Abstract Soluble beer proteins are heat-stable proteins from malted barley. These proteins are mainly composed of proteins that would be involved in the defense of barley against microbial pathogens as a serpin-like cysteine protease inhibitor (protein Z) and lipid transfer proteins (LTPs). These proteins are essential for the formation of beer foam. To become surface active these barley proteins undergo a structural maturation including glycation through Maillard reaction on malting and unfolding on heating during the brewing process. In the case of LTP1, another modification involves an acylation by a product of the activity of two enzymes from barley embryo (i.e. lipoxygenase and allene oxide synthase) on polyunsaturated fatty acids. These structural modifications increase the amphiphilic character of the proteins and their spreading behavior at the gas–liquid interfaces. Finally, minor beer proteins, weakly soluble in water, barley storage proteins (i.e. hordeins) are responsible for the haze formation of freshly fermented beer.