The formation of soy juice foam:

The seeds of plants also contain more phospholipids, such as soybeans and seeds. Phospholipids are mostly insoluble in water (foam on freshly ground soy milk is phospholipids). Homemade soymilk fast boiling when there is a lot of foam, this is the soybean contains saponins in the reason, the ingredients are toxic, will cause poisoning, but not heat-resistant, as long as the heat with a small fire to continue to boil for a few minutes, the foam will disappear. Wait until the foam disappears can be safe to drink, this time the saponins have been destroyed. Do not have to skim out, with a small fire to cook a little more will disappear.