What's the sourest thing in the world?

Most of us are familiar with the taste of something sour – that tart feeling that makes your eyes close and your facial features squint. Lemons, lime juice, kimchi are all sour - but what is the sourest thing in the world? We asked Janelle Clepper who has a Masters of Public Health in Nutrition from the University of Minnesota to help us figure it out.And if YOU have a question, we can help with that! Submit your Moment of Um question at BrainsOn.org/contact and we’ll help find the answer.