Best way to rehydrate dry black beans so the skins are not hard but beans are soft?

Question

I have a recipe for rehydrating red beans that says you should boil them briefly (2 min) then soak them overnight (6-8 hrs) to rehydrate them so that the skins aren't hard.

Is this advisable? Is there a better option? Does it make any difference?

Answer

If you soak your beans in brine (3tbsp table salt per gallon of water, or 1.5% salt by weight) it'll help soften the skins by replacing calcium and magnesium ions in the skin. After soaking for 8–24 hours, drain and rinse. (Source: Cooks Illustrated, login required). Harold McGee in On Food and Cooking also mentions this (p. 488–489) and suggests 1% salt by weight. McGee also mentions that 0.5% baking soda will further reduce cooking times (but may lead to unpleasant taste & mouth feel).

Alternatively, Cook's Illustrated also reports that dried kombu can be used to similar effect, without needing the soak.

Even after brining, taste them when nearly done cooking: you may need to add some salt—it doesn't always penetrate that far into the beans. At least, that's been my experience.

Quick summary:

1. Create 1–1.5% salt (by weight) brine, approx 3tbsp table salt per gallon of water.
2. Sort (remove rocks, deformed and damaged beans, etc.) and rinse dried beans. Drain rinse water.
3. Soak rinsed beans in brine for 8–24 hours. Beans will noticeably swell.
4. Drain brine, rinse beans again.
5. Cook beans normally. Towards the end of cooking, season to taste.

You want to season towards the end of the cooking because it results in creamier texture and also eating some beans which haven't been heated to boiling for 10 minutes is ill-advised due to phytohaemagglutinin.

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