Luz Sanz María, Corzo-Martínez Marta, Rastall Robert A, Olano Agustín, Moreno F Javier
Instituto de Química Orgánica General (CSIC), C/ Juan de la Cierva 3, 28006 Madrid, Spain.
J Agric Food Chem. 2007 Sep 19;55(19):7916-25. doi: 10.1021/jf071111l. Epub 2007 Aug 21.
Galactooligosaccharides (GOS) are well-known prebiotic ingredients which can form the basis of new functional dairy products. In this work, the production and characterization of glycated beta-lactoglobulin (beta-LG) with prebiotic GOS through the Maillard reaction under controlled conditions ( a(w) = 0.44, 40 degrees C for 23 days) have been studied. The extent of glycation of beta-LG was evaluated by formation of furosine which progressively increased with storage for up to 16 days, suggesting that the formation of Amadori compounds prevailed over their degradation. RP-HPLC-UV, SDS-PAGE, and IEF profiles of beta-LG were modified as a consequence of its glycation. MALDI-ToF mass spectra of glycated beta-LG showed an increase of up to approximately 21% in its average molecular mass after storage for 23 days. Moreover, a decrease in unconjugated GOS (one tri-, two tetra-, and one pentasaccharide) was observed by HPAEC-PAD upon glycation. These results were confirmed by ESI MS. The stability of the glycated beta-LG to in vitro simulated gastrointestinal digestion was also described and compared with that of the unglycated protein. The yield of digestion products of glycated beta-LG was lower than that observed for the unglycated protein. The conjugation of prebiotic carbohydrates to stable proteins and peptides could open new routes of research in the study of functional ingredients.
低聚半乳糖（GOS）是著名的益生元成分，可构成新型功能性乳制品的基础。在本研究中，对在可控条件下（水分活度(a(w)=0.44)，40℃，23天）通过美拉德反应生成的益生元GOS糖化β-乳球蛋白（β-LG）进行了制备和表征。通过测定糖基化终产物（furosine）的生成量来评估β-LG的糖基化程度，其生成量随储存时间延长至16天逐渐增加，这表明阿马多里化合物的生成量超过了其降解量。由于β-LG发生了糖基化，其反相高效液相色谱-紫外（RP-HPLC-UV）、十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（SDS-PAGE）和等电聚焦（IEF）图谱均发生了改变。糖基化β-LG的基质辅助激光解吸电离飞行时间质谱（MALDI-ToF）显示，储存23天后其平均分子量增加了约21%。此外，通过高效阴离子交换色谱-脉冲安培检测法（HPAEC-PAD）观察到，糖基化后未结合的GOS（一种三糖、两种四糖和一种五糖）减少。这些结果通过电喷雾质谱（ESI MS）得到了证实。还描述了糖基化β-LG在体外模拟胃肠道消化中的稳定性，并与未糖基化蛋白进行了比较。糖基化β-LG的消化产物产率低于未糖基化蛋白。益生元碳水化合物与稳定的蛋白质和肽的结合可能为功能性成分的研究开辟新的研究途径。
