I ran out of organic brown rice today, and I happened to have some lentils, but when I went to rinse them with the spray nozzle on my sink (set to warm) they started to create a bubbly foam. The lentils were in a bowl not a strainer. I'm not used to this, so I'm wondering if it's natural. But I'm also recalling how when I made homemade potato chips and when I rinsed thin slices of potatoes I got a similar foaminess.
What's causing this foam? Is it natural with lentils?