The amount of reducing sugars in the potato are responsible for the colour formation of fried products. So if potatoes are to high in reducing sugars, they are not suitable for processing. The maximum limits differ somewhat by product (see table below).
It is also important to realize that the concentration of reducing sugars in potatoes is not at all static. Reducing sugars increase during storage, depending on the storage temperature. The lower the storage temperature, the more reducing sugars are formed.