Hydroxycinnamic Acid – Maillard Reactions in Simple Aqueous Model Systems

Author(s):  
Marlene R. Moskowitz ◽  
Devin G. Peterson
2019 ◽  
Author(s):  
Isaac Omari ◽  
Hannah Charnock ◽  
Alexa Fugina ◽  
Euan Thomson ◽  
J Scott McIndoe

Magnesium impacts key processes in brewing including yeast metabolism and mash pH but is typically overshadowed in brewing studies, owing to the established centrality of calcium. Using flame atomic absorption spectroscopy (FAAS), we have identified a 33.7% average increase in magnesium concentration in commercially available beers brewed with 100% barley malt versus those brewed with adjunct grains. Parallel analysis of brewing grains implicates rice in driving this discrepancy. Given the known catalytic properties of magnesium, we investigated its role in beer color development via Maillard chemistry using model systems and wort (unfermented beer). Kinetic data were obtained by ultraviolet-visible spectrometry and reaction species were identified by electrospray ionization mass spectrometry. Magnesium accelerated Maillard chemistry in all systems in a dose-dependent manner. It is proposed that magnesium inhibits water mobility and serves as a Lewis acid catalyst to facilitate Maillard reactions.


1985 ◽  
Vol 53 (2) ◽  
pp. 281-292 ◽  
Author(s):  
Henrik K. Nielsen ◽  
D. De Weck ◽  
P. A. Finot ◽  
R. Liardon ◽  
R. F. Hurrell

1. The stability of tryptophan was evaluated in several different food model systems using a chemical method (high pressure liquid chromatography after alkaline-hydrolysis) and rat assays. Losses of tryptophan were compared with the losses of lysine and methionine.2. Whey proteins stored in the presence of oxidizing lipids showed large losses of lysine and extensive methionine oxidation but only minor losses of tryptophan as measured chemically. The observed decrease in bioavailable tryptophan was explained by a lower protein digestibility.3. Casein treated with hydrogen peroxide to oxidize all methionine to methionine sulphoxide showed a 9% loss in bioavailable tryptophan.4. When casein was reacted with caffeic acid at pH 7 in the presence of monophenol monooxygenase (tyrosinase; EC 1.14.18.l), no chemical loss of tryptophan occurred, although fluorodinitrobenzene-reactive lysine fell by 23%. Tryptophan bioavailability fell IS%, partly due to an 8% reduction in protein digestibility.5. Alkali-treated casein (0.15 M-sodium hydroxide, 80°,4 h) did not support rat growth. Chemically-determined tryptophan, available tryptophan and true nitrogen digestibility fell 10, 46 and 23% respectively. Racemization of tryptophan was found to be 10% (D/(D+L)).6. In whole-milk powder, which had undergone ‘early’ or ‘advanced’ Maillard reactions, tryptophan, determined chemically or in rat assays, was virtually unchanged. Extensive lysine losses occurred.7. It was concluded that losses of tryptophan during food processing and storage are small and of only minor nutritional importance, especially when compared with much larger losses of lysine and the more extensive oxidation of methionine.


2009 ◽  
Vol 57 (21) ◽  
pp. 9932-9943 ◽  
Author(s):  
Deshou Jiang ◽  
Christopher Chiaro ◽  
Pranav Maddali ◽  
K. Sandeep Prabhu ◽  
Devin G. Peterson

2018 ◽  
Vol 67 (3) ◽  
pp. 875-886 ◽  
Author(s):  
Wei Zhang ◽  
Colin Ray ◽  
Mahesha M. Poojary ◽  
Therese Jansson ◽  
Karsten Olsen ◽  
...  

2019 ◽  
Author(s):  
Isaac Omari ◽  
Hannah Charnock ◽  
Alexa Fugina ◽  
Euan Thomson ◽  
J Scott McIndoe

Magnesium impacts key processes in brewing including yeast metabolism and mash pH but is typically overshadowed in brewing studies, owing to the established centrality of calcium. Using flame atomic absorption spectroscopy (FAAS), we have identified a 33.7% average increase in magnesium concentration in commercially available beers brewed with 100% barley malt versus those brewed with adjunct grains. Parallel analysis of brewing grains implicates rice in driving this discrepancy. Given the known catalytic properties of magnesium, we investigated its role in beer color development via Maillard chemistry using model systems and wort (unfermented beer). Kinetic data were obtained by ultraviolet-visible spectrometry and reaction species were identified by electrospray ionization mass spectrometry. Magnesium accelerated Maillard chemistry in all systems in a dose-dependent manner. It is proposed that magnesium inhibits water mobility and serves as a Lewis acid catalyst to facilitate Maillard reactions.


