Did I say plastic cheese? I meant cheese plastic, that is, plastic made from the cheese protein casein.
Casein comes from the Latin word caseus, which means ‘cheese’, and it’s a protein found in mammalian milk. It makes up 80% of the protein content of cow’s milk, and 20-45% of the protein in human milk.
And because it makes up most of the solid curds you get when a coagulant is introduced to acidified milk, it’s a pretty big part of cheese. Which is pretty awesome, but not everyone wants to rush out and make their own cheese.
Fortunately, casein also has some other uses that are easy to copy in your own home. As the video below demonstrates, you can separate milk into fat and protein curds and whey by adding vinegar. And when the protein is separated and dried, it sets very hard, making it a simple DIY plastic.
This casein plastic was common before the widespread use of petroleum-based plastics. A particular brand called Galalith, from the Greek for milk and stone, was used to make buttons. Casein was also used to make billiard balls and other hard moulded objects.
But its usefulness doesn’t stop there; a number of fibres have been produced by extruding the protein. These can then be made into clothing, and it is still being used for this purpose today.
It’s also used in dentistry for repairing teeth, in certain paints and in glue for specific applications, such as when its heat resistance is required (you can also make casein glue at home, by neutralising the acid before it hardens).
Structurally, the protein is very similar to gluten, so some people have allergic reactions to it, and must avoid it in their diet. Recently it has been suggested as a trigger for autism in children, but so far no evidence supports this hypothesis (Millward C, Ferriter M, Calver SJ & Connell-Jones GG, “Gluten- and casein-free diets for autistic spectrum disorder”, Cochrane Database of Systematic Reviews 2008, Issue 2. Art. No.: CD003498. DOI: 10.1002/14651858.CD003498.pub3).
We’ve pretty much milked this topic for all its worth… But here’s one more video on casein. Well, close enough.
(This story first aired on 22 August 2013 – you can listen to the podcast.)