It is a very interesting look at the materials all around us that we just take for granted. It also looks at the future of materials science – the materials we will use to build from, and the materials we will use to repair our bodies. I highly recommend it.
I bought the book after seeing Mark’s fantastic talk at the Winchester Science Festival. Mark started his talk with a lovely story about the humble stainless steel spoon. Stainless steel is something we take for granted nowadays. And we definitely take stainless steel cutlery for granted.
Before stainless steel was invented, unless you could afford gold cutlery, our cutlery used to taste of something. Eating food with, say, a copper spoon altered how food tasted. Different spoons can make food taste more bitter or more sweet – basically, you might not be truly tasting the food if you use cutlery that tastes of something.
Not that this is always a bad thing – some cutlery may “go” well with certain food. Zinc and copper coated spoons really work well with mango, apparently . Or as the chef Heston Blumenthal said during a spoon “tasting” experiment: “the metallic note can, with some flavours, be more enjoyable than otherwise”.
So, what’s going on?
Every time you eat something with cutlery, some of the atoms from the cutlery end up in your mouth. The electrode potential of a metal gives the atoms the ability to react with the saliva in your mouth and produce ions – and these ions may taste of something. For example, saltiness is detected when taste buds encounter alkali metal ions and sourness is perceived when hydrogen ions enter taste buds.
So, depending on how many ions are produced, and which ions are produced, you won’t just be tasting your food – you’ll also be tasting your cutlery. Gold is relatively unreactive and won’t produce ions in your mouth – hence it is tasteless.
Steel is an alloy of iron and (mainly) carbon; and stainless steel has the additional ingredient of chromium. Normally, the iron in steel rusts (it oxidises). But when chromium is added to steel, it oxidises before the iron to form chromium oxide. This is transparent and coats the steel – it forms a protective layer. And it is this layer that makes the spoon tasteless. Chromium oxide is tasteless (and odourless) and so cutlery made from stainless steel is also tasteless.
As Mark puts it:
…we are one of the first generations who have not had to taste our cutlery.
So let’s stop taking the everyday materials around us for granted! Or, again, as Mark puts it:
[Whoops – just spotted Mark’s typo when he signed my copy of his book!]
Related posts and information
- Why don’t oil rigs rust?
- FT: Spoon fed: how cutlery affects your food.
- Paper by Piqueras-Fiszmana, Laughlinc, Miodownikc, Spence (PDF): Tasting spoons: Assessing how the material of a spoon affects the taste of the food.
- Stuff Matters – by Mark A. Miodownik.