The aim of this study was to investigate the amino acid composition and the amount of individual glycation compounds in hot trub formed during boiling of wort prepared from different malts. Compared to the initial amino acid composition of the used malts, some Maillard reaction products (namely MG-H1, pyrraline) and hydrophobic amino acids (leucine, isoleucine, valine, phenylalanine) accumulated in the hot trub, whereas hydrophilic amino acids remained in the boiled wort. For MG-H1, a threefold increase was observed during wort boiling, whereas the other Maillard reaction products, namely CML, CEL, pyrraline and maltosine increased only slightly (1.1–2-fold). Furosine as a hallmark for peptide-bound Amadori compounds showed a small decrease. The results suggest that mainly glycated amino acids derived from small dicarbonyl compounds such as methylglyoxal and glyoxal are formed during wort boiling. Furthermore, the studies indicate that the modification of the protein structure as a result of the Maillard reaction has an influence on the hydration of the denatured proteins during the wort boiling process, thus affecting the coagulation process and, therefore, precipitation of the hot trub. The work carried out contributes to the understanding of the chemical reactions influencing the amino acid and Maillard reaction product transfer from malt to beer.

Die artgerechte Erzeugung tierischer Lebensmittel hat einen großen Stellenwert bei Verbrauchern eingenommen. Zum Schutz der Verbraucher, werden analytische Verfahren benötigt, um Lebensmittel verlässlich zu authentifizieren. Von Schwarzenbolz et al. (2016) wurde ein Ansatz beschrieben, bei welchem über die Analyse von freien Maillard-Reaktionsprodukten (MRP) in tierischen Lebensmitteln, wie Milch und Milchprodukten, Aussagen über die Fütterung der Tiere mit thermisch behandelten Futtermitteln getroffen werden können. In der vorliegenden Arbeit wurde ein grundlegender Überblick über die Konzentrationen einzelner MRP in unterschiedlichen Futtermitteln für Milchkühe geschaffen, welcher eine Abschätzung der quantitativen Aufnahme von MRP über das Futter von Milchkühen erlaubt. Mithilfe von Untersuchungen zum Carry-over von MRP in verschiedenen Nutztieren erfolgten Abschätzungen zur Bioverfügbarkeit der MRP in den Nutztieren, wobei sich Unterschiede zwischen den untersuchten MRP Pyrralin, MG-H1 und CML zeigten. Erhitzungsexperimente und Modellinkubationen von Milch lieferten neue Erkenntnisse zur Bildung bzw. zum Abbau freier MRP während der Prozessierung von Milch zu Milchprodukten. Diese Ergebnisse können einen Beitrag zur Authentifizierung von tierischen Lebensmitteln leisten, da über die Konzentrationen von freien MRP in den Lebensmitteln Aussagen zum aufgenommenen Futtermittel und einer evtl. artgerechten, d.h. MRP-armen, Tierernährung getroffen werden können. Eine weitere Charakterisierung der Bioverfügbarkeit von MRP, insbesondere in Bezug auf individuelle Unterschiede, ist jedoch noch notwendig. [Schwarzenbolz U, Hofmann T, Sparmann N, Henle T (2016). J. Agric. Food Chem., 64, 5071-5078.]

Ce travail porte sur l'identification de la structure et des mécanismes de formation de quelques produits de Maillard non volatils, l'objectif principal étant de mieux connaître le rôle précurseur de la glutamine. Contrairement aux molécules volatiles, nos connaissances sur les composés non volatils sont assez peu étendues. De plus, la glutamine, de structure proche de celle de l'asparagine, possède deux atomes d'azote susceptibles de participer à la réaction de Maillard : l'α-amine et l'ammoniac issu de la lactamisation. Dans ce contexte, nous avons recherché, isolé et caractérisé les produits de Maillard non volatils susceptibles de se former lors du traitement thermique d'aliments riches en glutamine et en ammoniac. A l'aide de différents outils analytiques (HPLC, fluorescence, spectrométrie de masse, RMN

