Beer, Beer, Beer, Beer

So.. I am out for a couple of cheeky shandies this evening, and we all kinda got talking about beer and pubs and stuff.  Specifically we began to ponder why does beer go flat when it gets warm?

Have you ever pondered that yourself?
Well, we did a bit of research and found out the following:

It all comes down to the behaviour of gases and their solubility in water.  Most beers dilute solutions of sugars, gases, organic acids and other complex compounds and, of course, alcohols.

The gas which gives fizzy drinks their bubbles is Carbon Dioxide (that's CO2, to you).  In the case of beardy-weirdy real ales, the CO2 is generated by the action of yeasts on residual sugars in the drink, whereas in most beers -specifically lager- the conditioning gas is added artificially at the brewery or at the point of sale.

The problem arises because the solubility of CO2 is related to the temperature of the solvent in which it is dissolved.  More gas can dissolve in cold beer than in warm beer.  This is also why fish such as trout and salmon, which need a lot of oxygen, live in cold mountain streams and rivers because the amount of oxygen dissolved in these environments is so much higher.

When beer is served from the pump, it will contain a certain concentration of CO2 but, as the drink heats up under the influence of a sweaty (?) hand in a warm room, its ability to hold its CO2 in solution decreases. The excess gas is then released into the atmosphere through the bubbles that you see rising in the beer, and the drink consequently goes flat.  Other volatile compounds from the malt and hops vaporise faster and you may notice that the beer also smells different.

So there you go.. if you want fizzy beer drink it quickly or sit in a cold pub, not allowing your sweaty palms anywhere near it..