wine aroma because of possible chemical modifications throughout the process of fermentation and wine ageing. In addition, the investigation of the biosynthesis and accumulation of VOCs in the fruit tissues requires the consideration of both the free and bound forms. To study the phenomenon an experiment was carried using solid phase extraction (SPE) of the free and glycosylated precursors; with enzymatic hydrolysis aglycone part of the precursors was released followed by subsequent GC-MS analysis. Over 10 different selected grape varieties were analyzed. Sixty-six significant different aroma compounds in grapes (pre and post hydrolysis) were identified. Identification was done based on several parameters like retention time, retention index and MS spectral database. The multivariate statistical analysis by two-way hierarchical clustering with heat map visualization showed distribution of the compounds within different varieties before and after hydrolysis. In the third part of the study, we performed experiments dedicated to training and applications of atmospheric pressure gas chromatography mass spectrometry (APGC-MS). The experiment was carried out at the Department of Biological Sciences, University of North Texas, under the supervision of Prof. Vladimir Shulaev. We have established the metabolomics protocol for the analysis of fruit volatiles using APGC-MS with an optimized GC and MS conditions and created novel library of the fruit volatile compounds using APGC-MS system. Six different grape varieties were analyzed as a case study and experimental results showed APGC-MS as a valuable solution for metabolomics analysis. The data processing and statistical evaluation was done using XCMS and Progenesis QI© software. Moreover, observations based on injections of pure reference standards showed high abundance of molecular ions with minimal fragmentation at low collision energy that is typically missing in traditional vacuum source GC-MS. Moreover, the use of elevated collision energy data resulted in a spectrum similar to the traditional EI data.

Volatile organic compounds (VOCs) are the key aroma producers in fruits and sensory quality of fruits is widely determined by qualitative and quantitative composition of VOCs. The aroma of grape is a complex of hundreds of VOCs belonging to different chemical classes like alcohols, esters, acids, terpenes, aldehydes, furanones, pyrazines, isoprenoids and many more. VOCs play important role as they determine the flavor of grapes and wine made from it. The objective of this thesis is to study of VOCs through development of different mass spectrometry based analytical methodologies and its applications for the comprehensive investigation and construction of database of the VOCs in grapes. First part of the study was dedicated to generation of the comprehensive database of grape VOCs through the screening of multiple grape varieties (n=124) representing different species, color and origin. The experiment was carried out using headspace solid-phase microextraction (HS-SPME) and gas chromatography mass spectrometry (GC-MS) based approach and according to metabolomics protocols. A customized dataset of reference standards (>350) was generated and, an automated pipeline for data analysis was created in collaboration with data management group of the institute. The results showed annotation of “level 1”of 117 VOCs in grape. The established database in this experiment will represent the significant portion of the future Grape Metabolome database. The second part of the study was dedicated to study the differential behavior of volatile organic compounds and their glycosylated precursors qualitatively and semi quantitatively. Volatile secondary metabolites also exist in the form of nonvolatile and odorless glycosylated precursors in grape and studies have confirmed that concentration of these precursors can be much higher than its free counterparts. The elevated concentrations of volatiles in glycosylated forms can significantly affect the wine aroma because of possible chemical modifications throughout the process of fermentation and wine ageing. In addition, the investigation of the biosynthesis and accumulation of VOCs in the fruit tissues requires the consideration of both the free and bound forms. To study the phenomenon an experiment was carried using solid phase extraction (SPE) of the free and glycosylated precursors; with enzymatic hydrolysis aglycone part of the precursors was released followed by subsequent GC-MS analysis. Over 10 different selected grape varieties were analyzed. Sixty-six significant different aroma compounds in grapes (pre and post hydrolysis) were identified. Identification was done based on several parameters like retention time, retention index and MS spectral database. The multivariate statistical analysis by two-way hierarchical clustering with heat map visualization showed distribution of the compounds within different varieties before and after hydrolysis. In the third part of the study, we performed experiments dedicated to training and applications of atmospheric pressure gas chromatography mass spectrometry (APGC-MS). The experiment was carried out at the Department of Biological Sciences, University of North Texas, under the supervision of Prof. Vladimir Shulaev. We have established the metabolomics protocol for the analysis of fruit volatiles using APGC-MS with an optimized GC and MS conditions and created novel library of the fruit volatile compounds using APGC-MS system. Six different grape varieties were analyzed as a case study and experimental results showed APGC-MS as a valuable solution for metabolomics analysis. The data processing and statistical evaluation was done using XCMS and progenesis QI© software. Moreover, observations based on injections of pure reference standards showed high abundance of molecular ions with minimal fragmentation at low collision energy that is typically missing in traditional vacuum source GC-MS. Moreover, the use of elevated collision energy data resulted in a spectrum similar to the traditional EI data.

