Introduction to making bread
Chemical reactions involved when making bread
Bread making is an art of its own. The wheat grain is where everything begins. Mixing ingredients to make bread involves many chemical reactions that take place in order to give you the final product.
Bread making involves 3 stages;
- Gluten development.
- Gluten and starch break down.
- Yeast by-products.
Wheat is the grain from which flour is derived. The wheat grain consists of the bran (outer skin), the germ and the endosperm (gluten protein). Gluten (which is a type of protein) develops in flour when the flour gets hydrated with a liquid (eg; water). What we mean by this is that gluten does not exist in flour, prior to adding a liquid to the flour.
Once flour gets hydrated with water (or other liquids) and is mixed for a certain amount of time, smaller proteins (glutenin and gliadin) join together to develop a larger protein called gluten (complex protein). The higher the gluten in flour, the more water is absorbed by the flour. The dough must be mixed just enough (not too much or too little) to maximize gluten development.
The gluten amount depends on the kind of wheat (soft, hard, spring or winter) used in the flour. Wheat flour is classified by the amount of gluten protein (endosperm) it contains. Most popular flours starting from flours with the least amount of gluten, are; cake flour, pastry flour, all-purpose flour and bread flour.
How do you know that the gluten is fully developed from kneading the dough? The gluten is sufficiently developed when you can stretch a piece from the raw dough to a thin see-through layer, without breaking. Do not continue mixing dough any further or you may overdevelop the gluten resulting in inferior bread. One should stop kneading, when the raw bread dough has an internal temperature of about 85deg.C. The high-gluten flours require more mixing time to fully develop the gluten.
Gluten and starch break down
Once the gluten has developed, the gluten and the starches from the flour must be broken down into simple sugars. Some simple sugars are available in the flour, but they are not enough to give rise to the bread. The majority of the simple sugars needed by the yeast are derived from the flour’s starch molecules. The gluten (and starch) breakdown into simple sugars results from enzymes that are found in the flour and in the yeast. It is those enzymes that begin the chemical reaction, breaking down of the starches and the gluten.
Amylase is one of the enzymes that acts as a catalyst or another words causes a chemical reaction. Specifically, the chemical reaction of the amylase is to break down the flour’s starch molecules (complex carbohydrates) or proteins (gluten) into food (simple sugars such as; glucose) that the yeast can digest.
Feeding the yeast
The end result of the breakdown of the gluten and the starches is simple sugars.
While some enzymes present in the yeast, break down the starch and complex proteins of the flour into glucose molecules (simple sugar), others enzymes present in the yeast feed from the glucose molecules to produce carbon dioxide gas (CO2) and ethanol. It is the expansion of the CO2 gas that causes the bread dough to rise. When the yeast breaks down the sugars, it causes more flavor to be released from the wheat. The rising of the dough due to the carbon dioxide gaz, is called fermentation. The ethanol evaporates when the bread is baked.
An average time for the first fermentation is about 60-90 minutes. A longer fermentation period is required when the dough does not contain any milk, eggs, sugar or fat. You can slow down fermentation (retard fermentation) by placing the dough in the fridge.
That’s why if you use too much yeast in the dough, it will eat up all the sugars prematurely ending up with a bread that has an alcohol off taste.
These gases (CO2) form air pockets in the dough and expand during baking. The air pockets in the bread are large upon initial mixing, and become smaller as mixing continues. The mixing time in turn determines the texture of the bread. The dough structure around the air cells becomes hard when baked, giving a solid structure to the baked bread.
Breads that contain milk and/or sugar and/or eggs are considered enriched doughs. These type of doughs do not need long fermentation times, because the flavor comes from the fat, milk, eggs, and sugar. Also the baking temperature should be lower for enriched doughs as compared to lean doughs, like french baguette.
Enhancing the flavor of breads
In order to enhance the flavor of breads, especially lean breads (breads that contain no fat, sugar, milk, or eggs), you may use a bread ‘starter’ using yeast, called yeast starter OR a sourdough starter using wild yeast. The starter dough is simply part of the bread recipe that is made the day before, giving the yeast sufficient time to fully develop the gluten to maximize bread flavor. The starters contribute a lot of flavor due to the extended fermentation period of the dough.
Anotherwords to enhance the flavor of the bread, you need to use pre-ferments. What are pre-ferments? These are simple doughs that are prepared the day before. What do pre-ferments do? They enhance the flavor and texture of the bread, when mixed with the raw bread dough. One advantage of using pre-ferments is that the amount of yeast needed in a bread recipe is reduced.
You have two types of pre-ferments;
- Yeast starters or yeast pre-ferments
- Sourdough starters or sourdough pre-ferments
For more information on the subject, and the exact quantity of ingredients used, see our step by step video tutorials on how to make bread.
Bran - inhibits gluten development.
Dough conditioners - Dough conditioners are used to strengthen the gluten.
Fat - Fat prevents the formation of gluten development, because fat surrounds the smaller protein molecules which prevents them from getting hydrated with water, which in turn prevents gluten development.
Fruit juices - Give softness to the dough due to their acidity pH level.
Milk - inhibits gluten development.
Salt - Salt works against the yeast, by slowing down fermentation. That’s why salt and yeast should not come in contact with each other. Avoid direct contact of yeast and salt, because the salt will kill the yeast. Salt also strengthens the gluten making it more elastic. Without any salt in the dough, the gluten would be weak giving an inferior texture to the bread.
Sugar - Sugar prevents gluten development, because sugar absorbs the water that is needed to hydrate the flour.
Simple sugars - Simple sugars are converted to carbon dioxide and alcohol (ethanol) by the yeast.
Water - Amount of water used in a dough determines the hardness or softness of the bread dough. Using warm water gives the baker control of the dough temperature.
Gluten - Gives structure to bread, another words gives firmness and chewyness.
pH of water - pH level is the measure of acidity or alkalinity of water. At about room temperature the pH of pure water is about 7, where 0 is strongly acidic and 14 is strongly alkaline. For best gluten development the water should be slightly acidic (6). To alter the pH level of water you may use fruit juices to lower the pH level or make the pH level acidic or baking soda to raise the pH level or make the pH level alkali.
Water hardness - refers to the mineral content of water. High mineral content in water is referred to as hard water, while soft water refers to low mineral content. Hard water filters through deposits of calcium and magnesium-containing minerals such as limestone (Wikipedia). The harder the water the higher the pH level of water. Hard water results in a dough that is very elastic and hard to work with.
Yeast - Yeast feeds on simple sugars and produces carbon dioxide gas (CO2) which is what makes the dough rise, called fermentation. Yeast dies at 60deg. C. At this point it stops producing carbon dioxide gas.
Coagulation - refers to the hardening of the gluten when baked which gives the end result of a firm bread structure.
Crust - Crust is the exterior surface of a baked bread.
Crumb - Crumb is the interior of a baked bread.
Fermentation - When the yeast feeds on simple sugars and produces alcohol and carbon dioxide gas, which causes the rising of the dough, this is called fermentation
Hydration - The process of
Proofing – final fermentation of the bread dough.
Gluten – Gluten is the protein that develops once the flour is hydrated with a liquid.
Proofing the yeast – This is when you hydrate the yeast with a bit of water and a pinch of sugar and wait to see if it will foam up within a few minutes. If it does, the yeast is active and may be used in the recipe. If it does not foam up, it means that the yeast is no good and should be discarded.
Poorly kneaded bread will translate to a heavy and dense dough. This is because not enough carbon dioxide gas was trapped into the dough in order to form sufficient air pockets in the dough.
Over-fermented dough results in poor bread texture.