Why does the “head” of foam when you pour a soda dissipate within a few seconds, but on many beers it lasts much longer?
In: Chemistry
Soda doesn’t have much in it. Just sugar and water and little bits of flavor. Beer had tons of material left from the grain its made of, so there is lots more structure.
Beer’s protein content contributes to its foamy head by increasing surface tension. Unlike other carbonated drinks lacking protein, beer forms a distinct head due to this property. This phenomenon is akin to whipping egg whites, which also become foamy due to their protein content.
Additionally, some beers are nitrogenated rather than carbonated. Because nitrogen is less prone to escaping a liquid than carbon dioxide, the bubbles in nitrogenated beers, such as Guinness, are more persistent. This characteristic imparts the creamy texture and prolonged bubbliness characteristic of such brews.
Soda are primary water and sugar and it do not form stable bubbles. Beer contain stuff that do, that is protein, hop resins, and yeast. What that does is make it harder for the bubble to pop. wiped cream is the same phenomena. What is mixed in the water will stop it from moving. It is about [https://en.wikipedia.org/wiki/Colloid](https://en.wikipedia.org/wiki/Colloid) stability.
Gelatine is a extreme example of this that, the mixture is around 50x more water the gelatine powder and if feel quite stable material. Gelatine is made of proteins that has been a bit processed.
The magic word here is ‘surfactants’. Google it, basically ingredients that are active at surfaces and alter the surface tension and stability.
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