Department of Food Science, Cornell University, Ithaca, NY 14853.
Department of Food Science, Rutgers University, New Brunswick, NJ 08901.
J Dairy Sci. 2017 Sep;100(9):7055-7070. doi: 10.3168/jds.2016-12072. Epub 2017 Jun 21.
Reconstituted micellar casein concentrates and milk protein concentrates of 2.5 and 10% (wt/vol) protein concentration were subjected to high-pressure processing at pressures from 150 to 450 MPa, for 15 min, at ambient temperature. The structural changes induced in milk proteins by high-pressure processing were investigated using a range of physical, physicochemical, and chemical methods, including dynamic light scattering, rheology, mid-infrared spectroscopy, scanning electron microscopy, proteomics, and soluble mineral analyses. The experimental data clearly indicate pressure-induced changes of casein micelles, as well as denaturation of serum proteins. Calcium-binding α- and α-casein levels increased in the soluble phase after all pressure treatments. Pressurization up to 350 MPa also increased levels of soluble calcium and phosphorus, in all samples and concentrations, whereas treatment at 450 MPa reduced the levels of soluble Ca and P. Experimental data suggest dissociation of calcium phosphate and subsequent casein micelle destabilization as a result of pressure treatment. Treatment of 10% micellar casein concentrate and 10% milk protein concentrate samples at 450 MPa resulted in weak, physical gels, which featured aggregates of uniformly distributed, casein substructures of 15 to 20 nm in diameter. Serum proteins were significantly denatured by pressures above 250 MPa. These results provide information on pressure-induced changes in high-concentration protein systems, and may inform the development on new milk protein-based foods with novel textures and potentially high nutritional quality, of particular interest being the soft gel structures formed at high pressure levels.
将浓度为 2.5%和 10%（wt/vol）的重组胶束酪蛋白浓缩物和乳蛋白浓缩物在环境温度下用 150 至 450 MPa 的压力处理 15 分钟。使用一系列物理、物理化学和化学方法研究了高压处理对乳蛋白引起的结构变化，包括动态光散射、流变学、中红外光谱、扫描电子显微镜、蛋白质组学和可溶性矿物质分析。实验数据清楚地表明，高压处理会引起酪蛋白胶束的变化以及血清蛋白的变性。在所有压力处理后，可溶相中α-和α-酪蛋白的钙结合水平增加。在所有样品和浓度下，加压至 350 MPa 也会增加可溶性钙和磷的水平，而在 450 MPa 下处理会降低可溶性 Ca 和 P 的水平。实验数据表明，由于压力处理，磷酸钙解离，随后导致酪蛋白胶束不稳定。在 450 MPa 下处理 10%胶束酪蛋白浓缩物和 10%乳蛋白浓缩物样品会导致形成弱的物理凝胶，其特征是直径为 15 至 20nm 的均匀分布的酪蛋白亚结构的聚集体。血清蛋白在压力超过 250 MPa 时会发生明显变性。这些结果提供了有关高浓度蛋白质系统中压力诱导变化的信息，并可能为开发具有新型质地和潜在高营养价值的新型乳蛋白基食品提供信息，特别感兴趣的是在高压水平下形成的软凝胶结构。
