Güell Carme, Ferrando Montserrat, Trentin Alexandre, Schroën Karin
Departament d'Enginyeria Química, Universitat Rovira i Virgili, Avda. Països Catalans 26, Tarragona 43007, Spain.
Food Process Engineering Group, Wageningen University, Bornse Weilanden 9, 6708 WG Wageningen, The Netherlands.
Membranes (Basel). 2017 Mar 25;7(2):19. doi: 10.3390/membranes7020019.
Proteins are mostly used to stabilize food emulsions; however, production of protein containing emulsions is notoriously difficult to capture in scaling relations due to the complex behavior of proteins in interfaces, in combination with the dynamic nature of the emulsification process. Here, we investigate premix membrane emulsification and use the Ohnesorge number to derive a scaling relation for emulsions prepared with whey protein, bovine serum albumin (BSA), and a standard emulsifier Tween 20, at various concentrations (0.1%, 0.5%, 1.25% and 2%). In the Ohnesorge number, viscous, inertia, and interfacial tension forces are captured, and most of the parameters can be measured with great accuracy, with the exception of the interfacial tension. We used microfluidic Y-junctions to estimate the apparent interfacial tension at throughputs comparable to those in premix emulsification, and found a unifying relation. We next used this relation to plot the Ohnesorge number versus P-ratio defined as the applied pressure over the Laplace pressure of the premix droplet. The measured values all showed a decreasing Ohnesorge number at increasing P-ratio; the differences between regular surfactants and proteins being systematic. The surfactants were more efficient in droplet size reduction, and it is expected that the differences were caused by the complex behavior of proteins in the interface (visco-elastic film formation). The differences between BSA and whey protein were relatively small, and their behavior coincided with that of low Tween concentration (0.1%), which deviated from the behavior at higher concentrations.
蛋白质大多用于稳定食品乳液；然而，由于蛋白质在界面中的复杂行为，再加上乳化过程的动态性质，含蛋白质乳液的生产很难用比例关系来描述。在此，我们研究预混膜乳化，并使用奥内佐格数来推导用乳清蛋白、牛血清白蛋白（BSA）和标准乳化剂吐温20在不同浓度（0.1%、0.5%、1.25%和2%）下制备的乳液的比例关系。在奥内佐格数中，粘性力、惯性力和界面张力都被考虑在内，除了界面张力外，大多数参数都可以非常精确地测量。我们使用微流体Y型交叉通道来估计在与预混乳化相当的通量下的表观界面张力，并发现了一个统一的关系。接下来，我们用这个关系绘制奥内佐格数与P比的关系图，P比定义为施加压力与预混液滴拉普拉斯压力的比值。测量值都显示，随着P比增加，奥内佐格数减小；常规表面活性剂和蛋白质之间的差异是系统性的。表面活性剂在减小液滴尺寸方面更有效，预计这些差异是由蛋白质在界面中的复杂行为（形成粘弹性膜）引起的。BSA和乳清蛋白之间的差异相对较小，它们的行为与低浓度吐温（0.1%）的行为一致，这与较高浓度时的行为不同。
