Abstract：
The formation pathway and mechanism of various pyrazines were investigated during the thermal treatment of the alanine-xylose Amadori compound (Ala-ARP) and exogenous alanine (Ala). 15N-labeled Ala was used to coheated with Ala-ARP to clarify the nitrogen sources and the respective contributions of exogenous Ala and the regenerated Ala released from Ala-ARP to different pyrazine formation. It was found that exogenous Ala exhibited a priority in capturing glyoxal (GO) to form pyrazine during the thermal degradation of ARP. Compared to the Ala-methylglyoxal (MGO) model, a lower activation energy was required for the Ala-GO reaction, where the reaction dynamics of Ala-GO followed a zero-order model. In addition to forming pyrazine, the interaction between existing exogenous Ala and GO would accelerate the thermal degradation of Ala-ARP and retro-aldolization reaction of deoxyxylosones (DXs) to α-dicarbonyls. During this process, the release of regenerated Ala and MGO was promoted. Accordingly, as GO was expended by exogenous Ala during the initial stage of ARP-Ala degradation, the condensation between regenerated Ala and MGO became intensified, leading to the generation of methylpyrazine and 2,5-dimethylpyrazine. As a result, in the thermally treated mixture of Ala-ARP and exogenous Ala, 55% of the formed pyrazine originated from exogenous Ala, while 63% of the formed methylpyrazine and 57% of the formed 2,5-dimethylpyrazine were derived from regenerated Ala (120 °C, 30 min).
摘要：
在丙氨酸-木糖Amadori化合物（Ala-ARP）和外源丙氨酸（Ala）的热处理过程中，研究了各种吡嗪的形成途径和机理。使用15N标记的Ala与Ala-ARP共加热，以阐明氮源以及外源Ala和从Ala-ARP释放的再生Ala对不同吡嗪形成的各自贡献。已发现，外源Ala在ARP的热降解过程中优先捕获乙二醛（GO）以形成吡嗪。与Ala-甲基乙二醛（MGO）模型相比，Ala-GO反应需要较低的活化能，其中Ala-GO的反应动力学遵循零阶模型。除了形成吡嗪，现有的外源Ala和GO之间的相互作用会加速Ala-ARP的热降解和脱氧木糖酮（DXs）向α-二羰基的反醛缩反应。在这个过程中,促进了再生Ala和MGO的释放。因此，由于GO在ARP-Ala降解的初始阶段被外源Ala消耗，再生的Ala和MGO之间的冷凝加剧，导致甲基吡嗪和2,5-二甲基吡嗪的产生。因此,在Ala-ARP和外源Ala的热处理混合物中，55%的吡嗪起源于外源Ala，而63％的形成的甲基吡嗪和57％的形成的2,5-二甲基吡嗪来自再生的Ala（120°C，30分钟）。
