Starch

Structure

Starch is a polysaccharide with the basic monosaccharide being Glucose. the Glucose molecules are joined together by glycosidic bonds. straight chains are made up of 1-4 glycosidic bonds while branching chain are made up of 1-6 glycosidic bonds. Starch is made up of two fractions: amylose and amylopectin. Natural starches are made up of about 20% amylose and 80% amylopectin. Amylose is soluble in hot water whereas amylopectin is insoluble. Amylose has no branching chains, but instead is made up of only 1-4 glycosidic bonds. this causes the Amylase to form a helix shape. Amylopectin however contains both straight chains and branching chains.

Testing

Starch can be tested for using Iodine solution. If starch is present then a dark blue-black colour will be seen. This dark blue-black colour is due to the Iodine reacting with the amylose helix.