La recherche de substituts aux antioxydants alimentaires synthétiques (sulfites, BHA : di-tertio-butylhydroxyanisol et BHT : di-tertio-butyl-hydroxytoluène) utilisés contre l'oxydation des phénols et des lipides est actuellement très active en raison des effets allergènes et toxiques de ces additifs. Il a été montré que les produits de la réaction de Maillard (PRM) formés lors du chauffage de la cystéine et du glucose en milieu acide, sont de très puissants inhibiteurs du brunissement enzymatique des fruits et légumes du à l'oxydation des phénols catalysée par les polyphénoloxydases (PPO) en présence d'oxygène. Afin de pouvoir caractériser les composés inhibiteurs des PRM, ces systèmes modèles ont été simplifiés en un mélange de composés néoformés à partir de la réaction entre le HMF et la cystéine chauffée ou le sulfure d'ammonium. Ce mélange s'est révélé être environ trois fois plus efficace que les PRM pour inactiver la PPO de différentes origines végétales. La réaction de formation des composés inhibiteurs a été étudiée et une comparaison des pouvoirs antioxydants (tests AAPH° et DPPH°) et chélateurs du cuivre (test TMM) a été réalisée. Aux concentrations suffisantes pour prévenir le brunissement de purées de fruits et de légumes mesuré par des tests colorimétriques (L*, a*, b*), les produits néoformés, plus efficaces que les sulfites, n'ont montré aucun effet mutagène d'après les tests d'Ames réalisés sur les souches TA 98 et TA 102. Les lipoxygénases (LOX) catalysent l'oxydation des acides gras poly-insaturés. La méthodologie des plans d'expériences a permis la détermination des PRM ayant le plus fort pouvoir inhibiteur (PI) de l'activité LOX extraites du soja et de la farine de fève : les PRM issus du chauffage de la lysine et du glucose à 120 °C pendant 15 h montrent une inhibition non-compétitive irréversible de la LOX. De plus, ces PRM sont particulièrement stables au cours du temps de stockage : congelés, le pouvoir inhibiteur de ces PRM ne montre pas d'évolution significative au cours des deux premiers mois de conservation.

The formation of green trihydroxy benzacridine (TBA) derivatives when chlorogenic acid (CGA) quinones and amino acids react can be visually unappealing in some applications where CGA containing ingredients are used. Cysteine was studied as an amino acid anti-greening strategy, because cysteine-CGA conjugates are colorless. Buffered CGA: lysine: cysteine solutions at pH 8.0 and 9.0 were prepared and incubated for a maximum of 48 h at ambient temperature. Color intensity was periodically monitored using a UV-Vis spectrophotometer. Quantification and identification of conjugate formation were conducted by HPLC and LC-MS, while Antioxidant capacity was assessed by Trolox Equivalent Antioxidant Capacity and Folin-Ciocalteu reagent reducing capacity assays. More intense greening was detected at higher pH. Lysyl amine- CGA conjugates were identified as the predominant precursor of green TBA. Concentration-dependent cysteine inhibition of CGA-lysine greening was primarily by redox diphenol regeneration when pH was below cysteinyl thiol pKa 8.3 while primarily by forming cysteinyl-CGA conjugates when pH was above 8.3. Visible greening was fully inhibited with a cysteine: lysine 1:1 molar ratio in pH 9 CGA: Lys: Cys solutions, indicating that cysteinyl thiol was a stronger nucleophile than ε-lysyl amine to react with CGA o-quinones. Mono- and di-cysteine-CGA conjugates contributed to antioxidant capacity. Cysteine concentration, pH and incubation time all significantly affected color intensities and antioxidant capacity (p

The polyphenol pathway and Maillard reaction (polycondensation of sugars and amino acids) are regarded as important pathways in natural humification. The significance of linking the Maillard reaction and polyphenol pathways into an integrated humification pathway has been addressed. However, the ability of mineral colloids commonly occurring in tropical and temperate environments to promote the Maillard reaction and integrated polyphenol-Maillard humification pathways remained to be uncovered. Furthermore, the effect of the nature and relative abundance of biomolecules on humification and associated reaction products remained to be studied.<p>The results of this study show that the structure of polyphenols and the relative molar ratio of polyphenol, glucose and glycine, significantly affected humification processes and the associated carbonate formation in the integrated polyphenol-Maillard reaction catalyzed by birnessite. Increasing the molar ratio of ortho-polyphenols (catechol and pyrogallol) to Maillard reagents in the polyphenol-Maillard pathway catalyzed by birnessite enhanced humification while suppressing the formation of rhodochrosite (MnCO3). The opposite trend of MnCO3 formation was observed in the meta-polyphenol (resorcinol)-Maillard reaction system. Increasing the amount of glucose in the integrated catechol-Maillard system under the catalysis of birnessite promoted the formation of Maillard reaction-type humic acid in the supernatant and MnCO3 in the solid phase.<p>The catalytic abilities of commonly occurring mineral colloids from temperate and tropical regions greatly differed in influencing humification processes and products in the Maillard reaction and integrated polyphenol-Maillard pathways. Compared with layer silicate colloids, the poorly ordered Fe and Mn oxides were by far the strongest catalysts of humification reactions in the Maillard and catechol-Maillard pathways. This accounted for the significant difference in reactivity between the sesquioxide-rich Oxisol clay from the high rainfall region of South Africa and the Mollisol clay from the Canadian Prairies. Furthermore, the nature of the mineral colloids also affected the extent of organic C accumulation in the solid phase upon humification, and related mineral surface alteration. The metal oxide- and Oxisol clay-catalyzed Maillard and catechol-Maillard reaction systems had the highest accumulation of organic C in the solid phase, indicating their significance in contributing to C sequestration in the environment.<p>The findings obtained in this study are of fundamental significance in understanding the influence of the atomic bonding, structural configuration and related surface properties of mineral colloids, and the nature and abundance of biomolecules on the abiotic humification pathways and related reaction products in natural environments.

