Abstract In this study the thermal degradation of ovalbumin (OVA) under nitrogen atmosphere was investigated. For this scope, a multi instrumental approach based on thermogravimetry (TG), thermogravimetry coupled with infrared spectroscopy (TG/FTIR) and pyrolysis coupled with mass spectrometric detection, i.e. flash pyrolysis-coupled with gas chromatography-mass spectrometry (Py/GC/MS), evolved gas analysis coupled with mass spectrometry (EGA/MS) and double shot pyrolysis-coupled with gas chromatography-mass spectrometry (DSP/GC/MS), was used. The pyrolysis of a protein involves a combination of several complex mechanisms resulting in a very high number of products. The study highlighted that pyrolysis of OVA produces low-molecular weight gasses, such as CO2, H2O, HCNO, NH3 and CO, as main compounds. In addition, a series of organic compounds containing heteroatoms and unsaturations were also identified, whose formation occurred at different temperatures over the pyrolytic process. Among these, cyclic pyrolysis products were identified: dialkyl substituted 2,5-diketopiperazines (DKPs) and, for the first time, unsaturated-DKPs (un-DKPs), 3,5-alkyl-3,4-dihydro-2H-pyrrole-2,4-diones (ADPDs) and 3-alkenyl-5-alkyl-pyrrolidine-2,4-diones (AAPDs). These compounds are formed below 350°, and are produced by cyclisation reactions of two neighbouring amino acids. Pyroglutamic acid was also found among the main pyrolysis products of OVA, obtained as pyrolytic product of Glu, which is the most abundant amino acid in OVA. Aromatic compounds, such as pyridine, pyrrole, toluene, alkyl-benzenes and alkyl-pyrroles, phenol and alkyl-phenols, benzeneacetonitrile, benzenepropanenitrile, indole and alkyl-indoles, were detected, produced over a wide range of temperatures. This study highlighted for the first time that aromatic compounds produced below 320 °C are associated to the pyrolysis of specific amino acid side chains, while at higher temperatures, they are the pyrolysis products of the residual material remaining after condensation reactions, pyrolytic scissions and cyclization reactions.

中文翻译：

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卵清蛋白的分析热解

摘要 本研究研究了卵清蛋白（OVA）在氮气氛下的热降解。对于此范围，基于热重法 (TG)、热重法与红外光谱 (TG/FTIR) 和热解与质谱检测耦合的多仪器方法，即快速热解与气相色谱-质谱联用 (Py/GC/MS) )，使用了逸出气体分析与质谱联用 (EGA/MS) 和双喷射热解与气相色谱-质谱联用 (DSP/GC/MS)。蛋白质的热解涉及多种复杂机制的组合，从而产生大量产品。该研究强调，OVA 的热解会产生作为主要化合物的低分子量气体，例如 CO2、H2O、HCNO、NH3 和 CO。此外，还确定了一系列含有杂原子和不饱和度的有机化合物，它们的形成发生在热解过程的不同温度下。其中，确定了环状热解产物：二烷基取代的 2,5-二酮哌嗪 (DKPs) 和首次不饱和 DKPs (un-DKPs)、3,5-烷基-3,4-二氢-2H-吡咯-2,4-二酮 (ADPD) 和 3-烯基-5-烷基-吡咯烷-2,4-二酮 (AAPD)。这些化合物在 350°以下形成，由两个相邻氨基酸的环化反应产生。在 OVA 的主要热解产物中也发现了焦谷氨酸，作为 OVA 中最丰富的氨基酸 Glu 的热解产物获得。芳香族化合物，例如吡啶、吡咯、甲苯、烷基苯和烷基吡咯、苯酚和烷基苯酚、苯乙腈、检测到苯丙腈、吲哚和烷基吲哚，它们在很宽的温度范围内产生。该研究首次强调，在 320 °C 以下产生的芳香族化合物与特定氨基酸侧链的热解有关，而在较高温度下，它们是缩合反应、热解断裂和环化后剩余物质的热解产物反应。