What is the difference between flour and starch?

Question

chemistry

Answer 1

Flour is made from grinding up grains, such as wheat, rice, or corn.  Starch is made when you add liquid and/or yeast to the flour like when you make bread.  The molecules of the flour and liquids or yeast stretch like a rubberband to form a starch.  You can also get lots of starch from cooked potatoes.

Answer 2

Starch is the major carbohydrate reserve in plant tubers and seed endosperm where it is found as granules [330], each typically containing several million amylopectin molecules accompanied by a much larger number of smaller amylose molecules. By far the largest source of starch is corn (maize) with other commonly used sources being wheat, potato, tapioca and rice. Amylopectin (without amylose) can be isolated from 'waxy' maize starch whereas amylose (without amylopectin) is best isolated after specifically hydrolyzing the amylopectin with pullulanase [405]. Genetic modification of starch crops has recently led to the development of starches with improved and targeted functionality [593].

Flour is what you get when you grind those seeds, or tubers up. Starch is still present, but you also have all the other things present as well.. the husk of the grain etc.  Starch is a part, flour is the whole.