Why do French fries sometimes go dark?
If potatoes are stored at refrigerator temperatures part of the starch in the potato changes to sugar. The high temperature needed for deep fat frying causes the sugars on the surface of the fries to darken before completely cooking on the inside. Blanching potatoes in hot water 9OoC (170oF) for several minutes removes most of the sugars and cleanses the surface of the fries to allow them to brown more evenly.