Soup going sour after a day. What's wrong?

[PeachPapoose]

Sweet Man and I used to make these big pots of soup and they'd feed us for a few days. Then one pot went sour after a couple days and we didn't know why. We never really had a specific recipe, just dumping in lots of chopped veggies and sometimes beans, rice and/or barley. Never did bother putting any meat in as it was too expensive and the amount of other stuff thrown together was so delicious and filling it didn't beg for anything more.

So we tried again and the next batch went sour within the first day. We'd let it sit on the stovetop till it was cool enough to put in the fridge and during that wait it developed some froth and started to taste sour.

We'd tried to figure out what ingredient could have caused it. We thought maybe the peppers or the kidney beans. Not sure, though, as we'd made chili with kidney beans many a time in the past and I only had it go sour on me once (and I think that was coz I'd left it out too long before refrigerating). Wait a sec... as I'm typing I'm wondering if it could have been canned chili beans. Normally I would cook dried beans for hours but sometimes got lazy and used canned beans. Could that be it? But why would that make a difference?

Well, we kinda gave up on the big soups for awhile, discouraged. We thought it also might have been the big pot we were using, which was some light weight thing, not sure what it was made of, I'm thinking aluminum but I got it after I'd heard aluminum pots were bad for health and I figured they wouldn't sell them anymore and this one must've been something else. Not sure though.

So we finally broke down and bought a large Cuisinart stainless steel stock pot. Oh what a beauty it is! For about a month I couldn't bring myself to take it off the stove top, just had to let it sit there and gleam at us throughout the day like a piece of fine art.

We cooked a few soups in it, but when one went sour, we shied away again, sticking to using it for boring old spaghetti sauces now and then, but longing to throw together a lovingly delicious creation of multiple vegetables without fear of a sour ending.

Has anyone else ever had this happen - making a big soup and having it turn sour before it's even half gone?

I originally started making these large soups when I was coming off the Master Cleanse [the lemon juice/maple syrup/cayenne pepper cleanse]) and followed the suggestions in the book (available to read online at http://www.geocities.com/hotsprings/spa/7244/master_cleanse.html - search for "soup" and you'll see what I mean.

That's the type of soups we like, with lots of ingredients thrown in. I love cabbage soup, too, like from the "cabbage soup diet".

Maybe we need to follow a specific recipe. If so, does anyone have any suggestions?