soaking
I have a recipe which calls for 250g of tinned black beans.. i thought i would be smart and use some DRIED black beans i have already!
but.. obviously the dried beans will weigh less than the tinned black beans..
How can i calculate how many grams of the dried beans i would need to make 250g of cooked black beans?
I was going to soak them overnight and then boil them until theyre soft!
It rather depends on the temperature of the room. Where I live, in the summer it gets hot and humid, and they shouldn't be out on the counter during the day, or they ferment. In winter (like spring in the northern US, 45-70 farenheit) they can be out for two days with no problem.
My recommendation would be to soak overnight for morning use, or to soak during the day for evening use. It also helps to change the water every few hours, though this isn't critical. If you refrigerate them with the water, you get an extra half-day. Refrigerating drained gets another day or so.
Either way, they should always be shaded, never in direct sunlight.
If they do spoil, you'll know, as they'll have a sour/yeasty smell to them.
According to this extensive bean cooking guide from University of Alaska Fairbanks, the secret is to simmer the beans gently. Unfortunately, they have little more to say on the matter.
Kenji Lopez-Alt, in his column on Food Myths at Serious Eats says (emphasis added):
Most of us have been told at some point in our culinary careers that salting beans will cause them to toughen. It's incredible that this little bit of culinary mis-wisdom still lingers, for it couldn't be further from the truth. A simple side-by-side test can prove to you conclusively that salting beans (both the water used to soak them in and the water used to cook them) actually tenderizes the skins.
It's got to do with magnesium and calcium, two ions found in the bean skins that help keep the structure of the beans' skin intact. When you soak the beans in salt water, sodium ions end up replacing some of the magnesium and calcium, effectively softening the skins. Your beans come out creamier, better seasoned, and have a much smaller likelihood of exploding while cooking.
He provides this image of the contrast:
I believe the take away from this is:
The second can easily be achieved by placing the bean pot in a moderate (350 F, 180 C) oven rather than doing it stove top.
Best Answer
250g of canned black beans is about a cup of soaked/cooked beans, which is the same as a drained 15oz/425g tin.
The volume of beans increases from 2-3x. It is probably closer to 3x for black beans but I'm not certain.
So I would cook up about 80g-90g of dry beans, I think that will get you a bit more than you need without a huge waste. 70g would probably nail it but if I'm wrong you would be short. And I'd take notes on what the weight change is for future reference :-).