Juice from berries turn "jelly"

[rug]

Hi

I tried to make a delicious raspberry liquer the other day.

I squeezed juice from the berries and added strong alcohol to mix to around 40% alcohol.

An instant reaction happened....a "jelly" or "snotty" substance appeared. Approximately 50% of the volume in the bottle was nice and drinkable. The other 50% was very unpleasant to drink. It tasted good, but the "mouth feeling" was bad.

Why does this happen? And how to avoid it?