- Comparison of pyrazines formation in methionine/glucose and corresponding Amadori rearrangement product model
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The generation of pyrazines in a binary methionine/glucose (Met/Glc) mixture and corresponding methionine/glucose-derived Amadori rearrangement product (MG-ARP) was studied. Quantitative analyses of pyrazines and methional revealed that MG-ARP generated more methional compared to Met/Glc, whereas lower content and fewer species of pyrazines were observed in the MG-ARP model. Comparing the availability of α-dicarbonyl compounds generated from the Met/Glc model, methylglyoxal (MGO) was a considerably effective α-dicarbonyl compound for the formation of pyrazines during MG-ARP degradation, but glyoxal (GO) produced from MG-ARP did not effectively participate in the corresponding formation of pyrazines due to the asynchrony on the formation of GO and recovered Met. Diacetyl (DA) content was not high enough to form corresponding pyrazines in the MG-ARP model. The insufficient interaction of precursors and rapid drops in pH limited the formation of pyrazines during MG-ARP degradation. Increasing reaction temperature could reduce the negative inhibitory effect by promoting the content of precursors.
- Cui, Heping,Deng, Shibin,Hayat, Khizar,Ho, Chi-Tang,Zhai, Yun,Zhang, Qiang,Zhang, Xiaoming
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- Characteristic flavor formation of thermally processed N-(1-deoxy-α-D-ribulos-1-yl)-glycine: Decisive role of additional amino acids and promotional effect of glyoxal
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The role of amino acids and α-dicarbonyls in the flavor formation of Amadori rearrangement product (ARP) during thermal processing was investigated. Comparisons of the volatile compounds and their concentrations when N-(1-deoxy-α-D-ribulos-1-yl)-glycine r
- Zhan, Huan,Cui, Heping,Yu, Junhe,Hayat, Khizar,Wu, Xian,Zhang, Xiaoming,Ho, Chi-Tang
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- Alkylations and hydroxymethylations of pyrazines via green minisci-type reactions
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A new general methodology utilizing Minisci-type chemistry has been developed that cleanly and efficiently prepares alkyl- and (hydroxymethyl) pyrazines. The new methods eliminate toxic catalysts and halogenated solvents, providing a greatly improved route to these natural products which are prevalent in many natural systems as bacterial volatiles, plant volatiles, and insect pheromones.
- Bohman, Bjorn,Berntsson, Benjamin,Dixon, Ruby C. M.,Stewart, Craig D.,Barrow, Russell A.
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supporting information
p. 2787 - 2789
(2014/06/23)
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- 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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- Pyrazine biosynthesis in corynebacterium glutamicum
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The volatile compounds released by Corynebacterium glutamicum were collected by use of the CLSA technique (closed-loop stripping apparatus) and analysed by GC-MS. The headspace extracts contained several acyloins and pyrazines that were identified by their synthesis or comparison to commercial standards. Feeding experiments with [2H7]acetoin resulted in the incorporation of labelling into trimethylpyrazine and tetramethylpyrazine. Several deletion mutants targeting genes of the primary metabolism, were constructed to elucidate the biosynthetic pathway to pyrazines in detail. A deletion mutant of the ketol-acid reductoisomerase was not able to convert the acetoin precursor (S)2-acetolactate into the pathway intermediate (R)-2,3-dihydroxy-3-methylbutanoate to the branched amino acids. This mutant requires valine, leucine, and isoleucine for growth and produces significantly higher amounts and more different compounds of the acyloin and pyrazine classes. Gene deletion of the acetolactate synthase (AS) resulted in a mutant that is not able to convert pyruvate into (5)-2-acetolactate. This mutant also requires branched amino acids and produces only very small amounts of pyrazines likely from valine via the valine biosynthetic pathway operating in reverse order. A ΔASΔKR double mutant was constructed that does not produce any pyrazines at all. These results open up a detailed biosynthetic model for the formation of alkylated pyrazines via acyloins.
- Dickschat, Jeroen S.,Wickel, Susanne,Bolten, Christoph J.,Nawrath, Thorben,Schulz, Stefan,Wittmann, Christoph
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supporting information; experimental part
p. 2687 - 2695
(2010/08/07)
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- Preparation of pyrazines
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The present invention relates to a new process for the generation of pyrazines consisting in the bioconversion of hydroxyketones with 1,2-diaminopropane. New tetrahydropyrazine derivatives as well as new dihydropyrazine derivatives with high flavour and low threshold properties are disclosed. Such pyrazines compounds exhibiting roasted and earthy aroma profiles may be used in the food and bevererage industry, especially chocolate, confectionery and coffee.
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- Regioselective Synthesis of Alkylpyrazines
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A new, regioselective synthesis of alkylpyrazines begins with condensation of α-oximido carbonyl compounds with allylamines.The resulting imines are isomerized in the presence of potassium tert-butoxide to the corresponding 1-hydroxy-1,4-diazahexatrienes.Thermal electrocyclization-aromatization to pyrazines is best performed after O-acylation of the oximes with methyl chloroformate.
- Buechi, George,Galindo, Jose
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p. 2605 - 2606
(2007/10/02)
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