Chemistry Freshly baked bread

Published on March 8th, 2014 | by Anna Cederlund


Homebaked science

You stand in your kitchen over-looking the counter. On this nondescript counter you have water, flour, salt and yeast. A few hours later, as if by magic and with only a little manual effort, your kitchen smells wonderful and you can open your oven to reveal a perfect loaf of bread. But how can this be? How can flour, water and yeast go from being just flour, water and yeast to a fresh loaf of bread?

In fact, baking is a lot like chemistry. The right ingredients are required in specific amounts, and they have to be added in the right order to produce the perfect loaf. A recipe can in many ways be likened to your everyday chemistry lab assignment.

Lets get baking!

Flour, the main ingredient in bread, contains two proteins — glutening and gliadin. When you add water to the flour, the two proteins are hydrated and form a complex new protein — gluten. The gluten protein forms the basic structure of most baked goods. Kneading your dough will increase the amount of structures formed, creating a complex network, and leaving the bread to rise allows the gluten threads to touch and form more structural links.

The yeast, responsible for the rising (and thereby fluffiness) of the bread is a microorganism. There are many different strains of yeast, but baker’s yeast is of the strain Saccharomyces cerevisae. When combined with dough and water, the yeast will feast on the starch in the flour, whilst exuding carbon dioxide and alcohols. These bubbles will form gas pockets inside the bread, which cause it to rise up.

Finally, in the oven the proteins form a sturdier network that traps the air bubbles, allowing the bread to come out looking and smelling just like what we expect. Scrumptious!

Just bread?

Of course it’s not just in baking bread that the chemistry matters. It plays a role in all kinds of baking, cakes, puff pastry and pies. Using different flours containing different proteins will give you very different results. The order in which you add the dry ingredients matters greatly, as they all compete for the water (using the wrong order will leave you with a clumpy batter). Mixing also plays a big role. Mixing allows the gluten threads to align, but over mixing disrupts the networks formed. Fats will tenderize your treat, they are supposed to coat the proteins instead of mixing with them, which is why you are sometimes recommended use cold butter. Eggs bind things together and baking powder serves a similar purpose to yeast, releasing carbon dioxide that forms little bubbles in the batter helping it to rise. Everything comes down to what you’re trying to produce.

And so, as I hope I’ve shown you, as it turns out, baking really isn’t that much magic. It’s just chemistry.

Featured image by jm_photos (CC BY 2.0) at Flickr.

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About the Author

Anna is a PhD student in the School of Medical Sciences. She currently is busy squishing cartilage. When not looking at videos of tiny pieces of cartilage and programming MATLAB she enjoys sunny weather, tea and editing.

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