Four minutes. The toxins of green beans and lentils are the strongest, and it takes 4 minutes to remove the toxins, while the toxins of Dutch beans and cowpeas are low, and it takes 1 minute to remove the toxins. There are four kinds of common beans in the market: green beans, lentils, cowpeas and Dutch beans. Whether the beans are shredded or cut off, the purpose of blanching is to remove saponin and plant lectin toxic substances from raw beans.