(Mirror) - When you reach for that cold pint of beer on a hot summer's day - or a refreshing glass of wine - you might not notice there's something fishy about it.

During the beer-making process, a substance which resembles wallpaper paste is poured into the mix.

This is 'isinglass', obtained from the dried swim bladders of fish, which has been used to make beer or wine clearer since the 19th century.

Obviously, by the time it reaches our lips it's not fishy at all - but spare a thought for the beer-makers who have to put up with the smell of fish guts.

Many popular beers picked up in supermarkets have already been made vegetarian - but not all.

Watch out for Carling and Kronenbourg, which aren't veggie.

If you're drinking Stella, you're safe. But pick up a Stella Cidre and you're back to fish.

Pick up a Fosters in Australia and you're fish-free, but drink one in the UK and it's not vegetarian-friendly.