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?


Yes, it's perfectly natural. Dust being rinsed off the outer surface of the lentils makes the water more viscous and helps to trap air in the form of small bubbles. In a strainer, the dust would be rinsed away, so you don't see the same effect; a spray nozzle especially adds a lot of turbulence, which causes more air to get trapped. You can get similar results when rinsing many processed, dried grains or pulses.

The effect from potatoes is similar, but it's caused by proteins in the potato being rinsed out into the soaking water. Neither has anything to do with the presence of arsenic, so don't worry.

  • 1
    I just assumed it was some unseen waxy, phospholipid bilayer-y kind of answer. They're organic, so I was curious as to why they smelled chemically. BTW, I can easily look this kind of stuff up, but I like to see what Internet people know. – user62511 Oct 29 '17 at 4:47

I've been given a jar of water from drained cooked lentils. Shake it vigorously and it will produce foam. Whisk it and I'm told it will turn stiff like the consistency of whipped cream!

  • This is not related to rinsing lentils. – rumtscho Dec 30 '18 at 22:51
  • Helen, you might want to read up on 'aquafaba'. – Joe Dec 30 '18 at 23:39

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