Chemistry canning question: While it seems you can can nearly anything, as long as it's at the right ph and processed correctly, fruit seems to play by different rules. I see on the USDA site you can can whole or cut up fruit, using very little sugar, but every preserve/compote recipe I read says to refrigerate, unless you make proper jam (mostly with the one-to-one sugar:fruit ratio or added pectin). Why is this? I have nothing against jam--I love jam--but I tend to make a slightly runnier, tarter compote at home for use in/on desserts (I don't particularly care if it gels), ice cream, cheese, etc. If it's at the right ph, why can't I can it? Any insight out there?