Centrifuge is a most simple and convenient technique why do you need alternative method of centrifuge?if you have not centrifuge machine you can use blender to extract starch from potato.
Centrifuge just simply precipitate the starch in the solution so that you can simple separate it, in the case you have no centrifuge available, just let the suspension to stay overnight and the starch and other component will be precipitate in different rates, scratch the upper grayish layers and extract the purified starch. However, if your final aim is to predict the total starch content, use Megazym kit, in which no centrifugation is needed.