The hidden subtlety of beer foam stability: A blueprint for advanced foam formulations
Emmanouil Chatzigiannakis, Alexandra Alicke, Léa Le Bars, Lucas Bidoire, Jan Vermant
Abstract
It is believed that the structure and properties of protein-rich layers influence beer foam stability through their impact on both surface tension and surface viscosity. However, our experiments employing surface rheometry, tensiometry, and dynamic thin-film balance reveal that the governing mechanism is actually more subtle, and depends on the beer type. While film stability in lager beers does hinge on surface viscosity, as previously reported, Belgian ales (such as Trappist beers) display minimal surface viscosities and instead rely on viscoelastic stresses or Marangoni stresses for stabilization. Especially robust, recirculating Marangoni flows significantly extend film and foam longevity. Moreover, proteomic analyses confirmed that the abundance and specific modifications of lipid transfer protein 1 play a pivotal role in foam stabilization, especially in blond Belgian ales. The strength of Marangoni stresses—and thus foam stability—also depends on the number of fermentations, with triple-fermented Belgian ales outperforming single-fermented ones. Together, these findings offer direct experimental insight into the dynamics of beer foam, facilitating a deeper understanding of foam physics not only in beer but also in other complex surface-active mixtures.