It is a common practice to blanch green beans for 3 minutes. The purpose of blanching is to soften the beans and remove the toxins in them by high temperature treatment for a short time, so as to improve the food safety. The length of blanching time can be adjusted according to personal taste. If you like the tender beans, you can slightly reduce the blanching time, and if you like the cooked beans, you can slightly extend the blanching time.