The chemistry of bread
While baking bread may appear to be a very simple process, there is actually a lot of science in how the four basic ingredients interact. Also, some of the terminology used when trying to describe how bread is made be a little confusing. In this blog, we hope to explain things a little more clearly and help you understand what’s going on at a molecular level!
First of all, if no sugar is added to our bread, then where does the sugar come from for fermentation? Enzymes that are naturally present in the four (and the additional enzymes that might also be added to speed things along) feed on the starch in the flour and convert it into sugar. These enzymes are called amylases.
Bread needs a rising or “leavening” agent. While some breads and cakes use baking soda to produce the gas for this, in our breads, yeast is used to ferment the sugar that has been released during fermentation. In doing so it releases carbon dioxide gas which is what makes the bread rise, and the sugar is converted into alcohol, contributing to the flavour. The alcohol evaporates off completely during baking of course, so there is nothing to worry about! Sourdough bread uses a mixture of wild yeasts and bacteria from the environment.
What is gluten? Flour contains high levels of glutenin and gliadin proteins which together are called gluten. Gluten is a general name for the proteins found in wheat, spelt, semolina, rye, barley and other grains. Gluten helps foods maintain their shape, acting as a glue that holds food together: When water is added, these proteins form a network held together by hydrogen bonds & disulfide cross-links. Kneading uncoils gluten proteins, strengthening the network and the dough. It sounds chemical, and it is, naturally!
And finally, why does the crust of bread go brown during baking? When dry heat is applied, as in baking, the heat causes the starch to break down by chemical reaction into sugars called dextrins. The dextrins are brown in colour and have their own unique texture and taste. This process is called “dextrinization”. However, if too much dry heat is applied, overcooking turns the starch into carbon instead, which is black.
We hope you’ve enjoyed reading this and hope you’ve learned something new from our little bit of chemistry!
For more information, check out these great resources:
· Coeliac Society of Ireland https://coeliac.ie/
· “Bread Science: the Chemistry and Craft of Making Bread” by Emily Buehler, published by TwoBlueBooks – this is really clearly written and easy to read;
· Compound Chem – The Aroma of Freshly Baked Bread: https://www.compoundchem.com/2016/01/20/bread-aroma/
· Compound Chem - Baking Bread: The Chemistry of Bread-Making has a great infographic:: https://www.compoundchem.com/2016/01/13/bread
· Love Food Science: https://www.ifst.org/lovefoodlovescience/resources?keyword=bread