Foam also carries a profound trigeminal sensation—that is, “taste” effects which are actually perceived physically. Think of the “cool” sensation of mint, or the “hot” sensation of chili peppers. Neither is delivering an actual thermal load, but rather they cause a physical perception. The creamy, fluffy feel of foam can dramatically alter the perception of any given beer by “softening” the overall palate. It’s also important to remember that our senses of taste and smell are intimately interwoven. In fact, many times a specific characteristic that a drinker may describe as ‘taste’ is actually detected in their nasal passage. Foam brings more odor compounds to the surface of your beer, kind of like un-stuffing your nose and opening up the full range of flavors. The proteins form a coating around every foam bubble, interact with other compounds that also happen to rise to the top of your glass. Once these proteins and compounds begin to interact with one another, they become denser, undergoing a textural transition, and begin to stick to the sides of the glass when left alone for a bit. This is why a beer consumed slowly will accumulate much more lacing than its guzzled counterpart.
How to pour beer:
Belgian (or Brussels) lace:
The latticework of foam from the head of the beer that is left on the glass after a drink of beer has been taken. Reflects both the care taken in brewing the beer and the cleanliness of the glass from which it is being served.