I guess the technical effect justified its inclusion, but this one must rate right up there with weird and wacky processing aids! Guinness, the classic Irish stout owned by liquor giant Diageo, has used a substance called isinglass to help filter its beer for more than a century. The gelatin-like substance is removed before the beer reaches the store or tap, but trace amounts do remain.
The wacky part is that isinglass is actually made using the dried swim bladders of fish! This fact has recently led Guinness to relook at their process, as they could not claim it to be “vegetarian friendly”. Wonder if it’s anything to do with that famous creamy head?