Andy M. said:Acidic ingredients added to uncooked beans will prevent the beans from softening. Your grandmother's addition of the baking soda ensured properly cooked beans. The baking soda does not help with the gas crisis.
From the site I posted above. I guess there are lots of opinions still.
There are three "facts" you'll often hear about cooking dried beans, such as kidney and great northern beans. It turns out they are all myths.
- You must soak beans before cooking. You can soak beans of course but the only advantage it provides is to shorten the cooking time. There's no reason not to start cooking dry beans directly as long as you have the time to simmer them long enough.
- You must not add salt to beans during cooking or they will not soften. Tests show that the only difference between beans cooked side by side with and without salt is that one is salty and the other is not. Some people feel that salting during cooking gives better flavor because some of the salt ends up inside the beans.
- You must not add acid, such as tomatoes, to beans during cooking or they will not soften. Acid does in fact have an effect on beans, tending to keep the skins intact, while alkaline substances (baking soda) help the skins to break down. In both cases however the beans cook perfectly well. You can use this to your advantage, adding tomatoes during or after cooking depending on whether you want whole beans or mushy beans.
Source: How to Cook Everything by Mark Bittman, Macmillan, 1998.