Originally Posted by GLC
Salt does have an effect, but a subtle one. Baking soda has a stronger softening effect. Baking soda makes structures in the cell walls dissolve more readily. About one teaspoon to a quart of water. You may not like the taste. Like cilantro, some people taste it as soapy. If try this, watch the cooking time carefully. Cooking time may be as little as one quarter normal.
The opposite problem is beans getting too soft or falling apart in something that is cooked for several hours. Acids toughen those same cell walls. Sugar slows the swelling of structures that push the beans apart. Molasses is particularly good for long cooking. It has calcium, and that additional effects. And molasses is slightly acid.
Remember this when your bean recipe has something like tomatoes. Acidic tomatoes will lengthen the cooking time, and you may want to cook them a while before adding the tomatoes. Same with sugars. Partly cook the beans until they begin to soften, which means you know the cell walls are breaking down. Then add the acids and sugars. This also helps reduce the "musicality" of your beans, because they are well cooked and don't reach the lower intestines. Add epazote to bean recipes for the same reason.
Note Boston baked beans. Cooked for hours and still intact beans. Look what's in it.
And why do people often say a common bean recipe gave them hard beans? Studies show that multiple soluble compounds in beans become progressively insoluble during long storage. Dried beans are NOT completely stable. Doesn't change the nutritional value. Just makes them hard to cook. Buy smaller quantities and keep the beans rotating through the pantry before they become has-beans.
Wow!!! That's some great info, thanks!