Volatile and semi-volatile organic compounds are ubiquitous, and some of them are hazardous. The ability to rapidly detect and identify trace levels of them in air has become increasingly important. The conventional device used today for sampling and concentrating them in air is thermal desorption tubes filled with specific sorbents, which can only collect air samples at flow rates of 100-200 mL/min. In order to detect low concentration (ppt level) VOC compounds, long sampling time (>2 h) and sensitive detection are required. At the same time, portable instrumentation for on-site analysis has been developing rapidly. The somewhat lower performance of portable instruments compared to benchtop systems requires the sampling of even greater sample volume in order to reach the same detection limits. In this study, two high flow rate air sampling devices, i.e., a multi-capillary trap and a concentric packed trap, were developed to sample a large volume of air in a short time period. The multi-capillary trap was constructed by bundling analytical capillary gas chromatography columns together in parallel. As low as single digit ppt detection limits were reached in less than 25 min with this trap, and as high as 8.0 L/min flow rate was sampled. The simple and compact multi-capillary trap could be easily used with a conventional thermal desorption system to perform high flow rate sampling. A concentric packed high flow rate trap was also developed by packing sorbent layers concentrically around an empty tube. The concentric packed trap achieved a high flow rate (>10 L/min) because it had a high surface area and short sorbent bed. Also, its large sorbent amount (>1 g) provided large breakthrough volume (>100 L) required to achieve low detection limits. An equilibrium distribution sampling system was developed by absorbing selected analytes in granular PDMS to provide calibration for on-site instrumentation. Furthermore, a needle trap device was coupled in tandem to both high flow rate air samplers to perform second-stage concentration of VOCs down to the ppt level. Concentration factors of 104 to 105 were achieved within 30 min using both systems, i.e., over 10 to 100 times more sample was collected compared to conventional TD systems.

Methylzinc tetrahydroborate, [MeZnBH₄], has been prepared by two routes and the structure of the solid determined by X-ray crystallography to reveal helical polymers in which MeZn and BH₄ units alternate. The latter functions as a bidentate ligand with respect to each of the adjacent metal atoms. Investigation by mass spectrometry and matrix isolation shows that the vapour consists of an equilibrium mixture of monomeric and dimeric species. The pattern of infrared bands for the monomer is characteristic of a bidentate BH₄ group, a finding consistent with the results of DFT calculations. Disproportionation into [Me₂Zn] and [Zn(BH₄)₂] is a common feature of the chemistry of methylzinc tetrahydroborate, although it has been possible to isolate and characterize the adduct [MeZnBH₄.SMe₂]. The reaction between [B₄H₁₀ and [Me₂Zn] in the gas phase affords colourless acicular crystals of [(MeZn)₂B₃H₇] in yields of ca. 10%. This compound has been characterized by chemical analysis and by NMR and vibrational spectroscopy. X-ray crystallography reveals that the product is a dimer, [(MeZn)₂B₃H₇]₂, featuring two distinct zinc environments. Two B₃H₇ZnNe ligands, formally derived from B₃H₈ by replacement of a µ₂-H by a µ₂-ZnMe unit, each function in a bis(bidentate) manner linking together two other MeZn centres through pairs of Zn-H-B bridges. The structures of several aluminium tetrahydroborates in the solid phase have been investigated by X-ray diffraction. The structure of dimethylaluminum tetrahydroborate has been shown to consist of helical polymeric chains in which Me₂-Al and BH₄ units alternate. Here, too, the BH₄ groups exhibit bidentate ligation with respect to each of the adjacent metal atoms, although the degree of interaction between the metal centre and the BH₄ group is somewhat less than in [MeZnBH₄ ]. Solid aluminium tris(tetrahydroborate) exhibits two phases with a transition temperature in the range 180-195 K. Each phase is made up of discrete Al(BH ₄ )₃ units, the principal differences relating to the packing of the individual molecules. In the a phase the Al(BH ₄ )₃ molecules display an angle of 78.2° between the AlB₃ and Al(µ-H)₂ planes and are disposed about a 2₁ crystallographic screw axis; in the ß phase the molecular units conform to D_3h symmetry. Dimethylindium octahydrotriborate, [Me₂ lnB₃ H₈ ], has been synthesized by the reaction between trimethylindium and tetraborane(10) and characterized by chemical analysis and by NMR and vibrational spectroscopy. X-ray diffraction of a single crystal reveals that the solid consists of [Me₂ lnB₃ H₈] units, although there is evidence of charge separation in the sense [Me₂ln]⁺[B₃ H₈ ]^- and of secondary interaction between terminal hydrogen atoms and adjacent indium centres. The infrared spectrum of the matrix-isolated vapour is consistent with a monomeric structure similar to that of [Me₂ AlB₃ H₈].

