Researchers at ETH Zurich have discovered why Belgian beers such as Tripels and Doubles have a more stable head than lagers. It has to do with the specific brewing process and refermentation. ‘Beers are teaching us what the most efficient way to keep foam stable is. This is a source of inspiration for other materials,’ says Jan Vermant, chemical engineer and one of the researchers.
New study reveals the mystery of why Belgian beers have such a magnificent head
Colin Clapson
Published:
For many beer lovers, nothing beats a thick head. But the exact mechanisms behind such a perfect, “stable” head were not yet known. Until now.
According to Jan Vermant, chemical engineer at ETH Zurich, it is not only the way you pour that matters. ‘The intrinsic stability of the foam depends on the type of beer,’ he tells VRT News.
Pilsner vs. Double vs. Triple
To arrive at this conclusion, he and his fellow researchers compared four Belgian abbey and Trappist beers, namely Tripel Karmeliet, Westmalle Extra, Westmalle Dubbel and Westmalle Tripel, with two Swiss pilsners, Feldschlösschen and Chopfab.
Beer foam consists of small air bubbles separated by thin layers of liquid. These thin layers must remain stable, otherwise the bubbles burst and the foam collapses. ‘For simple pilsners, it is well known that the number of proteins and the viscosity they cause determine the head.’
But that does not apply to Belgian beers, the researchers found. Other processes are at work there. ‘Belgian beers use “smarter” ways to keep the foam stable,’ Vermant explains.
This has everything to do with the brewing process, including fermentation. 'The more intense the fermentation, the higher the alcohol content. This releases more proteins. There are also more modifications of those proteins. Beers such as a Double do not form a syrupy surface, as pilsners do, but rather an elastic membrane.' The membrane can cause mechanical tension, which protects the gas bubbles from deformation. That is why the foam of a Double remains more intact.
But the “winner” with the most stable foam is the Triple. ‘There we saw a big surprise: the syrupiness disappeared completely and the mechanism changed totally.’ Marangoni stresses, which also cause typical “tears” on a wine glass, in particular are responsible for the exceptionally stable head of a Triple.
From fire extinguishers to plant-based milk
This knowledge can help you change the foam stability of beer in a more targeted way and that has attracted great interest from the breweries. But the usefulness of the discovery goes beyond just a perfect foam layer.
First and foremost, the research team wanted to learn more about foam formation in general, and beer was the perfect medium for this. ‘Beer teaches us the most efficient way to keep foam stable. This is a source of inspiration for other materials.’
In particular, the mechanism that occurs in Double beer can be used for other purposes. ‘The question becomes: can you design other strategies like the ones used in Double beer, namely by creating elastic membranes?’
This could bear fruit in many different sectors. Think of concrete with bubbles that is more resistant to frost, easily foaming plant-based milk or PFAS-free fire extinguishers. ‘Inspiration comes from looking deep into a beer’s foam rather than deep into a glass,’ concludes Vermant.