The chemistry of bread making is a rather scary title for a very simple subject, but then again bread making is for some reason somewhat shrouded in mystery. It shouldn’t be – pulling hot, golden brown, fragrant, yeasty loaves from your oven may seem like a magic trick – but there are just a few simple secrets to making the magic happen.
Actually – there are no secrets – not really. Bread baking as we know it has been around since the first enclosed oven in France in the 15th century. Four ingredients – flour, liquid, a leavener and salt – come together with two conditions – heat and moisture – and the result is bread. From this base come all the variations you can think of – foccacia, pizza dough, biscuits, cloverleaf rolls, potato bread, Irish soda bread, brioche – you name it. But they all start with the same basic elements.
Flour used in bread making is primarily all purpose or bread flour – these two contain enough of the protein called gluten to rise well. When gluten is activated by the process of kneading, it forms a structure something akin to a net. This net is what traps the carbon dioxide gas bubbles that are released by the leavener. The more dough is kneaded, and the more gluten it contains, the chewier the final texture of the bread will be.
Leaveners – which include yeast, baking soda and baking powder – are the substances which release bubbles – carbon dioxide gas. These bubbles expand and get caught in the net formed by the gluten. Yeast is a biological agent – a living microorganism. It feeds on the starches and natural sugars found in flour, and releases carbon dioxide gas as a result of this feeding process. The process, called fermentation by the way, is also what is responsible for beer. Yeasts are handy little critters! Classic French and Italian breads use all purpose flour, yeast (the leavener), water (the liquid) and salt.
Baking soda and baking powder are chemical agents. Soda is bicarbonate of soda, and will also release carbon dioxide gas when it comes into contact with acid – primarily lactic acids, which are found in dairy products. This is why Irish soda bread is made with buttermilk, as are Southern style biscuits. All purpose flour, buttermilk (the liquid) and baking soda (the leavener) make both types of bread rise. Further differences are due to methods of mixing and flavoring (the salt). Baking soda will release carbon dioxide when it comes into contact with the acid, and again when it comes into contact with the heat of the oven.
Baking powder is simply baking soda to which an acid has already been added, usually cream of tartar. Baking soda will release carbon dioxide for any moisture – and again when it gets hot. Cookies and cakes often use baking powder when there is little or no lactic acid present.
All right – we know flour has gluten, gluten traps carbon dioxide, carbon dioxide comes from leaveners – we’re three steps in! The final basic ingredient is salt. Salt is for flavoring – period. There are those who will tell you that it’s necessary for keeping the yeast from over expanding – but that’s not really true. Salt will retard the growth of yeast, and stop it entirely if there’s enough salt, but your bread dough won’t become the Giant Blob for one simple reason – and that brings us to the last two points for making bread.
The heat of an oven does three things when bread dough is added. The first thing it does is kill the yeast – yeast likes warm comfy temperatures, not the screaming heat of a baker’s oven. Heat will also ‘set’ the gluten network that formed during the kneading process. The gluten hardens, but holds on to the open spaces where the carbon dioxide bubbles were. That’s why the interior of great French bread has that lovely, holey appearance. (On a side note, those holes are great places to hold some butter or good olive oil while transporting it to your mouth.) The final thing heat does to bread is to caramelize it – giving the exterior a beautiful golden brown color and richer taste.
The last thing that comes into play for bread making is moisture. Commercial baker’s ovens often have a means by which to inject steam into the hot oven while the loaves bake – this keeps the loaves soft enough to continue their final rise, then allows that crusty, crunchy exterior to form after they’ve gotten as high as they’ll go. This can also be done at home with a spray bottle and hot pan of water. If you want a softer loaf, as for American white sandwich bread – skip the steam.
See? No secret formula, and no magic tricks. Just a little bit of science – and not even enough to put you to sleep in the back of the class. But just enough to understand the way to demystify bread making. Ready to make your own magic? Go!