Isinglass

Almost every page on this site ends by telling you to read the ingredient list. This is the page where that advice does not work, and it is worth having for exactly that reason.

Isinglass is collagen from the swim bladders of fish, usually sturgeon or cod. Added to a cask of beer or a tank of wine, it binds to the yeast and particles that make the liquid cloudy and drags them to the bottom, where they are left behind when the clear liquid is drawn off.

It does its job and then it is gone. That is the whole difficulty.

Why the label is silent

Because a substance removed before packaging is a processing aid, not an ingredient, and ingredient lists list ingredients.

European rules go further and name it. The Food Safety Authority of Ireland, setting out the exceptions to the fourteen allergens, lists “Fish gelatine or Isinglass used as fining agent in beer and wine” among the fish derivatives exempt from declaration.

So this is not an oversight, a loophole, or something a manufacturer is hiding. A regulator looked at it, assessed the residue as not posing an allergenic risk, and wrote the exemption down. The label is complying exactly.

For a person with a fish allergy that assessment is the reassurance. For a vegan it is beside the point, because the objection is to the use of the animal rather than to what remains in the glass.

How to find out anyway

A vegan certification mark. Certification covers processing aids, which is precisely why it is worth more than reading the list. This is the argument made at more length on the page for people avoiding animal ingredients.

Ask the brewery. Most answer readily, and many now state it unprompted because they know it is asked.

Assume nothing from the style. Real ale is the category most associated with isinglass, but plenty of cask beer is now fined with alternatives and plenty of clear industrial lager was never fined with it at all. Cloudy beer is frequently unfined, which is a genuine signal, though a deliberately hazy style tells you only that haze was wanted.

Wine is the harder case. Isinglass is one of several fining agents and the others include egg white, casein and gelatin, all animal-derived and all equally undeclared. A wine that is not certified may have been fined with any of them.

What replaced it

Bentonite, a clay. Silica gel. Pea and potato protein. Or simply time and cold, which drops the haze without adding anything.

Breweries that switched usually say so, because the number of people who care has grown enough to make it worth printing. That is the useful pattern here and it runs through several pages on this site: when avoiding something becomes commercially valuable, manufacturers start volunteering the information that the rules never required.