Добірка наукової літератури з теми "Gas chromotography-mass spectrometry"

In this study,a total of 120 agriculture soils samples,theirty two Actinomycetes isolates were isolated from ten different locations in Babylon city which were purified several times on International Streptomyces project-2 agar medium (ISP-2). All these isolates were tested for antibacterial activity by primary and secondary screening test against gram positive pathogenic bacteria (Staphylococcus albus,Staphylococcus aureus,and Streptococcus pyogenes) and gram negative pathogenic bacteria (Klebsillae pnemoniae,Escherichia coli,Pseudomonas aerouginosa,Seratia marcescens and Aeromonas hydrophila), televe isolates were showed antibacterial activity against these bacteria. Bacterial extraction of three of actinomycetes isolates which showed high antibacterial activity,the isolates (No.3:MS.A.21,No.8:AG.A.72,No.10:R.A.98) were chemicly characterized by gas chromotography techniques (GC-Mass) to detect volatile organic compounds.Five components were identified in the ethyl acetate bacteria extract. The compounds were Acetic acid (58.42%) as the major component followed by 2-Butanone,3-hydroxy (21.23%),Butanoic acid,2-methyl (8.76%),2, 3-Butanediol, [R- (R*, R*)] (7.75%) and last couponed propanoic acid, 2-methyl (3.84%) respectively. Figure (4-1) shows the mass spectrum and structures of the identified components.

Lipids are important for the structural and physiological functions of neuronal cell membranes. Alterations in their lipid composition may result in membrane dysfunction and subsequent neuronal deficits that characterise various disorders. This study focused on profiling lipids of aged and LPS-treated rat brain and liver tissue with a view to explore the effect of atorvastatin in neuroinflammation, and examining lipid changes in different areas of rat brain of the Flinders Sensitive Line (FSL) rats, a genetic model of depression. Lipids and other analytes extracted from tissue samples were analysed with proton nuclear magnetic resonance spectroscopy (1H-NMR), gas chromatography (GC) and liquid chromatography-tandem mass spectroscopy (LC/ESI-MS/MS). Changes in the lipid profiles suggested that brain and liver responded differently to ageing and LPS-induced neuroinflammation. In the aged animals, n-3 PUFA were reduced in the brain but were increased in the liver. However, following treatment with LPS, these effects were not observed. Nevertheless, in both models, brain concentration of monounsaturated fatty acids was increased while the liver was able to maintain its monounsaturated fatty acid concentration. Atorvastatin reversed the reduction in n-3 PUFA in the aged brain without reducing brain and liver concentration of cholesterol. These findings further highlight alterations in lipid metabolism in agerelated neuroinflammation and show that the anti-inflammatory actions of atorvastatin may include a modulation of fatty acid metabolism. When studying the FSL model, there were differences in the lipid profile of different brain areas of FSL rats compared to Sprague-Dawley controls. In all brain areas, arachidonic acid was increased in the FSL rats. Docosahexaenoic acid and ether lipids were reduced, while cholesterol and sphingolipids were increased in the hypothalamus of the FSL rats. Furthermore, total diacylglycerophospholipids were reduced in the prefrontal cortex and hypothalamus of the FSL rats. These results show differences in the lipid metabolism of the FSL rat brain and may be suggestive of changes occurring in the brain tissue in depression.

Lipids are important for the structural and physiological functions of neuronal cell membranes. Alterations in their lipid composition may result in membrane dysfunction and subsequent neuronal deficits that characterise various disorders. This study focused on profiling lipids of aged and LPS-treated rat brain and liver tissue with a view to explore the effect of atorvastatin in neuroinflammation, and examining lipid changes in different areas of rat brain of the Flinders Sensitive Line (FSL) rats, a genetic model of depression. Lipids and other analytes extracted from tissue samples were analysed with proton nuclear magnetic resonance spectroscopy (1H-NMR), gas chromatography (GC) and liquid chromatography-tandem mass spectroscopy (LC/ESI-MS/MS). Changes in the lipid profiles suggested that brain and liver responded differently to ageing and LPS-induced neuroinflammation. In the aged animals, n-3 PUFA were reduced in the brain but were increased in the liver. However, following treatment with LPS, these effects were not observed. Nevertheless, in both models, brain concentration of monounsaturated fatty acids was increased while the liver was able to maintain its monounsaturated fatty acid concentration. Atorvastatin reversed the reduction in n-3 PUFA in the aged brain without reducing brain and liver concentration of cholesterol. These findings further highlight alterations in lipid metabolism in agerelated neuroinflammation and show that the anti-inflammatory actions of atorvastatin may include a modulation of fatty acid metabolism. When studying the FSL model, there were differences in the lipid profile of different brain areas of FSL rats compared to Sprague-Dawley controls. In all brain areas, arachidonic acid was increased in the FSL rats. Docosahexaenoic acid and ether lipids were reduced, while cholesterol and sphingolipids were increased in the hypothalamus of the FSL rats. Furthermore, total diacylglycerophospholipids were reduced in the prefrontal cortex and hypothalamus of the FSL rats. These results show differences in the lipid metabolism of the FSL rat brain and may be suggestive of changes occurring in the brain tissue in depression.

