Cooking pulses

Why

Dried pulses have sturdy cell walls cemented with pectin, and they only soften once they have taken up water and the heat has loosened that pectin. Soaking overnight (roughly 8–12 hours) supplies the water in advance, so cooking is shorter and the beans soften more evenly; lentils and split peas don't need soaking. The old advice not to salt because salt toughens beans is a myth: sodium from salted water actually replaces some of the calcium in the pectin of the skins, which then soften and split less. What really slows softening is acid (tomatoes, vinegar, wine) and the calcium and magnesium in hard water, which firm up pectin, while pulses that have been stored for a long time soften slowly or not at all. Raw and undercooked beans, red kidney beans in particular, also contain a lectin, phytohaemagglutinin, which only a proper boil destroys; merely heating them below boiling point does not.

How to do it

• Soak beans, chickpeas and whole peas in plenty of cold water for 8–12 hours, then drain.
• Feel free to salt the soaking water; the skins will be softer and split less.
• Cover the beans with fresh water, boil them hard for at least 10 minutes, then simmer until tender, at least 30 minutes in total.
• A slow cooker won't destroy the lectin without a hard boil first, and undercooked beans can be more toxic than raw ones – always boil them first.
• Add tomatoes, vinegar or wine only once the pulses are tender.
• With very hard water, cook in filtered water or add a pinch of baking soda – no more, or they turn mushy and soapy.

If it goes wrong

Pulses that stay hard after long cooking are usually old or have met acid: lift them out of the acidic sauce and finish cooking them in water with a pinch of baking soda. Very old seeds may not soften even after hours; try a pressure cooker, blend the fully boiled pulses into a soup and buy a fresher pack next time.