Department of Food Science and Technology, The Ohio State University, Columbus 43210.
Department of Food Science and Technology, The Ohio State University, Columbus 43210; Department of Food Agricultural and Biological Engineering, The Ohio State University, Columbus 43210.
J Dairy Sci. 2021 Feb;104(2):1531-1547. doi: 10.3168/jds.2020-19081. Epub 2020 Dec 11.
The effects of pressure, temperature, shear, and their interactions on selected quality attributes and stability of milk during ultra-shear technology (UST) were investigated. The UST experiments include pressure (400 MPa) treatment of the milk sample preconditioned at 2 different initial temperatures (25°C and 15°C) and subsequently depressurizing it via a shear valve at 2 flow rates (low: 0.15-0.36 g/s; high: 1.11-1.22 g/s). Raw milk, high-pressure processed (HPP; 400 MPa, ~40°C for 0 and 3 min) and thermal treated (72°C for 15 s) milk samples served as the controls. The effect of different process parameters on milk quality attributes were evaluated using particle size, zeta potential, viscosity, pH, creaming, lipase activity, and protein profile. The HPP treatment did not cause apparent particle size reduction but increased the sample viscosity up to 3.08 mPa·s compared with 2.68 mPa·s for raw milk. Moreover, it produced varied effects on creaming and lipase activity depending on hold time. Thermal treatment induced slight reduction in particle size and creaming as compared with raw milk. The UST treatment at 35°C reduced the effective diameter of sample particles from 3,511.76 nm (raw milk) to 291.45 nm. This treatment also showed minimum relative lipase activity (29.93%) and kept milk stable by preventing creaming. The differential effects of pressure, shear, temperature, and their interactions were evident, which would be useful information for equipment developers and food processors interested in developing improved food processes for dairy beverages.
研究了超剪切技术（UST）过程中压力、温度、剪切及其相互作用对牛奶某些质量属性和稳定性的影响。UST 实验包括在 2 种初始温度（25°C 和 15°C）下对牛奶样品进行预处理，然后在 2 种流速（低：0.15-0.36 g/s；高：1.11-1.22 g/s）下通过剪切阀对其进行减压，从而对牛奶样品进行压力（400 MPa）处理。生牛乳、高压处理（400 MPa，40°C，0 和 3 min）和热处理（72°C，15 s）的牛奶样品作为对照。使用粒径、ζ 电位、粘度、pH 值、乳脂上浮、脂肪酶活性和蛋白质图谱评估不同工艺参数对牛奶质量属性的影响。与生牛乳（2.68 mPa·s）相比，HPP 处理不会明显减小粒径，但会将样品粘度增加至 3.08 mPa·s。此外，根据持留时间，其对乳脂上浮和脂肪酶活性产生不同的影响。与生牛乳相比，热处理会略微减小粒径和乳脂上浮。在 35°C 下进行 UST 处理会使样品颗粒的有效直径从 3,511.76 nm（生牛乳）减小至 291.45 nm。这种处理方法还表现出最低的相对脂肪酶活性（29.93%），通过防止乳脂上浮使牛奶保持稳定。压力、剪切、温度及其相互作用的差异效应很明显，这对于有兴趣开发乳制品饮料改良食品工艺的设备开发者和食品加工者来说是有用的信息。
