Wegener Steffen, Kaufmann Martin, Kroh Lothar W
Institute of Food Technology and Food Chemistry, Technical University of Berlin, Gustav-Meyer-Allee 25, 13355 Berlin, Germany.
Food Chem. 2017 Oct 1;232:450-454. doi: 10.1016/j.foodchem.2017.04.046. Epub 2017 Apr 7.
Heating aqueous d-glucose model reactions with l-glutamine and l-alanine yielded similar colored solutions. However, size-exclusion chromatography (SEC) revealed that both non-enzymatic browning reactions proceeded differently. Due to a fast occurring cyclization of l-glutamine to pyroglutamic acid, the typical amino-carbonyl reaction was slowed down. However, l-glutamine and l-alanine model reactions showed the same browning index. Closer investigations could prove that l-pyroglutamic acid was able to influence non-enzymatic browning reactions. SEC analyses of d-glucose model reactions with and without l-pyroglutamic acid revealed an increase of low molecular colored compounds in the presence of l-pyroglutamic acid. Polarimetric measurements showed a doubling of d-glucose mutarotation velocity and HPLC analyses of d-fructose formation during thermal treatment indicated a tripling of aldose-ketose transformation in the presence of l-pyroglutamic acid, which are signs of a faster proceeding non-enzymatic browning process. 2-Pyrrolidone showed no such behavior, thus the additional carboxylic group should be responsible for the observed effects.
用l-谷氨酰胺和l-丙氨酸对d-葡萄糖水溶液模型反应进行加热，得到了相似的有色溶液。然而，尺寸排阻色谱（SEC）显示，两种非酶褐变反应的进行方式有所不同。由于l-谷氨酰胺快速环化生成焦谷氨酸，典型的氨基-羰基反应减缓。然而，l-谷氨酰胺和l-丙氨酸模型反应显示出相同的褐变指数。进一步研究可以证明，l-焦谷氨酸能够影响非酶褐变反应。对含有和不含l-焦谷氨酸的d-葡萄糖模型反应进行SEC分析，结果显示在l-焦谷氨酸存在下，低分子有色化合物有所增加。旋光测量表明，d-葡萄糖变旋速度加倍，对热处理过程中d-果糖形成的HPLC分析表明，在l-焦谷氨酸存在下，醛糖-酮糖转化增加了两倍，这是非酶褐变过程加快的迹象。2-吡咯烷酮没有表现出这种行为，因此额外的羧基应该是造成上述观察结果的原因。
