The Science of Bread Baking

[science_spot]

November 17th is Homemade Bread Day!  Many types of breads have been made in the home for thousands of years.  Among my favorite is the white yeast bread; it has such a different taste when you make your own!  Bread making is not the easiest thing I have done - there is alot of art mixed into the science of breadmaking.

Fresh bread generally consists of few ingredients - flour, water, yeast, sugar, salt, eggs, milk and oil.  Here is the basic white bread recipe I started with.  If you look around the internet or Cafemom's Homemade Bread Making group, you will find many other recipes.  Each ingredient contributes to the baking process and the form of the bread when it has completed baking. There are many other ingredients added to make all those unique breads out there.  Yum.  There are many types of bread, but this post is specifically about the breads that rise, such as the traditional white bread linked above.

Breadmaking isn't about just the taste.  The chemical reactions and physical change in the bread have been well-characterized for a really long time.  Understanding them may help you make better bread!  You can also use this as a science lesson with your kids, and bake some bread as part of that project. 

Breads that rise make use of a leavening agent that makes the bread rise before or during baking.  The most common leaveners are yeast, baking soda, baking powder and cream of tartar.  The last three (baking soda, baking powder, and cream of tartar) produce carbon dioxde through chemical reactions with other ingredients.  this CO2 production occurs pretty fast - which is why you stir the leavener right into the batter and bake it right away.  As the CO2 is produced during baking, it makes little bubbles of gas within the batter.  These bubbles mostly rise to the top and come right out of the batter, leaving you with a slightly raised bread, such as the banana bread my daughter likes and the zucchini bread everyone likes!

Breads that use yeast make use of a difference mechanism for rising.  Yeast in the packets is dormant until it is activated (usually with warm water).  Once activated with the water, it is ready to spring alive and feed on the sugar in the bread recipe.  This causes the yeast to produce carbon dioxide, which bubbles up in the dough, causing the dough to rise.  Punching it down will release the CO2.  After some time, it will accumulate more CO2 and rise again.  But this is a bit different from quickbreads, since the CO2 stays trapped in the dough rather than escaping out the top.  Why is that?

The answer is in the flour.  The proteins in the flour become gluten when it is mixed with water.  Kneading the dough makes the gluten form long stretchy strands which make a network of gluten fibers in the dough that trap the CO2 bubbles in there.  When the CO2 is trapped, it makes little pockets all inside the bread - this gives yeast breads the porous look we are used to, such as in the picture below, from saliusfood:

 

 

Looking for more on yeast science?  Check out Red Star Yeast - the Science of Yeast.  Looking for something a little more fun to do with bread?  Maybe Bread Art would interest you.  Or perhaps a Bread Museum is more your style.

 

Tonya

AKA sunmoonstars

The Science Spot

 

[ironkitten]

Nov. 17, 2009 at 10:24 AM

My favorite book on bread-making was a children's book I found when I was about 12 ( Let's Bake Bread! ) and was baking home made French bread as well as white bread.  Today, I am seeking out a recipe for home made whole-grain bread!  Thanks for this information.

[Lb128f]

Nov. 18, 2009 at 12:49 AM

Cool, thanks!

[aenima49]

Nov. 20, 2009 at 4:07 PM

Love it.  I get the best bread w/an instant read, digital thermometer, to make sure the liquid is neither too hot no too cool!

[science_spot]

Nov. 20, 2009 at 4:30 PM

I have been using a thermometer too, because the website said to until I am SURE I can "feel" the water correctly.

 

(Original Poster)