Question

Chemical test to differentiate glucose and starch

Answer 1

Glucose and maltose are related. Glucose is a monosaccharide (one sugar unit) and maltose is a disaccharide (two sugar units) and is comprised of two glucose units. Both glucose and maltose are reducing sugars - reducing sugars meaning that they can reduce either Cu(II) or Ag(I) under certain conditions.

There are a variety of chemical tests that can be used to identify if a sugar is a reducing sugar or if it is a mono vs disaccharide. To determine if a sugar is a reducing one, Fehling’s or Tollen’s test can be used. The Barfoed test can be used to determine if the sugar is a mono or disaccharide and gives a positive result (change for blue to red, Cu2O formation). Only monosaccharides give a positive test so this could be used to distinguish glucose from maltose.

One other test that would be useful is Glucose Oxidase test, gives a brown color with glucose, no reaction with maltose.

please choose as brain list.

Answer 2

Glucose and starch are differentiated by Benedict's Test or Iodine Test.

Benedict's Test:

• Benedict's reagent is a blue colored solution. It is blue due to the presence of copper sulfate pentahydrate.
• Benedict's reagent reacts with reducing sugars like glucose to give a brick-red precipitate of Cu₂O.
• Starch on the other hand does not react with benedict's reagent.

Iodine Test:

• Iodine solution (I₂) reacts with starch to give a blue-black color.
• The color appears due to the helical structure of starch.
• Glucose does not react with iodine solution due to the absence of a helical structure.