Yes, it's the red part, the root.
I will email the site on monday and ask them your questions. just post here what you want to know, or don't understand, and I will translate and email them and get back to you here.
I found another way to ingest probiotics naturally: it's the fermented soft center of linden tree (lime tree?) sold in small vials, in boxes of 12 or 20; this part of the tree is traditionnally used in naturopathic medecine to detox the body, increase elimination, get rid of uric acid, stimulate the liver and kidneys.
So when it's also fermented, you have a two for the price of one: detox plus probiotics. Also, the problem with beet juice is that, once the bottle is opened, you have to drink it in 5 days.
With these small vials, you just drink a daily dose, and they keep nearly forever.
I have not tried it yet, but I might.