Liu Fahui, Teodorowicz Małgorzata, van Boekel Martinus A J S, Wichers Harry J, Hettinga Kasper A
Food Quality & Design Group, Wageningen University & Research Centre, 6700EV Wageningen, The Netherlands.
Cell Biology and Immunology Group, Wageningen University and Research Centre, 6708WD Wageningen, The Netherlands.
Food Funct. 2016 Jan;7(1):239-49. doi: 10.1039/c5fo00718f.
Heat treatment is the most common way of milk processing, inducing structural changes as well as chemical modifications in milk proteins. These modifications influence the immune-reactivity and allergenicity of milk proteins. This study shows the influence of dry heating on the solubility, particle size, loss of accessible thiol and amino groups, degree of Maillard reaction, IgG-binding capacity and binding to the receptor for advanced glycation end products (RAGE) of thermally treated and glycated whey proteins. A mixture of whey proteins and lactose was dry heated at 130 °C up to 20 min to mimic the baking process in two different water activities, 0.23 to mimic the heating in the dry state and 0.59 for the semi-dry state. The dry heating was accompanied by a loss of soluble proteins and an increase in the size of dissolved aggregates. Most of the Maillard reaction sites were found to be located in the reported conformational epitope area on whey proteins. Therefore the structural changes, including exposure of the SH group, SH-SS exchange, covalent cross-links and the loss of available lysine, subsequently resulted in a decreased IgG-binding capacity (up to 33%). The binding of glycation products to RAGE increased with the heating time, which was correlated with the stage of the Maillard reaction and the decrease in the IgG-binding capacity. The RAGE-binding capacity was higher in samples with a lower water activity (0.23). These results indicate that the intensive dry heating of whey proteins as it occurs during baking may be of importance to the immunological properties of allergens in cow's milk, both due to chemical modifications of the allergens and formation of AGEs.
热处理是牛奶加工最常见的方式，会引起牛奶蛋白质的结构变化以及化学修饰。这些修饰会影响牛奶蛋白质的免疫反应性和致敏性。本研究显示了干热对热处理和糖基化乳清蛋白的溶解度、粒径、可及巯基和氨基的损失、美拉德反应程度、IgG结合能力以及与晚期糖基化终产物受体（RAGE）结合的影响。将乳清蛋白和乳糖的混合物在130℃干热长达20分钟，以模拟两种不同水分活度下的烘焙过程，水分活度0.23模拟干燥状态下的加热，0.59模拟半干燥状态。干热伴随着可溶性蛋白质的损失以及溶解聚集体尺寸的增加。发现大多数美拉德反应位点位于乳清蛋白上已报道的构象表位区域。因此，包括巯基暴露、巯基-二硫键交换、共价交联以及可用赖氨酸的损失在内的结构变化，随后导致IgG结合能力降低（高达33%）。糖基化产物与RAGE的结合随加热时间增加，这与美拉德反应阶段以及IgG结合能力的降低相关。在水分活度较低（0.23）的样品中，RAGE结合能力更高。这些结果表明，烘焙过程中发生的乳清蛋白强烈干热可能对牛奶中过敏原的免疫学特性具有重要意义，这既是由于过敏原的化学修饰，也是由于晚期糖基化终产物的形成。