Odorous volatile organic compounds emissions from fried-food industries posed severed pollution problems both to the workers and the surrounding inhabitants. These industries need to look for cost effective and efficient methods to reduce these emitted gases.  Several solutions such as the use of centrifugation, scrubbers, ion exchangers, biofiltration, condensation, adsorption, absorption, and incineration have been exploited to reduce these smelling gases. Centriair in collaboration with KTH aim at using UV light in combination with ozone and hydrogen peroxide to degrade these odorous VOCs emitted from the frying of meat balls (SCAN) and chips. Several volatile organic compounds which are odorants with low threshold values were identified in the emitted gases from meat frying which includes: aldehydes, sulphur containing compounds, ketones, pyrazines, and alcohols. The type and concentration of these odorants emitted depends among other things primarily on the type of oil used during the frying process.  This work focuses on the use of advanced oxidation processes to abate theses odorous gases. The effect of UV dosage and the use of hydrogen peroxide were tested in a flow reactor. Ozone producing UV lamps were used for the treatment of 2,4-decadienal, Hexanal, furfural, and 2,5-dimethylpyrazine. A simultaneous chemical and odour analysis was done using a GC/MS Olfactometry system. UV/Ozone/H2O2 was effective in reducing the volatile organic compounds tested thus reducing the odor concentration. The percent removal was proportional to the energy dosage.

The research focuses on the environmental problem of volatile organic compounds in ambient air of petrol filling stations. The literature review of the issues, arising from petrol-related VOCs, with actual and proposed VOC emissions trends in Europe, have been performed. Besides petrol filling station’s typical technology layout, petrol nature and composition, applicable petrol vapour recovery solutions and their efficiency were examinated. The volatile organic compounds’ experimental research in two petrol stations of typical technology layout in Vilnius city under similar extreme meteorological conditions (VOC air pollution episodes with low winds, stable stratification and suspended photochemical removal) is done. The emitted from petrol stations VOC experiment is based on air pumped sampling in glass gas pipette and further determination using gas chromatography with flame ionization detector. The experimental results, presented by means of tables and diagrams, are analysed and discussed. The available results of the experiment are loaded into the environmental model “ALOHA” for air pollution evaluation and concentrations prediction in the ambient air under different meteorological conditions and technological emergency situations (petrol spillage) at petrol filling station. The research is summarized in conclusions and recommendations.
Tyrimas skirtas aplinkos oro taršos problemai lakiaisiais organiniais junginiais, išsiskiriančiais nuo benzino degalinių. Atlikta svarstomos aplinkosauginės problemos literatūros apžvalga. Apžvelgti oro taršos pasekmės skatinamos LOJ išsiskyrimų nuo benzino degalinių, aktualios ir numatomos LOJ emisijų tendencijos Europoje, tipinis benzino degalinės technologijos išsidėstymas, benzino sudėtis ir svarbiausios LOJ garų formavimui benzino savybės, taikomi garų grąžinimo sprendiniai ir jų efektyvumas. Detaliai aprašytas LOJ eksperimentinis tyrimas, atliktas dviejose Vilniaus miesto tipinės technologijos degalinėse esant panašioms kraštutinėms (LOJ taršos epizodai prie silpnų vėjų, stabilios stratifikacijos ir suspenduoto fotocheminio šalinimo) meteorologiniams sąlygoms. LOJ mėginių ėmimui panaudotas aktyvus metodas su aspiracija į dujines pipetes, LOJ koncentracijos nustatytos dujinės chromatografijos su liepsnos jonizacijos detektoriumi metodu. Tyrimo rezultatai, pateikti lentelių ir diagramų pavidalu, aptarti ir įvertinti. Eksperimento duomenys įkelti į oro kokybės modelį “ALOHA”, siekiant nustatyti LOJ pernašą ir sudaryti LOJ koncentracijų prognozė benzino degalinių aplinkos ore prie skirtingų meteorologinių parametrų ir avarinių technologinių situacijų (benzino išsiliejimas). Tiriamąjį darbą reziumuoja išvados ir rekomendacijos.

The preparation, testing and characterisation of catalysts for the total oxidation of two volatile organic compounds (VOCs) have been studied. These two VOCs were naphthalene and propane. Naphthalene was the main focus of this study. CeZrC>2 with varied Ce:Zr ratios and preparation methods was investigated for the total oxidation of naphthalene. These preparation methods were all precipitation methods using different precipitating agents (urea, sodium carbonate and supercritical CO₂). Zr contents as low as 1 molar percent enhanced activity for both urea and sodium carbonate precipitated catalysts compared to CeC>2. A supercritical analogue was found to be less active. Pt/SiC>2 as a catalyst for naphthalene total oxidation was studied with a view to optimise an existing impregnation technique. A Pt loading of 2.5wt% with a calcination regime of 550 °C for 12h in static air with a ramp rate of 5 °C/min was found to be optimal. These preparation conditions were found to increase the proportion of metallic Pt which was found to exist as large crystallites with low dispersion. Other catalyst features were probed in this study. The type of silica used as a support was changed to novel hollow sphere silica then nanopore silica but no improvement in activity was found. Pt was then substituted for Pd which again did not improve activity. It was found that the Pd existed as Pd oxide hence Pd oxide is not as active for naphthalene oxidation as metallic Pt. The preparation of impregnated catalysts using non-aqueous solvents on so-called 'hydrophobic' materials was also investigated. These were tested for both naphthalene and propane total oxidation. It was found that Pt and Pd based catalysts afforded the most active catalysts. Several supports were studied which interacted with the impregnated metals in different ways. This affected the nature of the impregnated metals and therefore the activities of these catalysts. Some of the more active catalysts used supports that were of a low surface area. A high surface area SnO₂ support was produced and impregnated with Pd. The high surface area SnO₂ was found to be more active than the original Pd/SnO₂ catalyst for propane total oxidation.

