Adams Michael C, Barbano David M
Northeast Dairy Foods Research Center, Department of Food Science, Cornell University, Ithaca, NY 14853.
Northeast Dairy Foods Research Center, Department of Food Science, Cornell University, Ithaca, NY 14853.
J Dairy Sci. 2016 Jan;99(1):167-82. doi: 10.3168/jds.2015-9897. Epub 2015 Oct 29.
Our objective was to determine the effect of retentate flow channel diameter (4 or 6mm) of nongraded permeability 100-nm pore size ceramic membranes operated in nonuniform transmembrane pressure mode on the limiting retentate protein concentration (LRPC) while microfiltering (MF) skim milk at a temperature of 50°C, a flux of 55 kg · m(-2) · h(-1), and an average cross-flow velocity of 7 m · s(-1). At the above conditions, the retentate true protein concentration was incrementally increased from 7 to 11.5%. When temperature, flux, and average cross-flow velocity were controlled, ceramic membrane retentate flow channel diameter did not affect the LRPC. This indicates that LRPC is not a function of the Reynolds number. Computational fluid dynamics data, which indicated that both membranes had similar radial velocity profiles within their retentate flow channels, supported this finding. Membranes with 6-mm flow channels can be operated at a lower pressure decrease from membrane inlet to membrane outlet (ΔP) or at a higher cross-flow velocity, depending on which is controlled, than membranes with 4-mm flow channels. This implies that 6-mm membranes could achieve a higher LRPC than 4-mm membranes at the same ΔP due to an increase in cross-flow velocity. In theory, the higher LRPC of the 6-mm membranes could facilitate 95% serum protein removal in 2 MF stages with diafiltration between stages if no serum protein were rejected by the membrane. At the same flux, retentate protein concentration, and average cross-flow velocity, 4-mm membranes require 21% more energy to remove a given amount of permeate than 6-mm membranes, despite the lower surface area of the 6-mm membranes. Equations to predict skim milk MF retentate viscosity as a function of protein concentration and temperature are provided. Retentate viscosity, retentate recirculation pump frequency required to maintain a given cross-flow velocity at a given retentate viscosity, and retentate protein determination by mid-infrared spectrophotometry were all useful tools for monitoring the retentate protein concentration to ensure a sustainable MF process. Using 6-mm membranes instead of 4-mm membranes would be advantageous for processors who wish to reduce energy costs or maximize the protein concentration of a MF retentate.
我们的目标是确定在50°C的温度、55 kg·m⁻²·h⁻¹的通量和7 m·s⁻¹的平均错流速度下，以非均匀跨膜压力模式运行的孔径为100 nm的非分级渗透陶瓷膜的截留液流道直径（4或6mm）对极限截留液蛋白质浓度（LRPC）的影响，同时对脱脂乳进行微滤（MF）。在上述条件下，截留液中的真实蛋白质浓度从7%逐步增加到11.5%。当温度、通量和平均错流速度得到控制时，陶瓷膜截留液流道直径不会影响LRPC。这表明LRPC不是雷诺数的函数。计算流体动力学数据表明，两种膜在其截留液流道内具有相似的径向速度分布，支持了这一发现。与4mm流道的膜相比，6mm流道的膜可以在从膜入口到膜出口的压力降（ΔP）更低的情况下运行，或者在更高的错流速度下运行，具体取决于控制的参数。这意味着在相同的ΔP下，由于错流速度的增加，6mm的膜比4mm的膜能够实现更高的LRPC。理论上，如果膜不截留血清蛋白，6mm膜更高的LRPC可以在两个微滤阶段实现95%的血清蛋白去除，且阶段间进行渗滤。在相同的通量、截留液蛋白质浓度和平均错流速度下，尽管6mm膜的表面积较小，但与6mm膜相比，4mm膜去除给定体积渗透物所需的能量多21%。提供了预测脱脂乳微滤截留液粘度作为蛋白质浓度和温度函数的方程。截留液粘度、在给定截留液粘度下维持给定错流速度所需的截留液再循环泵频率以及通过中红外分光光度法测定截留液蛋白质，都是监测截留液蛋白质浓度以确保可持续微滤过程的有用工具。对于希望降低能源成本或使微滤截留液的蛋白质浓度最大化的加工商来说，使用6mm的膜而不是4mm的膜将具有优势。