The polyphenol pathway and Maillard reaction (polycondensation of sugars and amino acids) are regarded as important pathways in natural humification. The significance of linking the Maillard reaction and polyphenol pathways into an integrated humification pathway has been addressed. However, the ability of mineral colloids commonly occurring in tropical and temperate environments to promote the Maillard reaction and integrated polyphenol-Maillard humification pathways remained to be uncovered. Furthermore, the effect of the nature and relative abundance of biomolecules on humification and associated reaction products remained to be studied.<p>The results of this study show that the structure of polyphenols and the relative molar ratio of polyphenol, glucose and glycine, significantly affected humification processes and the associated carbonate formation in the integrated polyphenol-Maillard reaction catalyzed by birnessite. Increasing the molar ratio of ortho-polyphenols (catechol and pyrogallol) to Maillard reagents in the polyphenol-Maillard pathway catalyzed by birnessite enhanced humification while suppressing the formation of rhodochrosite (MnCO3). The opposite trend of MnCO3 formation was observed in the meta-polyphenol (resorcinol)-Maillard reaction system. Increasing the amount of glucose in the integrated catechol-Maillard system under the catalysis of birnessite promoted the formation of Maillard reaction-type humic acid in the supernatant and MnCO3 in the solid phase.<p>The catalytic abilities of commonly occurring mineral colloids from temperate and tropical regions greatly differed in influencing humification processes and products in the Maillard reaction and integrated polyphenol-Maillard pathways. Compared with layer silicate colloids, the poorly ordered Fe and Mn oxides were by far the strongest catalysts of humification reactions in the Maillard and catechol-Maillard pathways. This accounted for the significant difference in reactivity between the sesquioxide-rich Oxisol clay from the high rainfall region of South Africa and the Mollisol clay from the Canadian Prairies. Furthermore, the nature of the mineral colloids also affected the extent of organic C accumulation in the solid phase upon humification, and related mineral surface alteration. The metal oxide- and Oxisol clay-catalyzed Maillard and catechol-Maillard reaction systems had the highest accumulation of organic C in the solid phase, indicating their significance in contributing to C sequestration in the environment.<p>The findings obtained in this study are of fundamental significance in understanding the influence of the atomic bonding, structural configuration and related surface properties of mineral colloids, and the nature and abundance of biomolecules on the abiotic humification pathways and related reaction products in natural environments.

M.Tech.Chemical Engineering. / The distillery wastewaters released from industries that use molasses as a major source of carbon in their fermentation processes pose serious threats to the water quality in several regions around the globe. Melanoidin is an antioxidant that results from the Malliard reaction found in fermentation and distillation processes. This study explores the removal of melanoidin from aqueous solution using natural clinoptilolite modified using cationic surfactant hexadecyltrimethyl ammonium bromide. The absorbent media was characterized using analyatical techniques such as BET, FTIR, SEM-EDS and XRD analysis. Given the relatively low cost of natural zeolite, it is possible to apply the sorbent in polishing distillery wastewater after a biological process. Since both natural zeolites and distillery waste streams are used in agriculture, a prudent way to dispose the spent media is to use it as fertilizer in farming.

The extent of denaturation and glycation of lysozyme and BSA with the application of high hydrostatic pressure (HHP) at 400 MPa at 30°C from 8 to 48 hours and focused microwave irradiation at 50°C under varying microwave power and from 10 to 60 minutes was investigated in the presence and absence of D-glucose. The HHP treatment caused 10 to 20% denaturation of lysozyme whereas microwave irradiation caused 20 to 40% denaturation, with more destruction to the lysozyme in the presence of glucose compared to the control. The extent of glycation was also higher with the high pressure samples, causing 60% glycation upon 8 hours of high pressure exposure, but decreasing to around 40% thereafter. Microwave irradiation brought about 40% glycation to the lysozyme samples upon 20 min of irradiation. BSA, on the other hand, was more susceptible to damage by high energy exposures. BSA samples were denatured to a greater extent compared to lysozyme, up to 80% upon the prolonged exposures, but in all treatments, glucose seemed to act as a protectant contrary to the case of lysozyme. The extent of glycation detected was also minimal, ranging from 8 to 20%. / The feasibility of analyzing glycated proteins using pyrolysis-GC/MS was also investigated. Taking advantage of the formation of a diagnostic marker---2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one---upon pyrolysis of glycated proteins, the intensity of this peak was used to correlate the extent of glycation. The intensity of this peak in the pyrograms of glycated lysozymes was found to increase linearly with increasing incubation times and subsequently with the sugar loads of the glycated lysozyme. In addition, using the pyrograms as unique fingerprints, the extent of structural changes between modified and unmodified proteins were also assessed.

Thesis (M.Sc.) -- Memorial University of Newfoundland, 1987. / Typescript. Bibliography: leaves 56-64. Also available online.