There is increasing concern regarding the indoor air quality of energy efficient buildings. Indoor air pollutants, such as volatile organic compounds (VOCs) and particulates, commonly found in buildings, can be harmful to human health. Interior materials are known to be one of the main contributors to poor indoor air quality. There is a need to develop natural materials and systems in order to minimise the level of indoor air pollutants, or even reduce them to near zero through the use of VOC-free emitters and exploitation of the sink effect for airborne pollutants. Natural building materials are considered to possess low embodied energy and are environmentally-friendly. The aim of this research was to investigate the physical and chemical interactions between natural building materials and VOCs in new or refurbished buildings (e.g. dwellings, offices, hospitals, schools and retail outlets). Key to this was the identification of low VOC emission materials with the added benefit of passively improving the indoor air quality. Comprehensive chemical and physical characterisation of materials was undertaken in order to understand the mechanisms involved in the capture of VOCs by three classes of natural building materials: insulation, coatings and wood panels. In order to understand the interactions between VOCs and building materials, adsorption and desorption experiments were carried out in laboratory-scale environmental chambers and in a real size room with a volume of 30 m3, all with controlled temperature, relative humidity and air flow-rate. Four organic pollutants commonly found in indoor environments were selected for this study according to their physico-chemical properties: formaldehyde, toluene, limonene and dodecane. In the first stage of this research, TVOC and formaldehyde emissions from 18 commercially available natural building materials were analysed (six insulation materials, six coatings and six wood-based panels). These materials included natural wool, hemp fibres, wood fibres, gypsum, lime mortars, clay-based plasters and wood-based plasters. Four of these materials were selected to investigate their adsorption and desorption behaviour towards the selected organic pollutants. It was observed that, in general, all natural building materials showed very low, or even zero, VOC emissions. In the case of formaldehyde, this organic pollutant was found to be emitted by the wood-based panels due to the formaldehyde-based resins used to glue the wood fibres. In the case of coated wood panels, the resin impregnated paper coating was shown to act as a barrier to formaldehyde emission and as a result this showed lower emission levels compared to an equivalent uncoated material. With regard to the adsorption and desorption behaviour it was observed that highly porous materials such as lime mortar and MDF panels have good capacity to remove VOCs and formaldehyde from the indoor air due to their high surface area. They allow the diffusion of the organic pollutants through their bigger pores. Natural wool, classed as an insulation material, showed good affinity to adsorb formaldehyde due to chemisorption by the proteins present in the fibres. The later stages of this research involved the investigation of the adsorption/desorption behaviour of newly developed natural building materials incorporating bio-based additives with optimised capacity to remove VOCs from the air. The incorporations were as follows: walnut shell within MDF panels; hemp sheaves, pumice and brick powder within clay-based plasters; and cellulose flakes, natural wool and photocatalytic TiO2 particles within lime mortar. The combination of two materials was also used because of the affinity of each material with different VOCs, for example the incorporation of natural wool in a lime mortar formulation. The outcomes of this research demonstrate that, if careful consideration is given to materials selection when constructing a new building or during a refurbishment process, the old judgment “building materials are the main contributors to a poor indoor air quality” is not true. This is achieved by selecting materials with low- or zero-VOC emissions and with the capacity to remove organic pollutants from the indoor air. Therefore, these materials contribute to a better indoor air quality by releasing low or negligible emissions and by facilitating the removal of airborne pollutants.

