Sometimes when making chili, the dried beans will cook but not soften. Why is this?
In the test kitchen, we’ve found that the pH, or relative acidity, of the cooking liquid can have a dramatic effect on the rate at which beans soften (so can the age of the beans, but that’s impossible to gauge so we don’t address it in our recipes). The acidic tomatoes in something like chili may slow down softening. To speed softening when cooking dried beans in chili, wait to add tomatoes until the beans are already partially softened, and don’t add highly acidic ingredients like lemon juice and vinegar until the beans are tender.
We also recommend that you brine dried beans to tenderize the skins, which lets them soak up liquid without rupturing. Our bean-brining formula is 3 tablespoons of salt dissolved in 4 quarts of cold water for 1 pound of dried beans. Let the beans brine for 8 to 24 hours. Adding a pinch of baking soda (but no more or your beans will taste soapy) can further speed softening, reducing the cooking time by about an hour.
THE BOTTOM LINE: Acidic ingredients slow down the softening process in dried beans. When making chili, wait to add acidic ingredients (like tomatoes) until the beans have started to soften.