- 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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- The effects of thermal treatment of ZnO–ZnCr2O4 catalyst on the particle size and product selectivity in dehydrocyclization of crude glycerol and ethylenediamine
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The ZnO–ZnCr2O4 (Zn–Cr–O) sample obtained by decomposition of Zn-Cr hydrotalcite precursor was subjected to the thermal treatment at different temperatures and the physico-chemical properties of the Zn–Cr–O system were compared with
- Sarkari, Reema,Krishna, Vankudoth,Sudhakar, Medak,Rao, Tumula Venkateshwar,Padmasri, Aytam Hari,Srinivas, Darbha,Venugopal, Akula
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p. 602 - 609
(2016/10/18)
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- 1H-pyrrole-2,4-dicarbonyl-derivatives and their use as flavoring agents
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The present invention primarily relates to 1H-pyrrole-2,4-dicarbonyl-derivatives of Formula (I) wherein R1, R2, R3, Z. Z' and J are as defined in the description, to mixtures thereof and to the use thereof as flavoring agents. The compounds in accordance with the present invention are suitable for producing, imparting, or intensifying an umami flavor. The invention further relates to flavoring mixtures, compositions for oral consumption as well as ready-to-eat, ready-to-use and semifinished products, comprising an effective amount of the compound of Formula (I) or of a mixture of compounds of Formula (I) and to specific methods for producing, imparting, modifying and/or intensifying specific flavor impressions.
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- Imidazo[1,2-a]pyridine-ylmethyl-derivatives and their use as flavoring agents
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The present invention primarily relates to imidazo[1,2-a]pyridine-ylmethyl-derivatives of Formula (I) wherein R1, R2, X, W e J are as defined in the description, to mixtures thereof and to the use thereof as flavoring agents. The compounds in accordance with the present invention are suitable for producing, imparting, or intensifying an umami flavor. The invention further relates to flavoring mixtures, compositions for oral consumption as well as ready-to-eat, ready-to-use and semifinished products, comprising an effective amount of the compound of Formula (I) and to specific methods for producing, imparting, modifying and/or intensifying specific flavor impressions.
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- Influence of Free Amino Acids, Oligopeptides, and Polypeptides on the Formation of Pyrazines in Maillard Model Systems
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Pyrazines are specific Maillard reaction compounds known to contribute to the unique aroma of many products. Most studies concerning the generation of pyrazines in the Maillard reaction have focused on amino acids, while little information is available on the impact of peptides and proteins. The present study investigated the generation of pyrazines in model systems containing whey protein, hydrolyzed whey protein, amino acids, and glucose. The impact of thermal conditions, ratio of reagents, and water activity (aw) on pyrazine formation was measured by headspace solid-phase microextraction with gas chromatography/mass spectrometry (HS-SPME-GC/MS. The presence of oligopeptides from hydrolyzed whey protein contributed significantly to an increased amount of pyrazines, while in contrast free amino acids generated during protein hydrolysis contributed to a lesser extent. The generation of pyrazines was enhanced at low aw (0.33) and high temperatures (>120 °C). This study showed that the role of peptides in the generation of pyrazines in Maillard reaction systems has been dramatically underestimated.
- Scalone, Gustavo Luis Leonardo,Cucu, Tatiana,De Kimpe, Norbert,De Meulenaer, Bruno
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p. 5364 - 5372
(2015/06/25)
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- γ-Maghemite-silica nanocomposite: A green catalyst for diverse aromatic N-heterocycles
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γ-Maghemite-silica nanocomposite has been applied as a green catalyst to synthesize variety of aromatic N-heterocycles under solvent free conditions. Characterization was done by modern analytical tools (UV, IR, AAS, DSC, EDXRF, powdered XRD, EPR, Mo?ssbauer and TEM). Mild reaction conditions and recyclability have made the present protocol both environmentally and economically viable.
- Ghosh, Pranab,Mandal, Amitava,Subba, Raju
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p. 146 - 152
(2013/09/02)
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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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- Vapor phase synthesis of methylpyrazine using aqueous glycerol and ethylenediamine over ZnCr2O4 catalyst: Elucidation of reaction mechanism
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A novel method has been developed for the synthesis of methylpyrazine (MP) by using aqueous glycerol and ethylenediamine (EDA) over Zn-Cr catalyst derived from hydrotalcite precursors. The X-ray diffraction analysis of the oven-dried Zn-Cr samples synthesized at various pH ranging from 7 to 11 showed hydrotalcite phase whereas the calcined catalysts displayed ZnO and ZnCr2O 4 phases. The cyclisation activity of Zn-Cr catalyst prepared at pH ～ 9 demonstrated 99.4% conversion of EDA and 94% of glycerol with ～ 72% selectivity to MP at a reaction temperature of 400 °C. This process demonstrates direct utilization of bio-glycerol for the synthesis of MP.
- Sarkari, Reema,Anjaneyulu, Chatla,Krishna, Vankudoth,Kishore, Ramineni,Sudhakar, Medak,Venugopal, Akula
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experimental part
p. 1067 - 1070
(2012/01/15)
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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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- EFFECT OF TIME AND TEMPERATURE ON THE PREPARATION OF PYRAZINES IN MODEL REACTIONS OF THE SYNTHESIS OF AROMA-FORMING SUBSTANCES
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The qualitative and quantitative compositions of pyrazines that form in model glucose-ammonia and glucose-ammonia-leucine reactions in a glycerol medium were studied.Reaction conditions were found that ensure the synthesis of 23 alkylpyrazines in total concentration ca. 6 g/kg.The obtained mixture of pyrazines is promising for use in the development of food aroma-forming substances.Keywords: pyrazines, Maillard reaction, capillary gas chromatography.
- Misharina, T. A.,Golovnya, R. V.,Yakovleva, V. N.
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p. 1258 - 1263
(2007/10/02)
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- Ueber die Synthese von 2,3-Dialkylpyrazinen
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2,3-Dialkylquinoxalines (4), which are available from the reaction of benzofuroxan (1) with ketones and subsequent reduction of the 2,3-dialkylquinoxaline N,N'-dioxides (3), are converted to 2,3-dialkylpyrazines (6) by oxidation-decarboxylation steps.
- Heyns, Kurt,Behse, Ernst,Francke, Wittko
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p. 240 - 245
(2007/10/02)
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- Studies on the Thermolysis of 2-(2-Hydroxy-2-arylethyl)pyrazines. An Example of a Retro-Ene-Type Reaction
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Several substituted 2-(2-hydroxy-2-arylethyl)pyrazines (1-10) have been prepared and their thermolysis in diglyme and DMF studied.Each of these substrates decomposes to give the parent methylpyrazine and the corresponding aryl aldehyde.Kinetic, isotope effect, and solvent effect studies suggest a mechanism involving a nonpolar concerted six-membered-ring transition state.The degree of proton transfer in the transition state is discussed in detail.Methyl substituents on the pyrazine ring were found to strongly affect the reaction rate.This phenomenon is analyzed interms of the steric and electronic effects induced by the methyl substituents.
- Houminer, Yoram
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p. 999 - 1003
(2007/10/02)
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