Les composés organiques volatils oxygénés (COVOs) sont des espèces chimiques importantes de l’atmosphère. Ils incluent, par exemple, les alcools aliphatiques, les aldéhydes, les cétones et les acides organiques. Dans la troposphère libre, l’abondance des COVOs est plus importante que celle des hydrocarbures non méthaniques et leur réactivité globale avec OH est comparable avec celle du méthane. En revanche le méthane est présent à une concentration plus élevée. La dégradation des COVOs dans l’atmosphère s’effectue soit par la réaction avec le radical OH, soit par photolyse. La dégradation des COVOs produit des radicaux libres qui vont influencer la capacité oxydante de l’atmosphère, les concentrations en oxydes d’azotes, en radical OH et en ozone troposphérique. L’ozone est le troisième plus important gaz à effet de serre dans l’atmosphère et est l’un des composants toxiques principaux des pollutions urbaines et intervient donc dans des problèmes environnementaux graves comme le réchauffement climatique et la dégradation de la qualité de l’air. L’objectif de ce travail est de contribuer à la compréhension du comportement atmosphérique de quelques COVOs en mesurant leurs paramètres cinétiques et photochimiques apportant des donnés afin de permettre la réalisation de modélisations informatiques et l’amélioration de la connaissance des mécanismes chimiques ayant lieu dans l’atmosphère
Oxygenated volatile organic compounds (OVOCs) are important constituents of the atmosphere. They include, e.g., aliphatic alcohols, aldehydes, ketones, and organic acids. In the free troposphere, the abundance of OVOCs is higher than that of the non-methane hydrocarbons and their overall reactivity with OH is comparable with that of methane, in contrast that methane is present in much higher concentration. Degradation of OVOCs in the atmosphere takes place via the reaction with OH radicals and, in the case of photochemically active molecules, via photolysis. Free radicals are formed in the photooxidative degradations of the oxygen containing organics which basically determine the oxidative capacity of the atmosphere, the transformation of nitrogen oxides and the concentration of OH radicals and tropospheric ozone. Ozone is the third most important greenhouse gas in the atmosphere, it is one of the toxic components of urban smog and so it is related to such grave environmental problems as global warming and the quality of air. The aim of this work is to contribute to the understanding of the atmospheric behaviour of a few OVOCs by measuring their kinetic and photochemical parameters. One of the major goals of a laboratory basic research in atmospheric chemistry is to provide kinetic and photochemical data for computer modelling and to deduce atmospheric transformation mechanisms in the case of some important chemicals

Oxygenated Volatile Organic Compounds (OVOCs) are low molecular weight (Cl-C3 compounds), volatile species that include alcohols, aldehydes and ketones. They are ubiquitous throughout thetroposphere where they alter the oxidative capacity of the atmosphere and influence the global ozone budget. The role of the ocean in the cycling of OVOCs remains largely unanswered due to a paucity of water measurements. Thisis . partly due to analytical difficulties in extracting these labile species from solution. Their presence at trace (nanomolar) concentrations and their high solubility makes efficient extraction from solution challenging. This thesis reviews the global importance and the current understanding of the OVOCs and highlights the uncertainty created from a paucity of oceanic measurements. It also details the available analytical capabilities for analysing these species, both in air and water to provide a platform from which to start method development. Developmental work was undertaken in order to design and validate two separate analytical techniques for the extraction of OVOCs from seawater: I) A Membrane Inlet - Proton Transfer Reaction / Mass Spectrometer (MI-PTRlMS) was optimised for the quantification of methanol, acetaldehyde and acetone in seawater, 2) a Purge andTrap- Gas Chromatography / Flame Ionisation Detection (P&T-GCIFID) system was developed for the extraction of ethanol, l-propanol, 2-propanol, propanal, acetone and acetaldehyde. Their independent capabilities are discussed as well as the advantages of their simultaneous use to provide maximum information regarding OVOC content within a sample. These techniques were deployed on two research cruises to as~ess the importance of an upwelling region and also to determine the spatial variability of both the concentration and flux of OVOCs in the Atlantic Ocean. The methods that have been developed during this research have increased the available data on OVOC concentrations in seawater and have shown that the ocean is important in the cycling of these trace gases.

The thesis focuses on ‘green’ sample preparation techniques that utilise minimal or no organic solvents thereby producing negligible volumes of organic waste, to ensure safety both to user and the environment. Volatile compounds were extracted and pre-concentrated from Kgalagadi desert truffles (kalaharituber) by headspace solid phase microextraction (HSSPME) and supercritical fluid extraction (SFE). PHWE was employed for the extraction of amino acids and fatty acids. Subsequent analysis of volatile compounds was carried out by gas chromatography coupled with mass spectrometry. Four types of HS-SPME fibers (PDMS 100 μm, PDMS 7 μm, Polyacrylate 85 μm, CAR/DVB/PDMS 50/30 μm) were evaluated. A total of 24 volatile compounds with a molecular weight range from 110 to 354, the most prominent peak being 2-t-Butyl-2,3-dimethyl-3-buten-1-ol (C₁₀H₂₀O, MW 156) were detected after sampling with a PDMS 100 μm fiber. Less volatile compounds were detected after SFE with CO2. A total of 16 amino acids were identified while 17 fatty acids (MW from 132.12 to 367.49) were also identified. The characteristic profile of the Kgalagadi desert truffle was found to contain mainly fatty acid methyl esters and unsaturated aliphatic hydrocarbons. The most prominent compound peaks identified were; 2-t-butyl-2,3-dimethyl- 3-buten-1-ol, disulfide, ethyl benzoic acid 2-4-dhydroxy-3,6-dimethyl-methyl ester, 8,11- octadecanoic acid methyl ester, benzoic acid, 2,4-dihydroxy-3,6-dimethyl-methyl ester, isoquinoline, 1 butyl-3,4-dihydro and 3-heptanone, 6 methyl. Optimization results indicated that fresh slices from the heart of truffles were the best to use for HS-SPME-GCMS volatile compound analysis as they showed a higher sensitivity

