Experimental and numerical investigation of beer foam

Abstract

The frothy foam on top of beer is produced by bubbles of gas, predominantly carbon dioxide, rising to the surface. The chemical components that produce the head are wort protein, yeast, and hop residue. This involves a large number of chemical components and numerous physical interactions. The beer foam and, especially, its stability is an essential quality characteristic of a beer. A consumer defines a beer's head by its stability, quantity, lacing (glass adhesion or cling), whiteness, creaminess, and strength. To achieve an accurate prediction of beer foam formation and collapse is challenging because complex numerical models are required to account for these nonlinear beer foam effects. To analyze a new design of a beer bottom-to-top pouring system for the startup company Einstein 1, we first set up the experimental tests of this pouring system. Afterward, we performed the associated repeatability studies to achieve stable working conditions. To study beer foam formation and its collapse, we employed a multiphase Reynolds-averaged Navier–Stokes solver that considered two inter-penetrating continua, which allowed accounting for multi-component phases and mass and heat transfer between these phases. We numerically and experimentally investigated beer foam patterns, beer heights, beer/foam ratio, foam height, foam stability, and foam volume fractions. We performed grid sensitivity studies and validated the numerical solver by comparing results against model test measurements. The results indicated that that the higher the temperature of the beer and the higher the tap pressure is, the greater the foam development and the associated foam height are but not necessarily the foam stability.