Challah (Braided) Bread recipe

As posted by Dr. Patti Christie on http://ocw.mit.edu/courses/special-programs/sp-287-kitchen-chemistry-spring-2009/readings/MITSP_287s09_read05_Challah.pdf

Adapted from the Guggenheim Family, Zurich, Switzerland.

Ingredients:

• 1 package of dehydrated yeast (2 1/4 tsp).
• 1/2 cup sugar
• 2 cups of water at 115 - 120 degrees F.
• enough flour to make a dough (about 5-6 cups)
• 1 tbsp salt
• 2 tbsp oil
• 1 egg
• cooking spray
• egg yolk

Method:

• Mix together water and sugar. Make sure the temperature of the solution is between 110-115 degrees F.
• Sprinkle a package of yeast over the top and let sit for 10 minutes.
• Mix together egg, oil, and salt. Add to yeast mixture.
• Mix in the flour. The total amount of flour will be between 5-6 cups. Add 2 cups of flour and mix. Then add another 2 cups and mix well. Gradually add the rest of the flour to make a dough that is able to come off the sides of the bowl.
• Knead together until the dough is shiny and elastic.
• Spray cooking spray on bowl. Place dough into bowl and flip until covered with cooking spray.
• Cover with a piece of plastic wrap, which has been sprayed with cooking spray and also a towel. Let rise in a warm place (works best if the temperature of the dough is between 85-95 degrees F) until double in bulk. This will take about an hour.
• Carefully punch down and divide the dough into pieces to be braided.
• Braid the bread and cover with the plastic wrap and towel to let rise for about 30 minutes (half the amount of time as the first rising). 
• Mix equal parts of egg yolk and water. Brush egg yolk mixture on top of dough.
• Cook at 350 degrees F for 35-45 minutes or until it sounds hollow when tapped.

Staling

Though staling seems to involve the loss of moisture as the bread becomes dry, hard, and crumbly, it is more of an effect of starch retrogradation than net water loss. In 1852, Frenchman Jean Baptiste Boussingault conducted an experiment where bread was hermetically sealed to prevent moisture loss, yet it still became stale. Staling is now understood to be a manifestation of recrystallization and water migration out of the starch granules into the surrounding gluten network. The retrogradation of simple amylsoe molecules leads to the hardening of the bread. Branched amylopectins also retrograde, but do so more slowly. Certain emulsifying agents have been found to retard staling substantially. Manufacturers have added these to mass-produced bread dough for the last 50 years. True buttermilk and eggs have the same effects.

As long as the loaf is not too old, or has been refrigerated, staling can be reversed by reheating the bread above the gelation temperature of starch, 140 degrees F/60 degrees C. Toasting makes the interior of bread soft. A loaf of bread can be refreshed by heating in the oven.

Refrigerating bread can speed up the staling process by as much as 6 days! If bread is to be used in a couple of days, it is best to store at room temperature in a bread box or paper bag to reduce moisture loss. If bread is to be kept longer, it is best to wrap it in plastic or foil, and freeze it. Refrigerate bread only if it is to be toasted or reheated before consumption.

Bread tends to dry out before becoming spoiled. Still, bread that is kept at room temperature in a plastic bag allows moiture from the staling starch granules to collect on bread surfaces. The most commonly found toxic molds in spoiled bread are Aspergillus, Penicillium, Mucor, and Monilia sitophila.

Dough, batter, and texture

Wheat flour has characteristic liveliness and cohesiveness that set it apart from other cereal doughs. These characteristics make it possible for light, delicate loaves, flaky pastries, and silken pastas.

There are three basic elements at work: water, the flour's gluten proteins, and its starch granules. When integrated, these elements create cohesive mass.

