My bean cooking method is to soak overnight, then cook in a crockpot on low all day. By dinner time the beans are ready. I have only ever done this with a single type of bean at a time. However, I would like to make chili and I have two types of beans (white beans and red kidneys) and am wondering if this method would work if I mix the two types of beans together. Would this be generalizable to other types of beans cooking together, or more than two types of beans at a time?
Most beans can be soaked and cooked together with two exceptions.
The beans should obviously have similar cooking times. For example I wouldn't cook chickpeas with other, harder beans because the chickpeas would be mush. Most varieties do have similar cooking times so this isn't often a problem.
Second, black beans shouldn't be soaked with any other beans because they will stain the other beans a very unappealing gray color. Admittedly this is cosmetic but I soak my black beans separately
I'd like to mention possible 'gotchas' if you're going to do this --
You want to use similar-sized beans. If you're mixing small & large beans, then they're likely not going to cook at the same time.
Avoid old beans. They take longer to soften, and you don't want to find that one bean refuses to soften while the other has turned to mush.
If you're cooking red beans or any kidney bean, you need to boil the beans for a few minutes at the beginning of cooking to inactivate the phytohaemagglutinin.
So, in this particular case -- you should not just soak & throw them into a slow cooker -- as you have red kidney beans, you'd need to boil them for 10 minutes before cooking. If you were doing this on the stovetop or in a pressure cooker, you'd be fine ... but not a slow cooker.
I have a huge jar of mixed beans left over from other bags just a Hodge podge.. and I cook them all together I presoak them fast soak when I forgot.. it's got everything I can think of in there (were bean eaters lol). From chickpeas, limas, pinto, black, red and green lentils, black eyes peas, white beans red beans.. I just throw in a whole peeled onion (it disolves and gives the beans a nice sweet flavor) seasonings some sort of pork (bacon, sausage, ham hocks, left over ham bone, whatever's on hand) usually and let simmer all day. Never an issue.
I always mix beans for soups and chillies, only one type is too boring for me, never an issue. Actually, you can find bags of "15-bean soup" kits in the bean section of grocery store - they also needs to be presoaked and manufacturers dont expect you to sort everything out and soak/cook each type of bean separately :-)
It is okay. I'd suggest boiling them first, separately, to cook out the undesirable colors.
Also, if you boil the beans, let them cool, drain and cover with fresh water, boil again, repeat this until they will not boil up anymore. This removes the coloring and gassiness, at which point I combine them in the slow-cooker. also soaking before the boiling helps gas as well.