It's funny, when you look back in history books or American cookery books, one of the reasons that the quinces and cranberries are used so often is because of their natural jelling properties.
Alton BrownEnough people have now mentioned Bill Nye the Science Guy to me that I now desperately avoid it all costs.
Alton BrownCranberries contain a massive amount of natural pectins. They will gel all on their own, which is why you can basically make cranberry sauce out of filling.
Alton Brown