Peel the skin of the mango and cut into small pieces. Cook the mango pieces with 1cup of water. When it is done, remove from the fire and allow to cool. After that either grind it in an electric liquidiser or squeeze the mango pieces with a ladle. Sieve the solution through a cloth and keep aside.
Heat 1 1/2 kg sugar, 2 cups water and citric acid in a vessel. Stir continuously. When the sugar dissolves in the water, add the mango juice into it. When the squash boils, remove it from the fire and allow to cool. When the solution cools, take 1/4 cup of juice from it and dissolve potassium meta bisulphate in it. Pour this to the remaining squash and stir well. Store the squash in an airtight bottle.