Beer Batter is Better; February 2011; Scientific American Magazine; by W. Wayt Gibbs, Nathan Myhrvold; 1 Page(s)

If you’ve ever sat down at a pub to a plate of really good fish and chips—the kind in which the fish stays tender and juicy but the crust is supercrisp—odds are that the cook used beer as the main liquid when making the batter. Beer makes such a great base for batter because it simultaneously adds three ingredients—carbon dioxide, foaming agents and alcohol—each of which brings to bear different aspects of physics and chemistry to make the crust light and crisp.

Beer is saturated with CO₂. Unlike most solids, like salt and sugar, which dissolve better in hot liquids than they do in cold, gases dissolve more readily at low temperatures. Put beer into a batter mix, and when the batter hits the hot oil, the solubility of the CO₂ plummets, and bubbles froth up, expanding the batter mix and lending it a lacy, crisp texture.