Starch is a polysaccharide. It is occurs widely in all plants. The main sources are wheat, maize, rice, potatoes, barley and sorghum. Starch is a white amorphous powder, insoluble in cold water. On hydrolysis with dilute acids or enzyme, starch breaks down into molecules of variable complexity and finally D-Glucose. Starch does not reduce Fehling’s solution or Tollen’s reagent. Its solution in water gives a blue colour with iodine solution. The blue colour disappears on heating and reappears on cooling.
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