How do the Australian aborigines make poisonous foods edible?

I think alot of the food that they eat thet is 'poisonous' contains large amounts of Tanin. They wash and boil certain foods for sometimes hours or cook them underground under fires for a long amount of time. Further information: The Aborigines also knew how to make them digestible, by including all parts of the plant. For example, the Aborigines of Cooper Creek lived on nardoo, but when explorers Burke and Wills tried to eat it, they simply starved to death. This was because they did not include all parts of the plants which enables absorption of the nutrients.