- Impact of the N-terminal amino acid on the formation of pyrazines from peptides in maillard model systems
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Only a minor part of Maillard reaction studies in the literature focused on the reaction between carbohydrates and peptides. Therefore, in continuation of a previous study in which the influence of the peptide C-terminal amino acid was investigated, this study focused on the influence of the peptide N-terminal amino acid on the production of pyrazines in model reactions of glucose, methylglyoxal, or glyoxal. Nine different dipeptides and three tripeptides were selected. It was shown that the structure of the N-terminal amino acid is determinative for the overall pyrazine production. Especially, the production of 2,5(6)-dimethylpyrazine and trimethylpyrazine was low in the case of proline, valine, or leucine at the N-terminus, whereas it was very high for glycine, alanine, or serine. In contrast to the alkyl-substituted pyrazines, unsubstituted pyrazine was always produced more in the case of experiments with free amino acids. It is clear that different mechanisms must be responsible for this observation. This study clearly illustrates the capability of peptides to produce flavor compounds such as pyrazines.
- Van Lancker, Fien,Adams, An,De Kimpe, Norbert
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scheme or table
p. 4697 - 4708
(2012/08/27)
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- Formation of pyrazines in maillard model systems of lysine-containing dipeptides
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Whereas most studies concerning the Maillard reaction have focused on free amino acids, little information is available on the impact of peptides and proteins on this important reaction in food chemistry. Therefore, the formation of flavor compounds from the model reactions of glucose, methylglyoxal, or glyoxal with eight dipeptides with lysine at the N-terminus was studied in comparison with the corresponding free amino acids by means of stir bar sorptive extraction (SBSE) followed by GC-MS analysis. The reaction mixtures of the dipeptides containing glucose, methylglyoxal, and glyoxal produced 27, 18, and 2 different pyrazines, respectively. Generally, the pyrazines were produced more in the case of dipeptides as compared to free amino acids. For reactions with glucose and methylglyoxal, this difference was mainly caused by the large amounts of 2,5(6)-dimethylpyrazine and trimethylpyrazine produced from the reactions with dipeptides. For reactions with glyoxal, the difference in pyrazine production was rather small and mostly unsubstituted pyrazine was formed. A reaction mechanism for pyrazine formation from dipeptides was proposed and evaluated. This study clearly illustrates the capability of peptides to produce flavor compounds that can differ from those obtained from the corresponding reactions with free amino acids.
- Van Lancker, Fien,Adams,De Kimpe, Norbert
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scheme or table
p. 2470 - 2478
(2010/09/04)
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- The effect of pH on the formation of aroma compounds produced by heating a model system containing l-ascorbic acid with l-threonine/l-serine
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The identification of aroma compounds, formed from the reactions of l-ascorbic acid with l-threonine/l-serine at five different pH values (5.00, 6.00, 7.00, 8.00, or 9.55) and 143 ± 2 °C for 2 h, was performed using a SPME-GC-MS technique, and further use
- Yu, Ai-Nong,Zhang, Ai-Dong
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experimental part
p. 214 - 219
(2011/12/14)
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- Synthesis of pyridines and pyrazines using an intramolecular hydroamination-based reaction sequence
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A management issue! Various pyridines and pyrazines can be efficiently accessed from simple acyclic precursors using an intramolecular hydroamination/isomerization/aromatization sequence (see scheme). ρ-Toluenesulfonic acid (2 mol%) is used to catalyze this novel alkyne annulation, in which the oxime group allows for a subsequent redoxneutral aromatization step to occur.
- Rizk, Toni,Bilodeau, Eric J.-F.,Beauchemin, Andre M.
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supporting information; experimental part
p. 8325 - 8327
(2010/01/16)
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- Pyrazine formation from serine and threonine
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The formation of pyrazines from L-serine and L-threonine has been studied. L-Serine and L-threonine, either alone or combined, were heated at 120 °C as low temperature for 4 h or at 300 °C as high temperature for 7 min. The pyrazines formed from each reaction were identified by GC/MS, and the yields (to the amino acid used, as parts per million) were determined by GC/FID. It was found that pyrazine, methylpyrazine, ethylpyrazine, 2-ethyl-6- methylpyrazine, and 2,6-diethylpyrazine were formed from serine, whereas 2,5- dimethylpyrazine, 2,6-dimethylpyrazine, trimethylpyrazine, 2-ethyl-3,6- dimethylpyrazine, and 2-ethyl-3,5-dimethylpyrazine were formed from threonine. Mechanistically, it is proposed that the thermal degradation of serine or threonine is composed of various complex reactions. Among these reactions, decarbonylation followed by dehydration is the main pathway to generate the α-aminocarbonyl intermediates leading to the formation of the main product, such as pyrazine from serine or 2,5-dimethylpyrazine from threonine. Also, deamination after decarbonylation generates more reactive intermediates, α-hydroxycarbonyls. Furthermore, aldol condensation of these reactive intermediates provides α-dicarbonyls. Subsequently, these α- dicarbonyls react with the remaining serine or threonine by Strecker degradation to form additional α-aminocarbonyl intermediates, which then form additional pyrazines. In addition, decarboxylation and retroaldol reaction may also involve the generation of the intermediates.
- Shu, Chi-Kuen
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p. 4332 - 4335
(2007/10/03)
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- Mechanisms of Formation of Alkylpyrazines in the Maillard Reaction
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The formation of alkylpyrazines was investigated in the reaction of glucose and fructose with -alanine and glycine.The reaction systems were heated for 7 min at 180 deg C.GC-MS and GC-MS/MS data were used to determine the rate of incorporati
- Amrani-Hemaimi, Miriam,Cerny, Christoph,Fay, Laurent B.
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p. 2818 - 2822
(2007/10/03)
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