Volatile phenols are responsible for some off-odours in wine, for example, the objectionable smoky, ashy notes associated with smoke taint and the sweaty, horsey, barnyard character associated with Brettanomyces. Various strategies have been evaluated for use by the wine industry to ameliorate wines with excessive levels of volatile phenols. The current project aimed to explore cyclodextrins (CDs) as a novel approach to amelioration. CDs are a group of glucose-based oligosaccharides, which are characterised by their truncated cone structure, and hydrophilic outer surface and hydrophobic inner cavity. These properties offer CDs the ability to form inclusion complexes with hydrophobic guest molecules in aqueous environments, which has been exploited by various industries, including the food and beverage industries. Chapter 1 comprises a review of literature concerning smoke taint and CDs. The limited knowledge regarding interaction between CDs and wine constituents is discussed, and then the research aims are stated. Chapter 2 comprises a study into the formation of inclusion complexes between CDs and volatile phenols in model wine, confirmed by sensory and nuclear magnetic resonance (NMR) analysis techniques. A limitation associated with conventional headspace gas chromatography mass spectrometry (HS GC-MS), namely the interaction of CD with the normalising standard is identified. A new HS GC-MS method is therefore developed to address this issue by isolating the normalising standard from the sample mixture as an additional liquid phase that still shares the same headspace during sample extraction. The inclusion of volatile phenols by CDs is then characterised using the validated method, demonstrating the reduction in headspace residuals of volatile phenols, following the addition of CD. Chapter 3 explores the potential of CD polymers to remove volatile phenols from a model wine system. The preparation of hexamethylene diisocyanate (HDI) crosslinked CD polymers is described. Several parameters influencing the removal of volatile phenols by CD polymers are then characterised, for example, the time required to achieve adsorption equilibrium, isotherms (Langmuir and Freundlich models), adsorption capacity and reusability. A batch adsorption test described in this chapter achieved up to 77% removal of volatile phenols. Chapter 4 adopts the methods and materials developed in previous chapters, and describes the impact of CDs and CD polymers, when used as treatments for smoke taint, on wine parameters. The treatments were applied to smoke affected must at different stages of fermentation. Reductions in the headspace concentrations of volatile phenols was observed following treatment, but certain aroma compounds were also lost, based on HS GC-MS and sensory analysis. The potential for a CD polymer to remove volatile phenol glycoconjugates was also investigated. Chapter 5 summarises key findings from this thesis and discusses future directions for related research.
Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2018

