A gelatinous byproduct of fish organs lurks in Guinness stout - for now
Fish bladders are used in the production process for Guinness, and have been for years.
But this week the brewery announced that it is working hard on a "complex project" to avoid reliance on a key animal byproduct called isinglass.
"We hope to have the new system up and running by late 2016 with the liquid on the shelves for consumers to buy soon after," a spokesperson from Diageo, the British company that owns Guinness, told the AFP.
Until then, traces of isinglass may be in every pint of Guinness stout.
Its role is as a "fining" to clarify an otherwise murky brew. During the brewing process, isinglass sticks to any particles and yeast cells floating in a beer, congeals into a jelly-like mass, and sinks to the bottom of the cask, so beer makers can remove it.
Taking out the congealed glob means that most isinglass is removed from the beer, but technically, Guinness has said, some isinglass likely remains in the beer. (Smithsonian Blogs has a whole history of isinglass if you want to know more.)
The use of isinglass has decreased with modern brewing methods, and not all brands of cask ales use the fishy glue to clarify their product. But there are other animal-derived, vegan- or vegetarian-unfriendly additives that can make their way into brew, including glycerol (derived from animal fat), honey (which is basically bee vomit), and lactose (derived from milk).
Barnivore.com regularly updates a giant database of vegan beers, in case you're looking to avoid any animal byproducts in your brew. We'll see if Guinness makes the list in 2016.