Spring Break
The Truth About Good Head
American Spirits
Timothy Bleasdale
Issue date: 4/17/08 Section: Focus
It is white, frothy and sits between you and your favorite amber libation, but what exactly is head and how does it relate to your beer?. Whether you call it foam or by its proper name, this frothy component of a good brew seems to be causing sharp division in the ranks of beer drinks everywhere. With a little prying, the case for or against head can usually be broke down along the lines of how the drinker is imbibing their beer and why they have chosen to drink beer instead of something else. But at the root of this question, though, is what exactly this foamy substance is and why it is in beer in the first place.
22 And Missing Bill Nye:
For all the nerds over in the North Eagleville science complex, you may want to grab a seat for these next two paragraphs - they're probably the most exciting thing you will ever read in The Daily Campus.
While the most obvious source of head is carbonation, this is definitely not the only cause or else other carbonated beverages like soda and champagne would also develop long-lasting foam. So what's the difference? For this we must look back to the very beginning of beer production. As it turns out, one of the main culprit for this phenomenon is a protein called lipid transfer protein 1 (LTP1) which is found in barley, one of the four main ingredients in beer. By itself, LTP1 and carbon dioxide are not enough to cause the foam. In its natural state, LTP1 is folded into a molecular structure that is not conducive to foam formation. But when brewers set about cooking up beer, they boil together all of the ingredients in beer, aside from the yeast, into a mixture called wort (yeast is later added to the cooled wort to cause fermentation). When the wort is boiled, the heat causes LTP1 to denature or, for the non-nerds, this means the heat causes the protein to change its molecular structure, making it a bit more flexible in terms of bubble formation.
Now let's fast forward through fermentation - you're standing in your kitchen ready to pour out your beer. As long as you've kept the cap on your bottle or refrained from pulling the tab on your can, the carbon dioxide dissolved in your beer has stayed in equilibrium with any bubbles that may have formed (the pressure in the container ensures that gases are reabsorbed into the liquid at the same rate as they pass out). When you pull that tab, you reduce the pressure the beer is under, disrupting this equilibrium allowing for carbon dioxide to more readily leave the solution. This is a simple law of gasses known as Boyle's Law and basically means that if your beer is kept at a constant temperature, the release of pressure will cause the carbon dioxide to expand. When the beer is poured into a glass, the agitation of pouring causes more of the carbon dioxide to be released from solution. As the carbonation begins to be released from the beer it begins to nucleate (this means the carbon dioxide molecule gets together with other carbon dioxide's and forms something like a band, only more bubbly) on small imperfections on the surface of your glass. As these small 'pockets of gas' pass up through the beer, fragments of LTP1 (remember our buddy the protein?) form a filmy structure around the gas, otherwise known as a bubble. Get a bunch of these bubbles forming at once and presto - you get head!
22 And Missing Bill Nye:
For all the nerds over in the North Eagleville science complex, you may want to grab a seat for these next two paragraphs - they're probably the most exciting thing you will ever read in The Daily Campus.
While the most obvious source of head is carbonation, this is definitely not the only cause or else other carbonated beverages like soda and champagne would also develop long-lasting foam. So what's the difference? For this we must look back to the very beginning of beer production. As it turns out, one of the main culprit for this phenomenon is a protein called lipid transfer protein 1 (LTP1) which is found in barley, one of the four main ingredients in beer. By itself, LTP1 and carbon dioxide are not enough to cause the foam. In its natural state, LTP1 is folded into a molecular structure that is not conducive to foam formation. But when brewers set about cooking up beer, they boil together all of the ingredients in beer, aside from the yeast, into a mixture called wort (yeast is later added to the cooled wort to cause fermentation). When the wort is boiled, the heat causes LTP1 to denature or, for the non-nerds, this means the heat causes the protein to change its molecular structure, making it a bit more flexible in terms of bubble formation.
Now let's fast forward through fermentation - you're standing in your kitchen ready to pour out your beer. As long as you've kept the cap on your bottle or refrained from pulling the tab on your can, the carbon dioxide dissolved in your beer has stayed in equilibrium with any bubbles that may have formed (the pressure in the container ensures that gases are reabsorbed into the liquid at the same rate as they pass out). When you pull that tab, you reduce the pressure the beer is under, disrupting this equilibrium allowing for carbon dioxide to more readily leave the solution. This is a simple law of gasses known as Boyle's Law and basically means that if your beer is kept at a constant temperature, the release of pressure will cause the carbon dioxide to expand. When the beer is poured into a glass, the agitation of pouring causes more of the carbon dioxide to be released from solution. As the carbonation begins to be released from the beer it begins to nucleate (this means the carbon dioxide molecule gets together with other carbon dioxide's and forms something like a band, only more bubbly) on small imperfections on the surface of your glass. As these small 'pockets of gas' pass up through the beer, fragments of LTP1 (remember our buddy the protein?) form a filmy structure around the gas, otherwise known as a bubble. Get a bunch of these bubbles forming at once and presto - you get head!
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