Further activities
         
         
         
      1. Test for starch

      Heat 10 ml of apple juice to 70oC in a test tube. Allow to cool then add 2-3 drops of

      1% iodine in 10% potassium iodide solution (the type used for food tests). A blue colour

      indicates the presence of starch; brown shows that the starch is partially broken down;

      yellow indicates no starch.

         
         
      Note: some commercial apple juices contain practically no starch, whilst others

      have appreciable amounts. A few tests of different varieties will be needed.
       

         
         
         
      2. Test for pectin

      Add 1 part of juice to 1.5 parts of acidified ethanol ( 96% pure alcohol to which 1%

      concentrated hydrochloric acid has been added ). If flocculation occurs after 15 minutes,

      pectin is still present.
       
       
       
       

      3. Stability test

      The clarified juice is heated to 75oC, cooled down immediately and kept for 4-6 hours

      at 0oC in iced water or in a freezer. If no haze forms the juice is suitable for

      concentrating or bottling. If a haze forms the juice requires further enzyme treatment.
       

         
         
         
         
         
         
           
           
           
           All contain 10 cm of cloudy apple juice. Incubate the tubes
         in a water bath at 50oC for 30 minutes.  Observe the results