Institut für Lebensmitteltechnologie und Lebensmittelchemie, Fachgruppe Lebensmittelchemie und Analytik, Technische Universität Berlin, Gustav-Meyer-Allee 25, 13355 Berlin, Germany.
Institut für Chemie, Max-Volmer-Labor für Biophysikalische Chemie, Technische Universität Berlin, Straße des 17. Juni, 135, 10623 Berlin, Germany.
Food Chem. 2018 Apr 15;245:761-767. doi: 10.1016/j.foodchem.2017.11.115. Epub 2017 Dec 8.
The aim of this study was to identify specific chemical bonds and characteristic structures in melanoidins formed from d-glucose and l-alanine between 130 and 200 °C. The results might be used to control the type and amount of melanoidin produced during food processing. For this purpose, complementary techniques, such as FTIR, NMR, EPR, and MALDI-ToF, were employed. At 160 °C color, solubility and UV/Vis absorption change characteristically and consequently, structural transformations could be observed in FTIR and NMR spectra. For example, sharp signals of N-H, C-N, and C-H oscillations in the l-alanine spectrum are prone to inhomogeneous broadening in melanoidins prepared above 150 °C. These changes are caused due to formation of heterogeneous macromolecular structures and occur during condensation reactions that lead to an increasing loss of water from the melanoidins with increasing temperatures. Additionally, MALDI-ToF-MS indicates the polymerization of glyoxal/glyoxylic acid and EPR shows the formation of radical structures.
本研究旨在鉴定 130-200°C 下由 d-葡萄糖和 l-丙氨酸形成的类黑精中特定的化学键和特征结构。这些结果可用于控制食品加工过程中类黑精的种类和数量。为此，采用了傅里叶变换红外光谱（FTIR）、核磁共振（NMR）、电子顺磁共振（EPR）和基质辅助激光解吸电离飞行时间质谱（MALDI-ToF）等互补技术。在 160°C 时，颜色、溶解度和紫外/可见光吸收特性发生变化，因此可以在 FTIR 和 NMR 光谱中观察到结构转变。例如，l-丙氨酸谱中 N-H、C-N 和 C-H 振动的尖锐信号在 150°C 以上制备的类黑精中容易发生不均匀展宽。这些变化是由于形成不均匀的大分子结构以及在导致类黑精随着温度升高不断失去水分的缩合反应中引起的。此外，MALDI-ToF-MS 表明乙二醛/乙醛酸的聚合，EPR 表明自由基结构的形成。