In this study the development of an improved electrochemical fuel cell sensor for the detection of low-levels of formaldehyde vapour is described. Current fuel cell sensors used in the commercial Formaldemeter™ instrument lack sensitivity, respond to methanol, and show an interference response to humidity. For the detection and accurate determination of low-level concentrations of formaldehyde an improvement in these characteristics is essential. Two routes were investigated to achieve these requirements. Firstly the oxygen reduction reaction at the cathode was replaced with that of a conducting polymer, polyaniline (P ANI). Before construction of the fuel cells the stability and open circuit behaviour of various P ANI films were investigated in order to assay their suitability as a cathode material in a fuel cell application. Based on these results various fuel cells containing P ANI as the cathode were prepared and incorporated into the FormaldemeterTM. The cells were then evaluated using a calibrated vapour stream. Fuel cells containing a Pt-black anode and a P ANI/SOlcoated Pt-black cathode in H2S04 electrolyte displayed a significant improvement in sensitivity, selectivity and a reduced humidity response. In addition a fast response time, excellent reproducibility and a long shelf life was demonstrated. It is proposed that a P ANI film coated on Pt-black behaves as a more stable electron sink for the cathodic reaction instead of the oxygen reduction reaction which is dependent on the diffusion of oxygen. The fast fuel cell response time is explained by the fast switching of PAN I « lOJls). In the second part of the work, the effect of changing fuel cell catalyst was investigated. Initially, the electrocatalytic activity of various noble metals and alloys electrodeposited on glassy carbon were investigated. Based on these results several fuel cell electrodes were prepared and characterised by SEM and EDAX. Fuel cells were then constructed and their performance evaluated. Cells made up of 50:50 % atomic weight ratio of platinum and palladium showed that while the fuel cell was active towards low levels of formaldehyde, its response to equivalent levels of methanol was very small.

Les composés organiques carbonylés et les BTEX (Benzène, Toluène, Éthylbenzène et Xylènes) représentent une classe importante de composés organiques volatils dans l’atmosphère. Ils sont émis par des sources anthropogénique et biogéniques. Leur dégradation atmosphérique conduit à la formation d’ozone, de phooxidants et d’aérosols organiques affectant ainsi la qualité de l’air aux échelles locales et régionales ainsi que la santé humaine. Il est donc important de mesurer leurs concentrations et évaluer leur devenir atmosphérique. Dans la présente thèse, nous avons conduit une étude systématique qui a permis de mesurer les concentrations de ces composés et identifier leurs sources à Pékin (Juillet 2008-Août 2010) et évaluer l’importance des caractéristiques météo. Nous avons aussi mené des études sur la dégradation atmosphérique de trois formates (isoproyle, isobutyle et n-propyle) en utilisant la chambre de simulation atmosphérique d’ICARE (CNRS, Orléans)
Carbonyls and BTEX (Benzene, Toluene, Ethylbenzene, and Xylenes) represent an important class of VOCs (volatile organic compounds) in the atmosphere. They are emitted into the atmosphere through anthropogenic and biogenic sources. Their atmospheric degradation leads to the formation of ozone, photooxidants and organic aerosols affecting the air quality at the local and regional scales and human health. It is, hence, of importance to measure their atmospheric concentrations and investigate their fate. In the present thesis, we have conducted a systematic measurement study of carbonyls and BTEX in Beijing during the period of Jul 2008-Aug 2010 in order to evaluate their ambient levels, possible sources and the influence of characteristic weather conditions. In a separate work, we performed a series of experimental studies on the OH-initiated oxidation of isopropyl formate, isobutyl formate, and n-propyl isobutyrate using the ICARE-CNRS (Orleans) simulation chamber from which we derived the product yields. The data obtained are presented and discussed

Volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) constitute important classes of indoor contaminants. Emissions of VOCs and SVOCs from myriad building materials and consumer products cause high indoor concentrations with health risks that may be orders-of-magnitude greater than outdoors. The need to control VOC and SVOC emissions from interior materials and thereby reduce indoor concentrations is made more urgent by the prevailing drive for air-tight, energy efficient buildings. To develop low-emission products, emission rates are usually measured in emission chambers. However, there are three significant problems associated with chamber tests: (1) VOC emissions testing procedures of individual laboratories are frequently subject to error and uncertainty; (2) SVOC emissions testing in chambers is extremely difficult and time-consuming, and also subject to error and uncertainty; and (3) chamber tests provide little insight into the mechanisms controlling emissions. This research aimed to solve these problems by developing reference materials for VOC and SVOC emissions testing. Formaldehyde was studied separately from other VOCs because of its unusual properties. Emission mechanisms, and the related modeling approaches for predicting emissions, were investigated by reviewing the literature and performing chamber studies. Based on the internally controlled VOC and formaldehyde emission mechanisms, diffusion-controlled reference materials, which mimic real sources, were created for VOCs and formaldehyde. Approaches for developing externally controlled reference materials for SVOC emissions testing were also explored. Appropriate mechanistic models can predict the true emission rates of the reference materials and therefore provide reference values to validate emissions testing results and certify procedures of individual laboratories. The potential of a solid phase microextraction (SPME) method was also evaluated and found to be a promising technique that can be used in chamber tests to simplify and improve sampling and analytical procedures.T his research elucidates the mass-transfer mechanisms of VOC and SVOC emissions and provides practical approaches for developing reference materials for emissions testing. The fundamental understanding and methodological advances will enhance indoor air quality science, improve the emissions testing industry, and provide a sound basis on which to develop standards and regulations.
