Saw a recipe for dried beans that called for soaking them with baking soda - why?

You don't need baking soda if you have a pressure cooker! So completely agree with the link info boulangere!

Came across this:

http://nutrition.about.com/od/askyournutritionist/f/bakingsodabvit.htm

Learned this tip from my aunt in New Orleans and swear by it. It is so that the beans don't give you gas.

Thanks for all the tips! Especially Sam1148. I should clarify that I usually add salt to the SOAKING water, not the cooking water, for the exact reason homemadecornbread states - I want the flavor IN the bean.

One school of thought is that soda is added to the soaking water and/or cooking water to release carbon dioxide gas so that it's not ingested. I've tried it and found it didn't make much difference. And as boulangere says, it's better not to salt your beans until later in the cooking process after the shell has softened, or they will take a long time to cook. On the other hand, don't wait til they're done, either - the salt needs time to get absorbed throughout the beans and not just flavor the water.

Lots of areas have 'hard' water with high lime/mineral content. The baking soda mellows that out. So, you'll see it called for by tradition in some recipes.

The Soda helps water helps penetrate the surface of the bean. It has some drawbacks including breaking down some vitamins...and mellowing the flavor TOO much...or even making mushy beans. I tend not to add it to the soaking liquid, but rather when cooking as sometimes it's the only thing that can tame a stubborn bean into softness.
Just a pinch 1/8-1/4 tsp is enough to use while cooking to soften the beans.
IMHO any more you run the risk of sucking out any flavor/texture of the beans.
PS: A pinch of baking soda is also old southern trick for iced tea as it neutralizes the tannins in strong tea making it less bitter.

It's a general practice not to salt (or add anything containing salt) beans until the shell has softened. Otherwise, it can take pretty much forever for them to soften and cook.

not that I'm likely to do this this week or anything (maybe next?) but it would be interesting to do two pots side by side to test the difference!

They cook up easier & faster. I think its because of the Carbon dioxide releasing factor that baking soda brings in.
Adding salt usually increases the cooking time, the opposite effect of adding soda. Not 100% of the science behind it, but beans added to soda also tends to induce bloating, (the urban myth that goes around in India restaurant circles, is that the bloating factor makes you feel fuller on less, hence its a standard restaurant economizing technique,!)