How to Extract Starch From a Potato

Use baking potatoes, such as these russets, to more easily extract the starch.

Potatoes store the food the plant makes as complex carbohydrates -- also known as starches. Potato starch is useful for making homemade plastic, as a laundry-stiffening agent and to thicken recipes. Extracting the starch from potatoes is easier if you use baking potatoes, such as russets, instead of waxy red potatoes.

Things You'll Need

• Russet potato
• Knife
• Grater
• 2 bowls
• Cheesecloth
• Colander

Instructions

1. Cut the skin off of the potato and grate it into a bowl using the largest holes of a cheese grater.

2. Cover the grated potato with water and press the potato under the water.

3. Soak the potato for 30 minutes and squeeze the potato again. The water should be cloudy, indicating that the starch has leached from the potatoes.

4. Line the colander with cheesecloth and place it over the second bowl.

5. Pour the grated potatoes and water through the cheesecloth-lined colander.

6. Fold the edges of the cheesecloth over the potatoes and press to push more starchy water from the potatoes into the bowl below.

7. Use the potato starch in this liquid form or set the bowl in a sunny, well-ventilated area to evaporate the water and leave behind the powdered potato starch.

Tips & Warnings

• Harvest starch from potatoes the next time you make mashed potatoes. Save the water you use to boil starchy, russet potatoes for mashed potatoes as an alternative to grating and soaking the potatoes for starch. Strain the liquid off of the potatoes and cool it before using it in a liquid form or drying it into a powder.

References

• Practical Chemistry: Making Plastic From Potato Starch
• Science Fair Adventure: Extracting Starch Science Fair Project
• All Recipes: Making Mashed Potatoes