Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 20 for “"Pyrazines"”.
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Evaluation of Initial Flavor Fade in Fresh Roasted Peanuts using Gas Chromatography-Flame Ionization Detection, Gas Chromatography-Olfactometry, Sensory Analysis, and Chemosensory Techniques
… The carbonyl-amine reaction yields a variety of pyrazines with positive flavor attributes. Initial flavor notes were explored through sensory work, Gas Chromatography-Olfactometry, and chemical analysis. The fresh roasted volatiles produced from roasted peanuts and the aldehydes resulting from …
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The synthesis and reactivity of 7-azaindolizines.
… reaction between suitably substituted methylpyrazines and a-bromoketones. The structures of the products obtained have been confirmed spectroscopically (mainly by pmr spectroscopy) and elemental analysis. Examination of the pmr spectra of 7-azaindolizines in trifluoroacetic acid showed solely …
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Structure-Activity Relationship Studies of Imidazo[4,5-b]pyrazine Derivatives as Mitochondrial Uncouplers and their Potential in the Treatment of Obesity
… method for the synthesis of 1H-imidazo[4,5-b]pyrazines from [1,2,5]oxadiazolo[3,4-b]pyrazines is herein disclosed. In the presence of Fe, Yb(OTf)3, and the desired electrophile partner, in situ reduction of the oxadiazole fragment followed by cyclization afforded imidazolopyrazines in moderate …
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Key volatile and nonvolatile off-flavor characterization for nine different hemp protein powders
… more volatiles such as alcohols, furan, and pyrazines while the whole seed proteins powder contained more aldehydes, carboxylic acids, and terpenes.
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Characterization of biofuel from diatoms via hydrothermal liquefaction
… nitrogen-containing compounds, such as pyrazines, according to GC-MS analysis. The inorganic frustules remained in the solid residue, unchanged after the hydrothermal process, with small amounts of organic matter attached, as revealed by SEM observation and FT-IR characterization. The …
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Development of Catalytic Enantioselective Minisci-type Reactions
… Minisci-type reaction of pyrimidines and pyrazines. The final research section addresses the possible degradation pathway observed in our initial hydroxyalkylation strategy by controlling reaction temperature and a crucial switch of photocatalytic system through consideration of the …
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Synthesis and stabilization of selected heterocyclic aroma compounds
Alkylpyrazines and alkanone substituted pyrrolines are heterocyclic compounds and are predominant odorants in various foods in which they provide pleasant nutty and roasty aroma characteristics. This study describes the development of technologies for the accurate and precise quantitation of flavor …
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Ruthenium Hydride Catalyzed Silylvinylation of Alkynes
… for the synthesis of imidazo[4,5-b]pyridines and pyrazines using palladium catalyzed amidation of 2-chloro-3-aminopyridines is described. The process utilizes Xantphos and a binary solvent system comprised of 1,4-dioxane and tert-amyl alcohol. The improved conditions were extended to provide a …
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Development of Pd Catalyzed Amidations & Applications to the Synthesis of Heterocycles
… facile synthesis of imidazo[4,5-b]pyridines and -pyrazines is described using a Pd-catalyzed amide coupling reaction. This reaction provides quick access to products with substitution at N1 and C2. A model system relevant to the natural product pentosidine has been demonstrated, as well as the …
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Effects of time and temperature during melanging on the volatile profile of dark chocolate
… for their particular relevance to the system. Pyrazines displayed the strongest pattern of any annotated chemical class. As a rule, these compounds started with moderate to high abundance at 0 hours and decreased to extremely low levels by 24 hours. However, most classes of chemical compounds …
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Characterization of aroma components of raw and roasted almonds and the effect of the oxidative state of the nut on roasted flavor formation
… oil roasted almonds. These compounds were mainly pyrazines, pyridines, pyrrolines, aldehydes and furanones. Aroma changes of stored raw (SR) and stored raw-then-roasted (SRTR) almonds were investigated by gas chromatography-olfactometry (GCO) and aroma extract dilutions analysis (AEDA) and GC-mass …
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Rapid and Green Volatilomics of Roasted Hazelnuts: Comparative Multiplatform Analysis and Advanced Data Mining
… evaluating the IMS detector response to alkyl pyrazines, which are key compounds for hazelnut flavor and roasting markers; (iii) developing a quantitative approach for VOCs in hazelnut paste; (iv) implementing an automated peak detection workflow to extend GC-IMS application to untargeted …
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Understanding consumer liking of beef with particular reference to flavour
… quantities of Strecker aldehydes, n-ketones and pyrazines. Differences in lipid content may explain the differences in the quantity of volatile compounds, which was clearly indicated using principal component analysis. These data indicated that modified atmosphere packaging induced generation of …
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Novel P,N-Ligand Stabilized Transition Metal Complexes as Efficient Catalysts for Organic Syntheses
… substrates such as pyridimidines, pyrazines, pyridazines and even pyridines are perfectly tolerated.
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Comprehensive Mapping of Volatile Organic Compounds in Fruits
… 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 …
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Impact of roasting on the physicochemical characteristics of cacao beans and dark chocolate flavor profile
… observed in furanones, Strecker aldehydes, and pyrazines, which presented higher values in roasted chocolate. Additionally, volatiles developed during fermentation and drying, such as acetic acid, were preserved in minimally processed (unroasted) chocolate. Roasting also impacted physicochemical …
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Inhibitory effect of edible films and coatings containing selected amino acids on the formation of 2-amino-1-methyl-6-phenylimidazo[4-5-b]pyridine (PhIP) in pan-fried chicken breasts
… an increase in several aroma compounds such as pyrazines in the coated chicken. Moreover, no significant differences (p>0.05) was shown between cooking loss percentage, color parameters, texture profile and tenderness of chicken with PS-0.25% coating and chicken without coating. Overall, the …
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Sensory directed determination of odor important components of natural (raw) and roasted pecan oil
… the importance of heterocyclic volatiles such as pyrazines, pyrrolines, furanones, and lactones that possess nutty, popcorn-like, caramel-like, and creamy, coconut-like aromas, as well as volatile aldehydes and ketones that possess malty and buttery aromas in RPO, all of which can be attributed to …
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Investigation of New Zealand Sauvignon Blanc Wine Using Trained Sensory Panels
ABSTRACT A core tool of sensory science is the use of trained descriptive panels. This research describes an investigation into the role of motivation in the performance of trained panels and the use of a trained panel to develop a better understanding of the perception of Sauvignon blanc wines. …
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Chemie polynitrovaných heterocyklických sloučenin
Byla zpracována rešerše na téma polynitrované heterocyklické sloučeniny. Jedná se o sloučeniny se schopností detonace, způsobené zejména přítomností nitroskupin, které jsou navázány na atomy uhlíku jejich cyklu. Tato práce se zabývá nejznámějšími zástupci jednotlivých skupin tohoto typu látek od …