It often surprises people when I tell them that I don't drink a particular beer because it's not vegetarian.
"How could beer not be vegetarian?" is the invariably bemused reply.
As a vegan, I avoid beers that contain animal products, including honey and lactose (milk/sweet stouts, for example). But even fellow vegetarians are often baffled by the concept that many beers —and wines — are produced with ingredients that come from cows, pigs, and fish.
You see, the clarity of beer and wine has always been a big focus of producers. While a little haze in a finished beer has no effect on its flavor, a clear beer is often considered more attractive than a cloudy or opaque one. To that end, breweries have long used fining (or clarifying) agents to refine the appearance of their product.
The most common animal-derived fining agent is isinglass, a collagen derived from the swim bladder of various species of fish, especially sturgeon and cod. This is a traditional ingredient used primarily in British beers, especially cask ales. Isinglass works by binding to floating yeast and protein particles and precipitating to the bottom of the vessel in a jellylike mass, separating them from the now-clear beer.
Gelatin is a similar product, used more commonly in domestic craft beers. I specify craft beers because none of the big-name domestic brewers use animal-based fining agents. Like isinglass, gelatin is used after fermentation is complete to precipitate haze-forming particles from suspension. Gelatin is a collagen product derived from the skin, bones, and connective tissue of various animals, mostly pigs and cows, and is the same as the stuff you'll find on the grocery store shelf.
While isinglass and gelatin are traditional and widely-used fining agents, many beers are produced without any fining agents at all, most notably all German beers that adhere to the traditional brewing regulations known as the Reinhotsgebot and nearly all Belgian beers.
Perhaps the most common fining agent of all is completely vegetarian-friendly: Irish moss. Also known as carrageenan, Irish moss is used during the actual brewing process — typically a few minutes before the cold break, when the beer is quickly cooled to encourage the precipitation of proteins from the unfermented wort. Irish moss binds to these proteins and encourages a strong cold break, which means clearer wort going into the fermenter.
While Irish moss is effective at precipitating proteins from cooling wort, it does nothing to clean up the mess left by the fermentation process. Gravity, temperature and time can also be used to remedy this. Have you ever seen a fermenter in a brewery? Its conical shape is designed to allow yeast and proteins to settle out at the bottom, where it can then be removed from the rest of the beer.
This process is usually facilitated by a process called cold conditioning, where the temperature of the beer is dropped to near-freezing for a few days, which causes large particles to drop out of suspension. Other breweries go an extra step, running the finished beer through a large centrifuge, which effectively separates larger particles from the clear liquid.
While fining agents — animal-based ones included — are in no way harmful to drinkers, vegetarians and vegans will likely want to know if their favorite beers are vegetarian-friendly. Barnivore.com is the most well-known and comprehensive database of such information currently available.
Even if you're not a vegetarian or vegan, I hope you'll find this information useful. I know that I like to learn about all aspects of the brewing process, no matter how technical. If anything, this might "clear" some of the confusion that I frequently encounter when this subject comes up, and that's always a good thing.