A class practical on testing the presence of starch in food was performed using Foldscope by students of 6 ^th semester.

Requirements: Potato tuber, razor blade, cover slip, water, iodine solution, microscope, blotting paper, foldscope

Principle: Iodine reacts with starch and changes its colour to blue-black

Procedure:

1. Cut a thin section of a potato tube by means of razor blade or gently scrap out a few potato cells
2. Place them in a drop of water over a glass slide.
3. Observe under microscope. The cells of tuber are seen full of starch grains.
4. Pour a drop of iodine solution at one end of the mount and drain out the water from other end by means of filter paper.
5. Observe the change in colour.

Observations : The starch grains are seen to change colour to blue – black

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