The potent, milky-white beverage produced by fermenting cassava (Manihot esculenta) is called masato in the Peruvian Amazon. The brew is also known (to non-Amazonians) as "spit beer" because of the way that it is prepared. To stimulate the fermentation process, the cooked cassava tubers are first chewed and then spat out into a large pot. Apparently, the enzymes and bacteria in saliva give the beverage its characteristic taste. New (young) masato tastes a bit like yogurt; older masato is really, really alcoholic and strong. You are always offered a glass of masato the first time you visit a village. [NOTE: The image above, scanned from a print, was taken along the Rio Ucayali. I can't remember the name of either the village or the lady. Must have been good masato].