It is generally recommended that one use organic whole grain flour (wheat or preferably rye) when attempting to start a sourdough culture. Using organic whole grain assures that the bran, which is covered with viable wild yeast, is present in the starting mixture. The bran also provides minerals for the yeast's growth. White flour is composed of the endosperm only (no bran) and therefore has a significantly lower concentration of indigenous wild yeast. This would make the creation of a sourdough culture starting with white flour considerably more problematic. Once the culture is viable, one can then switch over to white flour for feeding the culture.