Mechanism of Pyrazine Formation Intervened by Oxidized Methionines during Thermal Degradation of the Methionine–Glucose Amadori Compound

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The involvement of exogenous threonine during the degradation of L-threonine-D-xylose Amadori rearrangement product (Thr-ARP) was found to promote the formation of pyrazines. A model including Thr-ARP and 15 N-labeled L-threonine was applied to reveal the role of free threonine in Thr-ARP conversion to pyrazines. Quantitative analyses of pyrazines in the model of Thr-ARP/ 15 N-labeled threonine showed a precedence of the endogenous threonine (formed by the degradation of Thr-ARP) over the exogenous threonine in pyrazines formation, and the ratio of 15 N to 14 N content in pyrazines increased significantly over time. According to the observed occurrence of the Heyns rearrangement products (HRP) derived from 15 N-threonine, as well as the sharp decrease of 15 N-threonine content and a rapid increase of 14 N endogenous threonine at the initial stage of heat treatment, it was proposed that aldimine condensation between exogenous threonine and Thr-ARP followed by the hydrolysis led to the endogenous threonine and the generation of HRP. Then, the HRP underwent dehydration followed by hydrolysis to form exogenous threonine and deoxyxyosones, and the dehydration and hydrolysis of deoxyxyosones to form organic acids was inhibited, but the retroaldolization of deoxyxyosones was promoted, facilitating the generation of reactive α-dicarbonyl compounds. In this way, exogenous threonine accelerated the release of endogenous threonine and α-dicarbonyl compounds and the pH decline was slowed down, which was favorable for the formation of pyrazines.

Section: Methodsmentioning

confidence: 99%

Section: ■ Materials and Methodsmentioning

confidence: 99%

Exogenous Threonine-Induced Conversion of Threonine-Xylose Amadori Compound to Heyns Compound for Efficiently Promoting the Formation of Pyrazines

Chen

Cui

Zhou

et al. 2023

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“…The accumulation of Amadori compounds and α-dicarbonyl compounds in F3 might reach an equilibrium; thus, α-dicarbonyl compounds, ARPs, and release peptides existed simultaneously in MRIs. As a result, the α-dicarbonyl compounds were continuously generated during the subsequent thermal reaction, leading to the continuous production of pyrazines. , …”

Section: Resultsmentioning

confidence: 99%

“…The simultaneous presence of amino acids, regenerated peptides, and sufficient αdicarbonyl compounds is an important prerequisite for the generation of pyrazines. 31 Deng et al 34 proposed that the formation of 2,5-dimethylpyrazine, 2,6-dimethylpyrazine, and methylpyrazine was only detected in the presence of both ARP and amino acids or peptides; additionally, the presence of amino acids was a necessary condition for unsubstituted pyrazine generation. The accumulation of Amadori compounds and α-dicarbonyl compounds in F3 might reach an equilibrium; thus, α-dicarbonyl compounds, ARPs, and release peptides existed simultaneously in MRIs.…”

Section: Sensitive Characterization and Effective Prediction Of The O...mentioning

confidence: 99%

Maillard Reaction Process and Characteristic Volatile Compounds Formed During Secondary Thermal Degradation Monitored via the Change of Fluorescent Compounds in the Reaction of Xylose–Corn Protein Hydrolysate

Li,

Yao,

Xia

et al. 2023

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Until now, no effective method has been found to monitor the Maillard reaction process for complex protein hydrolysates. Dynamic changes in the concentration of α-dicarbonyl compounds, fluorescence intensity, and browning degree were investigated during the Maillard reaction of corn protein hydrolysates. When the fluorescence intensity reached the peak, deoxyosones would continue to be increased by ARP's degradation. However, the reaction node with the highest fluorescence intensity coincided with the turning point of the browning reaction, and the subsequent browning rate remarkably increased. Therefore, the change in fluorescence intensity could be used to monitor the degradation of ARP and the formation of browning melanoidin at different stages of the Maillard reaction of complex systems, thus effectively indicating the process of the Maillard reaction. When Maillard reaction intermediates (MRIs) with maximum fluorescent compounds were heated, the most abundant pyrazines were subsequently achieved. However, furan compounds would be progressively increased during the thermal process of MRIs with continuously enhanced browning.

“…The quantitative analysis of GSH, RG-ARP, and GSH secondary byproducts was performed through an ACQUITY UPLC−TQD system (Waters) with the pure GSH, RG-ARP, PGA, Cys−Gly, GSSG, RCG-ARP, and RGG-ARP as external standards. 19 Multiple reaction monitoring (MRM) and single-scan mode were used to identify the key compounds in the ESI + mode, and the voltage and ion parameters are shown in Table S1. The quantitation was carried out by determining optimal ion abundance.…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

Efficient Formation of N-(1-Deoxy-d-ribulos-1-yl)-Glutathione via Limited Oxidation and Degradation of Glutathione during the Atmospheric–Vacuum Thermal Reaction

Feng,

Cui,

Chen

et al. 2023

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The efficient preparation of the ribose-glutathione (Rib-GSH) Amadori rearrangement product (RG-ARP) as a potent precursor of meaty flavor was studied through the atmospheric−vacuum thermal reaction. Liquid chromatography−mass spectrometry (LC−MS) analysis revealed that the oxidation and degradation of GSH occurred during the preparation of RG-ARP via the atmospheric thermal reaction, especially at a low molar ratio of Rib to GSH and high reaction temperature. The RG-ARP and the ARPs derived from the products of GSH oxidation and degradation with the participation of Rib were identified by MS/MS as N-(1-deoxy-D-ribulos-1-yl)-glutathione, N-(1-deoxy-D-ribulos-1-yl)-cysteinylglycine, and N-(1-deoxy-D-ribulos-1-yl)-glutathionedisulfide. The selective formation of RG-ARP was disrupted due to the multiple consumption pathways of GSH and Rib. The removal of water and the reduction of oxygen content during vacuum dehydration exhibited an obvious inhibitory effect on the oxidation of cysteinyl and the cleavage of glutamyl, limiting the oxidation and degradation of GSH. Meanwhile, the rapid evaporation of water promoted the molecular collision between the reactants, which allowed the glycation reaction of GSH to be advanced and fragmentation of RG-ARP to be inhibited at a mild dehydration temperature. Accordingly, the atmospheric−vacuum thermal reaction was proposed to limit the generation of secondary byproducts and enhance the yield of RG-ARP, enabling the RG-ARP yield to reach 49.23% at 80 °C and a molar ratio of 2:1 (Rib/GSH) for 20 min.