Tuesday, August 10, 2021

Potatoes to plastic: Extracting starch from potato peel

This is the first in a series of three posts which have been written by one of our advisory teachers, Jane Winter.  They are based upon our latest free resource: Potatoes to Plastic

Frequently, scientists are the bearer of bad news.  Every day we read about mounting evidence of climate change, loss of bio-diversity and the prevalence of micro-plastics in the ocean. However, did you know that as well as identifying environmental problems scientists are able to develop solutions to some of them?  The world leading Centre of Excellence in Green Chemistry where scientists work on finding new ways to overcome ecological issues is based at the University of York.

CIEC has been working with some of the scientists from Green Chemistry to develop our latest resource, Potatoes to Plastic which looks at how scientists have been able to develop useful products from a range of waste materials which might otherwise go to landfill.  As well as looking at several examples of this scientific approach to environmental problems, this free publication looks at one example, making bio-plastic from potato peel, in more depth.  Teachers are supported to carry out some straight forward activities with their class which link closely to the materials strand of the KS2 science program of study.  They extract starch from a waste product, potato peel, and then turn that starch into plastic.

Extracting starch from potato peel does not require a lot of expensive equipment. 

I have found the raw material for this activity easy to source.  Although not all chip shops peel their own potatoes, once you find one that does they will almost certainly be prepared to let you have the peel for free. Alternatively, you may find that your school dinner provider is able to give you some.  Another possibility is to use wrinkly old potatoes that have started to sprout and which might otherwise have been thrown away.

Blending the potato peel with water

First of all you will need to blend the peel and a generous quantity of water in a food processor or blender. Give each pair of children a small jug full of the mixture each.  They will need to filter the peel and water mixture by squeezing it through the foot of an old pair of tights or pop socks.  This will produce a white liquid which is a mixture of potato starch and water.  The rest of the solids are left behind and can be disposed of on a compost heap.

Pouring the blended potato peel and water into a pop sock.

After a few minutes the potato starch will start to settle at the bottom of the container.  Once this has happened the water can be poured carefully off to leave behind the wet starch.  At this point children will be amazed to find that they are left with 'oobleck' which is usually made by mixing cornstarch and water.  That is because the starch found in potatoes is exactly the same as starch found in corn.  Once children have finished playing with the oobleck it will need to be left in a shallow container such as a saucer or petri dish to dry.  After a few days all of the water will have evaporated and you will be left with dried potato starch.  

In the next post I will explain how you can turn the potato starch into plastic.  However, if you cannot wait why not check out the full instructions for both activities on the website.  This includes teachers' notes, children's activity sheets and health and safety advice.  This is what one teacher who recently carried out the activity with their class had to say about it.

'Absolutely fantastic! The children have never felt so alive, enthused and engaged in a science lesson that I have taught. They absolutely loved the practical element of blending the potatoes, filtering the starch and using interesting 'ingredients' to create the plastic. Their scientific skills were so clear and they were all extremely careful in measuring their resources and ensuring the investigation plan was carefully followed. The time taken for the excess water to evaporate and leave the powdered starch behind kept them even more engaged as they spoke about nothing for days until it was ready to use'.

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