Aroma is one of the most important quality attributes of bread or any food. It will determine whether the product will be tasted and eaten in the first instance and is a major factor in establishing acceptability and preference. The dominant preference by consumers of bread made from refined flour in contrast to whole wheat flour is at least in part due to the strong and different aroma of whole wheat bread. White wheats may have an advantage over red wheat in this regard according to some industry reports, but the science is extremely limited. The goal of this research was to add more science-based knowledge to this topic via the use of machine olfaction technology, specifically electronic (E) nose and gas chromatography combined with mass spectrometry (GC-MS). A state-of-the-art E-nose system (AlphaMOS FOX 3000) with metal oxide sensors (MOS) was used to capture aroma volatiles from crumb, crust and whole slices of breads made from sound Canadian Western Red Spring (CWRS) wheat as well as representative samples of two hard white wheats, viz. Snowbird, a cultivar belonging to the Canada Western Hard White Spring (CWHWS) class of wheat, and Platte, a U.S. Hard White Winter (HWW) wheat. The same CWRS wheat provided the base flour for all the breads. A commercial formula and size format was used to produce breads from four flours for the study, i.e. refined CWRS wheat, and three whole wheat flours comprising blends of 85% CWRS flour and 15% bran from CWRS wheat, Snowbird and Platte. As there was no established protocol in the literature to evaluate bread aroma by E-nose, one was developed. Five temperatures (35, 40, 45, 50 and 60°C) were tested along with two incubation times (5 and 10 min) and four sample sizes (0.05, 0.1, 0.25 and 0.50 g) of ground bread crumbs. Through optimization using E-nose software including principal component analysis, a procedure was adopted using 40 °C, 5 min incubation time and 0.05 g of sample to acquire MOS data from 12 sensors for crust, crumb and whole slices of refined and whole wheat breads. Multivariate analysis methods were used to evaluate the capabilities of the E-nose system to discriminate and correctly classify samples according to bread type. Data for analysis comprised approximately 24 samples each of crust, crumb and whole slices randomly selected from three loaves each of refined and the three whole wheat breads. Results varied according to the nature of the sample, i.e. crust, crumb or whole slices. For crusts, the greatest distinction in aroma was found between refined and whole wheat breads. Refined bread crust was correctly classified 67% of the time. When refined bread crust was misclassified, samples were confused with whole white wheat crust predominantly from Platte bread. For whole wheat bread crusts, the pattern of classification depended mainly on bran colour. Whole wheat bread crust samples had correct classification scores in the range 54-58%. When misclassified, whole wheat CWRS crust was equally confused with the aroma of crust of the white whole wheat breads, Platte and Snowbird. Whole wheat Platte crust tended to be misclassified with the counterpart white whole wheat Snowbird or refined bread crust. In contrast, Snowbird whole wheat crust tended to be misclassified as either its counterpart HW wheat Platte or whole CWRS wheat. Accordingly, Platte bread crust appeared to possess an aroma more in line with refined wheat bread as opposed to whole wheat bread. For bread crumb, the pattern of E-nose differentiation of samples was different. In this case, CWRS whole wheat bread aroma was clearly and perfectly distinguished from the crumb aroma of all the other breads, either whole white wheat or refined CWRS. The latter tended to cluster on its own, as might be expected, and had a correct classification score of 75%, with the balance of samples largely misclassified as Snowbird crumb. Whole wheat Platte and Snowbird bread crumb had identical correct classification scores of 42%, and were similarly confused with the other’s aroma (average 3 4% classified) or the aroma of refined wheat bread (average 21% classified). E-nose results for crumb indicated a clear distinction in aroma between the hard red and white wheats in this study. E-nose analysis of bread samples representing whole slices produced results that provided unsatisfactory discrimination among bread types likely due to the blending of the different aromas of constituent crust and crumb. For whole slices, discrimination between refined and whole wheat breads was substantially lower than that for either crust and crumb samples. Based on this result, analysis of samples that combine both crust and crumb is not recommended for sensory analysis of bread, whether by instruments or human sensory panel. Further understanding of the differences between different types of bread made from refined wheat flour and whole wheat, and how the inclusion of bran from red and white-grained wheats modifies the composition and content of volatile and non-volatile compounds in crust and crumb was determined by gas chromatography-mass spectrometry (GC-MS). In total, 50 compounds were found, the greater majority of which have been previously reported in bread. Major Maillard reaction compounds like furfural, 2-furanmethanol, pyranone, maltol and 5-hydroxymethyl- 2-furancarboxaldehyde were present in highest concentration in whole CWRS bread. Significantly fewer compounds were found in the crust and crumb of CWRS refined wheat bread compared to the other whole wheat breads. In contrast, whole CWRS bread crumb and crust had the highest number of compounds, and in considerably higher total concentration compared to the other two whole white wheat breads, Snowbird and Platte. The higher concentration and number of compounds in whole CWRS bread was attributed to the wheat bran fraction. White whole wheat breads, Snowbird and Platte, had a total number of compounds in crust and crumb approximately intermediate between refined and whole CWRS bread, although Platte whole wheat bread crust was closer to refined bread crust in compound numbers. In terms of total compound concentrations, crust and crumb samples of the whole white breads were clearly more similar to refined CWRS bread, and in the case of whole wheat Platte bread crust, compound concentrations were much lower. On the whole, these aggregate totals of compound numbers and concentrations by GC-MS mirrored the discrimination and classification results obtained by E-nose, and supported the contention that whole wheat bread made with white wheat bran was milder in aroma compared to bread formulated using red wheat bran. While the number of samples of red and white wheats were very few in this study, results support the contention that different wheat genotypes and specifically, the bran tissue of these genotypes, contain differences in compound composition and/or concentration which when processed by breadmaking, manifest volatiles characteristic of those genotypes even between genotypes possessing the same colour of bran. E-nose instrumentation appears to be very capable of accommodating these sorts of complex tasks on fresh bread. It would be highly beneficial in future research to carry out similar studies in parallel with a human sensory panel, and ideally with many more genotypes of red and white grained wheat with an aim to firmly establish the relative superiority of particular genotypes to produce whole wheat bread with aroma profiles more similar to those of white pan bread. The long term goal of such studies would be to foster increased consumption of whole wheat products and constituent bioactive compounds which confer favourable health benefits in the general population.