 Well, I used to make a lot of jams and stuff in a copper pot, four cups at a time. I found small batches worked well, and there was a lot of foaming with that. And also, when you boil maple sap in the spring, there's a ton of foaming going on as it reduces down. Some people say that if you chop up the fruit and macerate it overnight first, that might reduce the foaming. I've never tested that.