Author(s):  
K. Brasch ◽  
J. Williams ◽  
D. Gallo ◽  
T. Lee ◽  
R. L. Ochs

Though first described in 1903 by Ramon-y-Cajal as silver-staining “accessory bodies” to nucleoli, nuclear bodies were subsequently rediscovered by electron microscopy about 30 years ago. Nuclear bodies are ubiquitous, but seem most abundant in hyperactive and malignant cells. The best studied type of nuclear body is the coiled body (CB), so termed due to characteristic morphology and content of a unique protein, p80-coilin (Fig.1). While no specific functions have as yet been assigned to CBs, they contain spliceosome snRNAs and proteins, and also the nucleolar protein fibrillarin. In addition, there is mounting evidence that CBs arise from or are generated near the nucleolus and then migrate into the nucleoplasm. This suggests that as yet undefined links may exist, between nucleolar pre-rRNA processing events and the spliceosome-associated Sm proteins in CBs.We are examining CB and nucleolar changes in three diverse model systems: (1) estrogen stimulated chick liver, (2) normal and neoplastic cells, and (3) polyploid mouse liver.


Author(s):  
Yih-Tai Chen ◽  
Ursula Euteneuer ◽  
Ken B. Johnson ◽  
Michael P. Koonce ◽  
Manfred Schliwa

The application of video techniques to light microscopy and the development of motility assays in reactivated or reconstituted model systems rapidly advanced our understanding of the mechanism of organelle transport and microtubule dynamics in living cells. Two microtubule-based motors have been identified that are good candidates for motors that drive organelle transport: kinesin, a plus end-directed motor, and cytoplasmic dynein, which is minus end-directed. However, the evidence that they do in fact function as organelle motors is still indirect.We are studying microtubule-dependent transport and dynamics in the giant amoeba, Reticulomyxa. This cell extends filamentous strands backed by an extensive array of microtubules along which organelles move bidirectionally at up to 20 μm/sec (Fig. 1). Following removal of the plasma membrane with a mild detergent, organelle transport can be reactivated by the addition of ATP (1). The physiological, pharmacological and biochemical characteristics show the motor to be a cytoplasmic form of dynein (2).


Author(s):  
Ian M. Anderson ◽  
Arnulf Muan ◽  
C. Barry Carter

Oxide mixtures which feature a coexistence of phases with the wüstite and spinel structures are considered model systems for the study of solid-state reaction kinetics, phase boundaries, and thin-film growth, and such systems are especially suited to TEM studies. (In this paper, the terms “wüstite” and “spinel” will refer to phases of those structure types.) The study of wüstite-spinel coexistence has been limited mostly to systems near their equilibrium condition, where the assumptions of local thermodynamic equilibrium are valid. The cation-excess spinels of the type Ni2(1+x)Ti1-xO4, which reportedly exist only above 1375°C4, provide an excellent system for the study of wüstite-spinel coexistence under highly nonequilibrium conditions. The nature of these compounds has been debated in the literature. X-ray and neutron powder diffraction patterns have been used to advocate the existence of a single-phase, non- stoichiometric spinel. TEM studies of the microstructure have been used to suggest equilibrium coexistence of a stoichiometric spinel, Ni2TiO4, and a wüstite phase; this latter study has shown a coexistence of wüstite and spinel phases in specimens thought to have been composed of a single, non- stoichiometric spinel phase. The microstructure and nature of this phase coexistence is the focus of this study. Specimens were prepared by ball-milling a mixture of NiO and TiO2 powders with 10 wt.% TiO2. The mixture was fired in air at 1483°C for 5 days, and then quenched to room temperature. The aggregate thus produced was highly porous, and needed to be infiltrated prior to TEM sample preparation, which was performed using the standard techniques of lapping, dimpling, and ion milling.


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