Institute of Nutrition and Functional Foods (INAF), Dairy Research Centre (STELA), Department of Food Sciences, Université Laval, Québec, Québec, G1V 0A6, Canada.
Institute of Nutrition and Functional Foods (INAF), Dairy Research Centre (STELA), Department of Food Sciences, Université Laval, Québec, Québec, G1V 0A6, Canada.
J Dairy Sci. 2017 Sep;100(9):7071-7082. doi: 10.3168/jds.2017-12774. Epub 2017 Jun 21.
Ultrafiltration (UF) is largely used in the dairy industry to generate milk and whey protein concentrate for standardization of milk or production of dairy ingredients. Recently, it was demonstrated that high hydrostatic pressure (HHP) extended the shelf life of milk and improved rennet coagulation and cheese yield. Pressurization also modified casein micelle size distribution and promoted aggregation of whey proteins. These changes are likely to affect UF performance. Consequently, this study determined the effect of skim milk pressurization (300 and 600 MPa, 5 min) on UF performance in terms of permeate flux decline and fouling. The effect of HHP on milk proteins was first studied and UF was performed in total recycle mode at different transmembrane pressures to determine optimal UF operational parameters and to evaluate the effect of pressurization on critical and limiting fluxes. Ultrafiltration was also performed in concentration mode at a transmembrane pressure of 345 kPa for 130 or 140 min to evaluate the decline of permeate flux and to determine fouling resistances. It was observed that average casein micelle size decreased by 32 and 38%, whereas β-lactoglobulin denaturation reached 30 and 70% at 300 and 600 MPa, respectively. These results were directly related to UF performance because initial permeate fluxes in total recycle mode decreased by 25% at 300 and 600 MPa compared with nonpressurized milk, critical flux, and limiting flux, which were lower during UF of milk treated with HHP. During UF in concentration mode, initial permeate fluxes were 30% lower at 300 and 600 MPa compared with the control, but the total flux decline was higher for nonpressurized milk (62%) compared with pressure-treated milk (30%). Fouling resistances were similar, whatever the treatment, except at 600 MPa where irreversible fouling was higher. Characterization of the fouling layer showed that caseins and β-lactoglobulin were mainly involved in membrane fouling after UF of pressure-treated milk. Our results demonstrate that HHP treatment of skim milk drastically decreased UF performance.
超滤（UF）在乳品行业中被广泛用于生成牛奶和乳清蛋白浓缩物，以实现牛奶标准化或生产乳制品成分。最近，人们证明高静水压（HHP）可以延长牛奶的保质期，并改善凝乳酶凝固和奶酪产量。加压还改变了酪蛋白胶束的大小分布，并促进了乳清蛋白的聚集。这些变化可能会影响 UF 的性能。因此，本研究确定了脱脂牛奶加压（300 和 600 MPa，5 分钟）对 UF 性能的影响，包括渗透通量下降和污染。首先研究了 HHP 对牛奶蛋白的影响，并在不同跨膜压力下以全循环模式进行 UF，以确定最佳 UF 操作参数，并评估加压对临界和限制通量的影响。在 345 kPa 的跨膜压力下还进行了浓缩模式的 UF，持续 130 或 140 分钟，以评估渗透通量的下降并确定污染阻力。结果表明，平均酪蛋白胶束大小分别降低了 32%和 38%，而β-乳球蛋白的变性分别达到了 30%和 70%，在 300 和 600 MPa 下。这些结果与 UF 性能直接相关，因为在全循环模式下，初始渗透通量分别比未加压牛奶降低了 25%，在 300 和 600 MPa 下，临界通量和限制通量也较低，这是由于 HHP 处理的牛奶 UF 过程中。在浓缩模式下 UF 时，与对照相比，在 300 和 600 MPa 下初始渗透通量降低了 30%，但非加压牛奶的总通量下降（62%）高于加压处理牛奶（30%）。污染阻力相似，无论处理方式如何，除了在 600 MPa 下，不可逆污染更高。污染层的特性表明，在 UF 处理后的压力处理牛奶中，主要是酪蛋白和β-乳球蛋白参与了膜污染。我们的研究结果表明，HHP 处理脱脂牛奶会大大降低 UF 的性能。
