Sake rice is usually polished to a much higher degree than rice that is used as food. The reason for polishing is a result of the composition and structure of the rice grain itself. The core of the rice grain is rich in starch, while the outer layers of the grain contain higher concentrations of fats, vitamins and proteins. Since higher concentration of fat and protein in the sake would lead to off-flavors and contribute rough elements to the sake, the outer layers of the sake rice grain is milled away in a polishing process, leaving only the starchy part of the grain (some sake brewers remove over 60% of the rice grain in the polishing process). That desirable pocket of starch in the center of the grain is called the shinpaku (心白, しんぱく). It usually takes two to three days to polish rice down to less than half its original size. The rice powder by-product of polishing is often used for making rice crackers, or Japanese sweets (i.e. Dango), and other food stuffs.