Ph. D.

Chau Wing-sze.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2004.
Includes bibliographical references (leaves 238-262).
Abstracts in English and Chinese.
Abstract (in English) --- p.i
Abstract (in Chinese) --- p.iv
Acknowledgement --- p.vi
Contents --- p.ix
List of Figures --- p.xv
List of Tables --- p.xvi
Chapter 1. --- Introduction --- p.1
Chapter 1.1 --- Introduction --- p.1
Chapter 1.2 --- Introduction of samples --- p.2
Chapter 1.3 --- Flavor of Chinese salted-dried fish --- p.4
Chapter 1.4 --- Objectives of the study --- p.5
Chapter 2. --- Literature review --- p.7
Chapter 2.1 --- Introduction --- p.7
Chapter 2.2 --- Volatile compounds in fresh fish --- p.8
Chapter 2.2.1 --- Groups of volatile compounds --- p.9
Chapter 2.2.2 --- Variation in fresh fish flavor --- p.12
Chapter 2.2.2.1 --- Intrinsic factor --- p.12
Chapter 2.2.2.2 --- Environmental factors --- p.15
Chapter 2.2.2.3 --- Post harvest conditions --- p.16
Chapter 2.3 --- Fish preservation --- p.17
Chapter 2.3.1 --- Preservation methods --- p.18
Chapter 2.3.1.1 --- Drying --- p.19
Chapter 2.3.1.2 --- Salting --- p.19
Chapter 2.3.1.3 --- Fermentation --- p.21
Chapter 2.3.2 --- Theory of drying and salting --- p.21
Chapter 2.3.3 --- Different protocols in the world --- p.23
Chapter 2.3.3.1 --- European methods --- p.24
Chapter 2.3.3.2 --- Southeast Asian methods --- p.25
Chapter 2.3.3.3 --- Thai methods --- p.27
Chapter 2.3.3.4 --- Chinese method --- p.28
Chapter 2.3.3.5 --- Local method --- p.29
Chapter 2.3.4 --- Consumption procedures --- p.31
Chapter 2.3.5 --- Advantages of drying besides preservation --- p.31
Chapter 2.3.5.1 --- Convenience in transportation --- p.32
Chapter 2.3.5.2 --- Flavorization --- p.32
Chapter 2.3.5.3 --- Nutritional values --- p.33
Chapter 2.4 --- Flavor of salted-dried fish --- p.34
Chapter 2.4.1 --- Taste of salted-dried fish --- p.35
Chapter 2.4.2 --- Aroma of salted-dried fish --- p.35
Chapter 2.4.3 --- Flavor of Chinese salted-dried fish --- p.37
Chapter 2.4.4 --- Parameters affect the flavor and quality of salted-dried fish --- p.38
Chapter 2.4.4.1 --- Freshness --- p.38
Chapter 2.4.4.2 --- Temperature --- p.39
Chapter 2.4.4.3 --- Post harvest freezing and thawing --- p.40
Chapter 2.4.4.4 --- Gutting --- p.42
Chapter 2.4.4.5 --- Salt quality --- p.43
Chapter 2.5 --- Biological deterioration in salted fish --- p.46
Chapter 2.6 --- Salted-dried fish in Hong Kong --- p.47
Chapter 3. --- Materials and methods --- p.55
Chapter 3.1 --- Materials --- p.55
Chapter 3.1.1 --- Abbreviation of names of samples --- p.55
Chapter 3.1.2 --- Handling of samples --- p.56
Chapter 3.2 --- Method --- p.58
Chapter 3.2.1 --- Modified Simultaneous steam distillation-solvent extraction (SDE)-Steaming --- p.58
Chapter 3.2.2 --- Concentration --- p.59
Chapter 3.2.3 --- Gas chromatography-mass spectrometry (GC-MS) --- p.59
Chapter 3.2.4 --- Compound identification --- p.60
Chapter 3.2.5 --- Quantification of compounds --- p.60
Chapter 3.2.6 --- Moisture analysis --- p.62
Chapter 3.2.7 --- Texture analysis --- p.62
Chapter 3.2.8 --- Statistical analysis --- p.63
Chapter 3.2.9 --- OAV calculation --- p.64
Chapter 4. --- Results and Discussion --- p.66
Chapter 4.1 --- Threadfin --- p.66
Chapter 4.1.1 --- Overall description of volatile compounds in salted-dried threadfin --- p.66
Chapter 4.1.2 --- Characteristic compounds in delayed (D) groups of samples --- p.68
Chapter 4.1.3 --- Characteristic compounds in regular (R) groups of samples --- p.70
Chapter 4.1.4 --- Common compounds found in the eight groups of samples --- p.71
Chapter 4.1.5 --- Comparison of common compounds among individual groups of salted-dried fish --- p.78
Chapter 4.1.5.1 --- Comparison between delayed and regular salting methods --- p.78
Chapter 4.1.5.2 --- Comparison between locations of purchase --- p.80
Chapter 4.1.5.3 --- Comparison between samples from different years (2000 and 2001) --- p.81
