Structure-related degradation of pectins and their impact on non-enzymatic browning and technological functionality

食品的加工和储存会导致生物多聚体成分的化学和生化变化。因此，它们的功能特性通过非酶褐变反应和氧化过程进行了修饰。与还原糖相反，糖醛酸作为迈拉反应的前体很少被研究。因此，应研究果胶降解的反应过程、中间体和反应产物及其在非酶褐变反应中的作用。在模型系统中，第一个结果显示，与还原糖相比，糖醛酸的颜色发展更快。然而，水解性和消除β的裂解并不能提供充分的解释。此外，热诱导果胶降解的中间产物，如饱和和4，5-不饱和寡聚半乳糖醛酸，还没有得到系统的表征。关于改性果胶的功能性质，还需要进一步的研究。本项目的目的是研究和阐明热诱导果胶降解的反应机理。更确切地说，应该阐明原料的结构和使用条件对中间体形成的影响，以及它们在非酶褐变(美拉德反应)形成颜色中的作用。因此，不同的模型体系将分别与半乳糖醛酸及其甲酯一起使用。纯化的部分甲酯化的饱和和不饱和的寡聚半乳糖醛酸应在进一步的模型中单独使用。此外，研究结果将有助于深入了解果胶降解的机理及其对降解产物的物理化学特性的影响。以前执行的差示扫描量热法显示了异常，并推测了降解机理。作为该项目的一部分，对化学调查和结构分析表征的比较可以证实我们假设的降解机制。最后，应研究降解对果胶功能特性的影响。因此，核磁共振光谱学鉴定的结构应该与物理化学性质的研究结果相比较。

Processing and storage of food lead to chemical and biochemical changes in the biopolymeric constituents. Consequently, their functional properties modified by non-enzymatic browning reactions and oxidative processes. In contrast to reducing sugars, uronic acids as precursors in the Maillardreaction have rarely been studied. Hence, reaction processes, intermediates and reaction products of pectin degradation and their role in non-enzymatic browning reactions should be investigated. In model systems first results show a faster color development of uronic acids in comparison with reducing sugars. However, the hydrolytic and beta-eliminative cleavage does not provide a sufficient explanation. Additionally, the intermediates of the thermal induced degradation of pectins like saturated and 4,5-unsaturated oligogalacturonic acids are not systematically characterized. Regarding to the functional properties of modified pectins, further studies should be of interest. Objective of the project is to investigate and clarify the reaction mechanism of the thermally induced degradation of pectin. More precisely, the influence of the structure of starting materials and conditions used on intermediates formed and their role in color formation by the non-enzymatic browning (Maillard-reaction) should be elucidated. For this reason, different model systems will be used with galacturonic acid and its methyl ester, respectively. The purified partially methyl esterified saturated and unsaturated oligogalacturonic acids should be used separately in further models. Furthermore, the results should provide an insight into the mechanism of pectin degradation and the resultant effect to the physico-chemical characteristics of degradation products. The previously executed differential scanning calorimetry shows anomalies and a mechanism of degradation is postulated. The comparison of chemical investigations and structure-analytical characterizations as a part of the project could confirm our postulated degradation mechanism. Finally, the influence of degradation on functional properties of pectin should be examined. For this reason structures identified by NMR spectroscopy should be compared with results obtained during investigation of physico-chemical properties.