Some dried beans need a preliminary period of fast boiling because they contains toxins called protease inhibitors which interfere with the digestion of protein. While beans that have not had this preparation may taste palatable, the body will not benefit fully from their protein unless these toxins are neutralized.
Start by fast-boiling the beans, then discard the water and complete the cooking in a pan of fresh water. This fast-boiling is particularly important for soy beans because they contain half as much protein again as most beans and many vegetarians rely on them as a source of protein. Soy beans should be fast-boiled for 60 minutes. They should then be drained, then simmered in fresh water for another 80-90 minutes, or until tender.
Raw kidney beans contain a substance that cannot be digested and which may cause abdominal discomfort or food poisoning if the toxins are not extracted. It is essential that you fast-boil red kidney beans for 15 minutes before use, then change the water and simmer them for another 45 minutes, until they are tender.
** Asian Recipes