My wife does lots of canning and freezing ever year - lots of it comes from our garden and we also get a lot of free fruit from friends and relatives. All the stuff she cans and freezes is organically grow so I think its extra good. Cheers!
I grew my own silverbeet for a while (sweeter than spinach). I've never canned anything, closest I ever got to that was bottling my own beer and ginger beer.