The processing of potatoes into chuño is a technique with ancient origins. It is a complex procedure that alternates drastic hot and cold temperatures, taking advantage of the frigid waters of the rivers in the Andean plateau and the baking midday sun there. The end product is a very light, white potato (essentially dehydrated and then frozen) that resembles a piece of chalk and can last a very long time,when processed well. The presidium wants to protect this ancient method of processing and using only bitter potatoes (otherwise inedible), utilizing the best local varieties. Chuño blanco is traditionally produced in the department of Puno.