Every great pub has beer battered fish and chips as a staple on its menu. It’s crispy golden coating and moist juicy fish make it a firm favourite with patrons. Why is it beer makes such a great batter? You may think because it’s plentiful in a pub that this is reason enough, but as it turns out science has a part to play.
Beer makes such a great base for batter because it simultaneously adds three ingredients—carbon dioxide, foaming agents and alcohol—each of which delivers different aspects of physics and chemistry to make the crust light and crisp.
Beer is saturated with CO2. Unlike most solids (like sugar) which dissolve better in hot liquids than 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 drops considerably and bubbles froth up, expanding the batter mix, and giving it that wonderful crisp texture.
You see, beer forms a head when poured because it contains foaming agents. Some of these agents are proteins that occur naturally in the beer, and some are ingredients that brewers add to produce a creamy, long-lasting head. These compounds form thin films that surround the bubbles and slow the rate at which they burst. This makes foam great thermal insulators, so when the chef slides your beer battered fish portion into the deep fryer, most of the heat is absorbed by the batter rather than the fish. The batter can heat up to 90 degrees Celsius giving the batter its beautiful crispy golden crunch, whilst the delicate fish simmers protected inside.
The alcohol in the beer also plays an important role in moderating the internal temperature and crisping the crust. Alcohol evaporates faster than water, so a beer batter doesn’t have to cook as long as one made only with water or milk. The faster the batter dries, the lower the risk of overcooking the food.
So not only does that batter taste better and fish juicier, but it’s quicker to prepare and serve keeping chef productive and patrons happier!