Sunday 4 August 2013

The science behind making marshmallows

Yummy Homemade marshmallows.  Super scrummy sweet and perfect in your hot chocolate, so you could always try this and then try the hot chocolate experiment or just make the marshmallows.
If you want the recipe you can go to my other blog, Fun In The Kitchen, just click the link here.
Cooking in the kitchen covers a lot of chemistry and here we are again, learning about the science of food!
Here's some of the history and science behind marshmallows...

Have you ever wondered how marshmallows are made? Long ago people made marshmallows with ingredients from the marshmallow herb. They are an ancient creation, originally coming from a tall marshmallow plant (Althaea officinalis) that grows in swampy fields and has a soft, spongy root. Its root contains mucilage, a thick, gluey substance produced by some plants and microscopic animals to help with food storage and seed germination. Some cultures used the plant to make candy, whereas others used it to make medicine. The ancient Egyptians (something we are studying at the moment) dried the root and mixed it with honey to make marshmallow treats.  However, the French experimented with using its gummy juice to soothe sore throats.
Today, shop bought and homemade ones are usually made from other ingredients like we have in the recipe in the marshmallow recipe I have on my other blog.  The main ingredients are: gelatine, golden syrup and sugar.
To make this into a really fun science experiment here's something we tried that you can try too: Explore what ratio of sugar to golden syrup produces the best-tasting and best-textured marshmallows!

Marshmallows have a melting point that is just above body temperature so that they start to change from a solid to a liquid state as soon as they reach the warmth of your mouth - or, when you're out camping, the heat of a fire!
Varying the ratio of sugar to corn syrup can significantly affect what the resultant marshmallows are like.
When you make your marshmallow look how the sugar and water solution changes as it gets nearer to 120 degrees C.   Why does it change?  Well as the sugar begins to caramelise at this temperature, the sugar compounds begin to break down and new compounds form.
What makes the meringue look so glossy?

The proteins in egg whites, especially the stronger proteins of fresh eggs, are the building blocks of meringue in the same way as they are for marshmallows. First, however, these proteins must be partially broken down through a process called denaturation, we do this to the eggs when we whisk them up.  Proteins are compressed balls of amino acid chains.  When  we whisk our eggs we break the chemical bonds that hold the chains in their tangles, allowing them to uncoil into long strands. Other chemical bonds remain, however, so the chains are still linked.   Here is a good analogy: If you think about the protein in the eggs as the unravelling of wool of a knitted jumper sleeve without undoing the whole sleeve.
Denaturation can occur physically or chemically but for a meringue, egg white proteins are denatured physically by whisking them.

Acidity also makes a difference in denaturing proteins chemically, in that fresh eggs are more acidic - that is why they work better than older ones. 
So now we have broken it down we want to build it up again, this is where we get the glossy look...

The uncoiled amino acid chains we have formed by whisking will join together (they will coagulate - if you wanted a more scientific term).  This too benefits a meringue or marshmallow in this case.
Going back to the unravelled jumper sleeve, when we add the sugar, making a meringue or the marshmallow, is like knitting a new sleeve but with a more complicated pattern by working in another type of wool.   The other type of  'wool' in this case is sugar, hot sugar with gelatine for our marshmallows.  It's mixed in to the coagulating proteins during the beating process.  Of course beating the whites also adds air to it and this air gets trapped and form tiny bubbles in a fine protein film which is what forms the foam!
Protein molecules can stretch only so far before they become weak and lose their water, this will allow the air to escape! The bubbles of air will POP in the same way as overfilled balloons. If this happens, egg white mixture will collapse in your bowl.
It is sugar that solves this problem.  When added after the egg whites start to foam when whisked, the sugar dissolves into the proteins. It bonds with them and lends them water, which increases their strength and elasticity. More bubbles form and the meringue swells—up to eight times the volume of the unbeaten whites.
It is adding the sugar that changes it's molecular structure and makes it look glossy.
I don't have a microwave (I really must get one soon though) but if you do you could try this experiment here.

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