Laboratory of Food Chemistry, Wageningen UR, Bornse Weilanden 9, Wageningen 6708, WG, the Netherlands.
Department of Chemical and Pharmaceutical Engineering, Sofia University, Bulgaria.
Adv Colloid Interface Sci. 2023 Feb;312:102845. doi: 10.1016/j.cis.2023.102845. Epub 2023 Jan 23.
The stability of foams is commonly linked to the interfacial properties of the proteins and other surfactants used. This study aimed to use these relationships to explain differences in foam stability observed among similar beer samples from different breweries. The foam stability was different for each sample (Nibem foam stability ranged from 206 to 300 s), but ranking was similar for all three foaming methods used, thus independent of the method, gas, etc. Differences in foam stability were dominated by differences in coalescence, as illustrated by the correlation with the stability of single bubbles and thin liquid films. The differences in coalescence stability could not be explained by the measured interfacial properties (e.g. surface pressure, adsorption rate, dilatational modulus and surface shear viscosity), or the bulk properties (concentration, pH, ionic strength, viscosity), since they were similar for all samples. The drainage rates and disjoining pressure isotherms measured in thin liquid films were also similar for all samples, further limiting the options to explain the differences in foam stability using known arguments. The differences in coalescence stability of the thin films was shown to depend on the liquid in between the adsorbed layers of the thin film, using a modified capillary cell to exchange this liquid (to a buffer, or one of the other samples). This illustrates the need to review our current understanding and to develop new methods both for experimental study and theoretical description, to better understand foam stability in the future.
泡沫的稳定性通常与所使用的蛋白质和其他表面活性剂的界面特性有关。本研究旨在利用这些关系来解释不同啤酒厂生产的类似啤酒样品之间观察到的泡沫稳定性差异。每个样品的泡沫稳定性都不同（Nibem 泡沫稳定性范围为 206 到 300 秒），但三种起泡方法的排序相似，因此与方法、气体等无关。泡沫稳定性的差异主要由聚并差异决定，这可以通过与单个气泡和薄液膜稳定性的相关性得到证明。聚并稳定性的差异不能用测量的界面特性（如表面压力、吸附速率、扩张模量和表面剪切粘度）或体相特性（浓度、pH 值、离子强度、粘度）来解释，因为所有样品的这些特性都相似。所有样品的薄液膜排水率和推斥压力等温线也相似，这进一步限制了使用已知论点来解释泡沫稳定性差异的选择。通过使用改良的毛细管池交换薄液膜中吸附层之间的液体（缓冲液或其他样品之一），显示出薄液膜聚并稳定性的差异取决于吸附层之间的液体。这说明了需要重新审视我们目前的理解，并开发新的实验研究和理论描述方法，以便在未来更好地理解泡沫稳定性。
