College of Food Science and Nutritional Engineering, National Engineering Research Center for Fruit and Vegetable Processing, China Agricultural University, Key Lab of Fruit and Vegetable Processing, Ministry of Agriculture and Rural Affairs, Beijing 100083, China.
College of Food Science and Nutritional Engineering, National Engineering Research Center for Fruit and Vegetable Processing, China Agricultural University, Key Lab of Fruit and Vegetable Processing, Ministry of Agriculture and Rural Affairs, Beijing 100083, China; Xinghua Industrial Research Centre for Food Science and Human Health, China Agricultural University, Xinghua 225700, China.
Food Res Int. 2023 Dec;174(Pt 1):113558. doi: 10.1016/j.foodres.2023.113558. Epub 2023 Oct 4.
Micellar casein (MC) has a unique gastric colloidal behavior in response to Ca cross-linking, and its aggregation properties are closely related to pepsin and gastric acid. In this study, MC with different levels of colloidal calcium phosphate (CCP) was obtained by high hydrostatic pressure (HHP) at different pressures, followed by spray drying to obtain the powders. Different amounts of calcium chloride (exogenous Ca) were added to MC powders prior to in vitro simulated digestion to investigate the effect of exogenous serum Ca levels on the aggregation behavior and the structure change of curds generated in gastric tract. The results revealed that HHP induced the emergence of more Ca-binding sites, thus Ca was more likely to bind to MC matrix with low CCP levels. Meanwhile, high serum Ca level provided more opportunities to form aggregates. The Highest pressure (500 MPa) with the highest Ca level (5 mM) caused the lowest solubility aggregates, which were only 30% at the end of gastric digestion (120 min), half of the control sample (0 MPa with 0.15 mM Ca). The results of wide-angle X-ray scattering / small-angle X-ray scattering suggested that both pepsin and gastric acid-induced aggregation via Ca as a bridge. For pepsin, Ca cross-linked between para-κ-casein; For gastric acid, Ca recombined phosphorylation sites and caused cross-linking of casein subunits.
胶束酪蛋白（MC）在钙交联作用下具有独特的胃胶体行为，其聚集特性与胃蛋白酶和胃酸密切相关。本研究采用高压均质（HHP）技术，在不同压力下制备得到不同胶体磷酸钙（CCP）水平的 MC，随后进行喷雾干燥得到粉末。在体外模拟消化前，向 MC 粉末中添加不同量的氯化钙（外源性 Ca），以研究外源性血清 Ca 水平对聚集行为和胃内凝块结构变化的影响。结果表明，HHP 诱导出现更多的 Ca 结合位点，因此更容易与低 CCP 水平的 MC 基质结合。同时，高血清 Ca 水平提供了更多形成聚集的机会。在最高压力（500 MPa）和最高 Ca 水平（5 mM）下，导致最低溶解度的聚集物，在胃消化结束时（120 min）仅为 30%，为对照样品（0 MPa 和 0.15 mM Ca）的一半。广角 X 射线散射/小角 X 射线散射的结果表明，胃蛋白酶和胃酸均通过 Ca 作为桥引发聚集。对于胃蛋白酶，Ca 在副κ-酪蛋白之间交联；对于胃酸，Ca 重新组合磷酸化位点并导致酪蛋白亚基的交联。