Chapter 4.1.6 --- Exclusive compounds found in delayed salted (D) or regular salted (R) fish --- p.83
Chapter 4.1.7 --- Conclusion of threadfin --- p.84
Chapter 4.2 --- White herring --- p.85
Chapter 4.2.1 --- Overall description of volatile compounds in salted-dried white herring --- p.85
Chapter 4.2.2 --- Characteristic compounds in delayed (D) groups of samples --- p.87
Chapter 4.2.3 --- Characteristic compounds in regular (R) groups of samples --- p.88
Chapter 4.2.4 --- Common compounds found in the eight groups of samples --- p.89
Chapter 4.2.5 --- Comparison of common compounds among individual groups --- p.94
Chapter 4.2.5.1 --- Comparison between delayed and regular salting methods --- p.94
Chapter 4.2.5.2 --- Comparison between locations of purchase --- p.96
Chapter 4.2.5.3 --- Comparison between samples from different years --- p.97
Chapter 4.2.6 --- Conclusion of white herring --- p.98
Chapter 4.3 --- Pawak croaker --- p.100
Chapter 4.3.1 --- Overall description of volatile compounds in salted-dried pawak croaker --- p.100
Chapter 4.3.2 --- Characteristic compounds in delayed (D) groups of samples --- p.102
Chapter 4.3.3 --- Characteristic compounds in regular (R) groups of samples --- p.105
Chapter 4.3.4 --- Common compounds found in the eight groups of samples --- p.106
Chapter 4.3.5 --- Comparison of common compounds among individual groups of salted-dried fish --- p.111
Chapter 4.3.5.1 --- Comparison between delayed and regular salting methods --- p.111
Chapter 4.3.5.2 --- Comparison between locations of purchase --- p.114
Chapter 4.3.5.3 --- Comparison between two batches of samples from different years --- p.115
Chapter 4.3.5.4 --- Characteristic compounds of pawak croaker --- p.117
Chapter 4.3.6 --- Conclusion of pawak croaker --- p.118
Chapter 4.4 --- Overall comparison of compounds of the three species --- p.120
Chapter 4.4.1 --- Introduction --- p.120
Chapter 4.4.2 --- Comparison of three species of fishes --- p.121
Chapter 4.4.2.1 --- Delayed- and regular- smell contributors --- p.122
Chapter 4.4.3 --- The difference among the groups of fishes --- p.123
Chapter 4.4.3.1 --- Effect of different body compositions of fishes --- p.124
Chapter 4.4.3.1.1 --- Lipid originated volatile aldehydes --- p.125
Chapter 4.4.4 --- Common compounds detected in all three species of salted-dried fishes --- p.126
Chapter 4.4.4.1 --- Compounds with high calculated aroma values (OAV) --- p.127
Chapter 4.4.4.2 --- Compounds with low calculated aroma values (OAV) --- p.130
Chapter 4.4.5 --- Effect of treatment methods --- p.132
Chapter 4.4.6 --- Effect of locations of collection of samples on the composition --- p.134
Chapter 4.4.7 --- Effect of time of collection of samples on the composition --- p.135
Chapter 4.4.8 --- Characteristic compounds found only in one species --- p.135
Chapter 4.4.8.1 --- Characteristic compounds of threadfin --- p.136
Chapter 4.4.8.2 --- Characteristic compounds of white herring --- p.136
Chapter 4.4.8.3 --- Characteristic compounds of pawak croaker --- p.138
Chapter 4.5 --- Texture --- p.139
Chapter 4.5.1 --- Introduction --- p.139
Chapter 4.5.2 --- Results and Discussion --- p.141
Chapter 4.5.2.1 --- Comparison between regular and delayed salted-dried fishes --- p.141
Chapter 4.5.2.1.1 --- Effects of enzymatic reaction --- p.141
Chapter 4.5.2.1.2 --- Effects of fermentation --- p.142
Chapter 4.5.2.1.3 --- Frozen period before regular salting --- p.143
Chapter 4.5.2.2 --- Comparison between raw and steamed salted-dried fishes --- p.145
Chapter 4.5.2.3 --- Moisture content of salted-dried fishes --- p.146
Chapter 4.5.3 --- Conclusion --- p.147
Chapter 5. --- Conclusion and Significance --- p.233
Chapter 5.1 --- General conclusion --- p.233
Chapter 5.2 --- Significance of the study --- p.235
References --- p.238
Appendix I --- p.263
Appendix II --- p.264