Mediwaththe Anushka, Huppertz Thom, Chandrapala Jayani, Vasiljevic Todor
Advanced Food Systems Research Unit, Institute of Sustainable Industries & Liveable Cities, College of Sports, Health and Engineering, Victoria University, Werribee Campus, Werribee, VIC 3030, Australia.
FrieslandCampina, P.O. Box 1551, 3800 Amersfoort, The Netherlands.
Foods. 2024 May 13;13(10):1517. doi: 10.3390/foods13101517.
The effect of shear on heat-induced changes in milk protein concentrate suspensions was examined at different pH levels, revealing novel insights into micellar dissociation and protein aggregation dynamics. Milk protein concentrate suspensions, adjusted to pH of 6.1, 6.4, 6.8, or 7.5, underwent combined heat (90 °C for 5 min or 121 °C for 2.6 min) and shear (0, 100, or 1000 s) treatment. The fragmentation of protein aggregates induced by shear was evident in the control MPC suspensions at pH 6.8, irrespective of the temperature. At pH 7.5, shear increased the heat-induced micellar dissociation. This effect was particularly pronounced at 121 °C and 1000 s, resulting in reduced particle size and an elevated concentration of κ-casein (κ-CN) in the non-sedimentable phase. At pH 6.1 or 6.4, shear effects were dependent on sample pH, thereby modifying electrostatic interactions and the extent of whey protein association with the micelles. At pH 6.1, shear promoted heat-induced aggregation, evidenced by an increase in particle size and a significant decline in both whey proteins and caseins in the non-sedimentable phase. At pH 6.4, shear-induced fragmentation of aggregates was observed, prominently due to comparatively higher electrostatic repulsions and fewer protein interactions. The influence of shear on heat-induced changes was considerably impacted by initial pH.
在不同pH值水平下，研究了剪切力对乳清蛋白浓缩物悬浮液热诱导变化的影响，从而对胶束解离和蛋白质聚集动力学有了新的认识。将乳清蛋白浓缩物悬浮液的pH值调节至6.1、6.4、6.8或7.5，然后进行热（90℃ 5分钟或121℃ 2.6分钟）和剪切（0、100或1000秒）联合处理。在pH 6.8的对照MPC悬浮液中，无论温度如何，剪切诱导的蛋白质聚集体碎片化都很明显。在pH 7.5时，剪切力增加了热诱导的胶束解离。这种效应在121℃和1000秒时尤为明显，导致颗粒尺寸减小，非沉淀相中κ-酪蛋白（κ-CN）浓度升高。在pH 6.1或6.4时，剪切效应取决于样品的pH值，从而改变静电相互作用以及乳清蛋白与胶束的结合程度。在pH 6.1时，剪切促进了热诱导的聚集，这表现为颗粒尺寸增加，非沉淀相中乳清蛋白和酪蛋白均显著下降。在pH 6.4时，观察到剪切诱导的聚集体碎片化，主要是由于相对较高的静电排斥和较少的蛋白质相互作用。剪切对热诱导变化的影响受初始pH值的显著影响。
