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.

Pulsed electric field technology possesses a high potential and a bright future in food processing to inactivate microorganisms and reduce enzymatic activity. Processed food shows a higher retention of health-related compounds and an extension of the shelf-life compared to conventional pasteurization methods. This technology is gradually moving from the laboratory and pilot-plant scale to the commercial scale. In the current review, we focus on the way existing knowledge on mathematical modeling and computational approaches is structured, connected, and interpreted across scales. We start with the electroporation models, progressing from those that are derived from simple physical and chemical considerations to those that are based on more complex probabilistic approaches. They attempt to predict how electric pulses create pores in cell membranes and form the basis of kinetic inactivation models. Subsequently, we examine the most common kinetic models of microorganism inactivation, from first-order models to models based on random and probabilistic considerations. We then review the works carried out on the numerical simulations of the electric field in a continuous PEF chamber and the works related to coupled simulations of the electric, fluid flow, temperature, and inactivation kinetic field. Finally, we conclude the manuscript with a section dedicated to the current applications of the PEF process to demonstrate its effectiveness.