Presoaking

Presoaking the dried beans in water can reduce the cooking time by more than 25%.

Heat penetrates a dry seed faster than water. If cooked directly from the dry state, much of the cooking time is spent waiting for water to get to the center. Meanwhile, the outer portions of the bean overcook and become fragile. Presoaking helps by allowing the water to reach the center first, before the heat cooks them.  

Soaking times depend on temperature. It is helpful to blanch the beans for 1.5 minutes in boiling water and then allowed to soak in the cooling water for two or three hours. Blanching rapidly hydrates the seed coat that controls water movement. If soaked in cool water, it takes 10-12 hrs before beans double in size.

Salt and baking soda speed cooking. Salt concentration at 1% (10g/l or 2 tsp/qt) speeds cooking greatly. Sodium displaces magnesium from the cell wall pectins and makes them more easily dissolved. Baking soda at 0.5% (1 tsp/qt) can reduce cooking time by 75%. It also contains sodium and its alkalinity facilitates the dissolving of cell-wall hemicelluloses. These additions, however, have an effect on the taste and texture of the cooked beans. Baking soda can give a slippery mouth feel and soapy taste. Salt reduces the swelling and gelation of starch granules within the beans, so the texture is mealy instead of creamy.