Mixture of flour and water is called a dough or batter depending on the relative portions of the ingredients. According to Harold McGee, "doughs contain more flour than water and are stiff enough to be manipulated by hand. All the water is bound to the gluten proteins and to the surfaces of the starch granules, which are embedded in the semisolid gluten-water matrix. Batters contain more water than flour and are loose enough to pour. Much of the water is free liquid, and both gluten proteins and starch granules are dispersed in it." Once cooked, the starch granules absorb water, swell, and create a permanent sponge-like structure made up of millions of tiny air pockets.The term crumb refers to this network. Crust is the outer surface.

The texture of breads and cakes is light and tender because the protein-starch mass is divided up by millions of tiny bubbles. Pastries are flaky and tender because the protein-starch mass is interrupted by hundreds of layers of fat.

Bread 101

What qualifies as bread? On the most basic level, bread is the result from cooking a mixture of milled grains and water. Here is a quick run down of the most common ingredients in bread:

• Flour - Wheat flour is most commonly used in raised bread because it contains two proteins, glutenin and gliadin, which form gluten when combined with water. As the baker kneads the dough, the gluten develops and becomes elastic. This elasticity allows the incorporation of carbon dioxide gas into the dough.
• Starch is a carbohydrate that makes up 70% of the flour by weight. Starch granules release sugars that the yeast feed on. Starch reinforces gluten and absorbs water during baking, helping the gluten contain the carbon dioxide.  
• Water is the most important liquid in bread. It dissolves and activates yeast and blends with the flour to create gluten.  
• Yeast is a live, single-cell fungus that begins feeding on the sugars in flour and releases the carbon dioxide that makes bread rise. Yeast also adds many of the flavors and aromas associated with bread.
• Baking powder and baking soda are chemical leavenings that participate in the reactions between acidic and alkaline compounds that produce the carbon dioxide necessary to inflate dough or batter. These chemical leavenings act much faster than yeast, and are best used in quick breads.
• Salt slows rising time, which allows the flavor of the dough to develop. Salt also adds structure to the dough by strengthening the gluten, which keeps the carbon dioxide bubbles from expanding too rapidly.
• Eggs add food value, color, and flavor. They also make the crumb fine and the crust tender. Eggs add richness and protein.
• Fat in the form of butter, margarine, shortening or oil add flavor and moisture to bread. Fat slows moisture loss and helps bread stay fresh longer.
• Other liquids such as milk, buttermilk, cream or juice may be added for flavor or to enhance texture. Only add warm liquids to dry ingredients. Too cool liquids slow or stop yeast action. Too hot liquids destroy the yeast and prevent bread from rising.
• Sweetners such as sugar, brown sugar, honey, molasses, jams, and dried fruits may be used to add flavor and color to the crust.

History of bread

There is no other food as important in the history of humanity as is bread. As Harold McGee expresses in his book, On Food and Cooking, bread took the center stage of life early on as it was "a startling sign of the natural's world hidden potential for being transformed, and [man’s] own ability to shape natural materials to human desires."

Bread and bread-making lore infiltrated language and culture early on. Words such as "Lord" come from the Anglo-Saxon hlaford, which means "loaf ward" or the master who supplies food. The word "Lady" derives its meaning from “loaf kneader.” Even the word "companion" can trace its meaning to “one who shares bread.”

The development of bread in pre-historic times is thought to have come about in two ways: First, by cooking pastes of crushed grain and water to form flatbreads; and second, from setting the paste aside, allowing it to ferment, and baking it in an enclosed oven to form raised breads.

Examples of wheat flatbreads include Middle Eastern lavash, Greek pita, Indian roti and chapatti. Latin American tortilla and North American johnnycake are flatbreads made from maize.

The history of wheat bread dates to 8000 BCE. The earliest record of leaven bread comes from the Egyptians, around 4000 BCE. Yeast production, though not entirely understood, was a notable skill. By 300 BCE, it had become a specialized profession in Ancient Egypt.

The Greeks mark on bread was one of whiteness. The early Greeks developed ways to partly refine grain in a way that it produced white bread. The Romans treasured wheat bread enough that wheat was imported from Africa to satisfy the demand of the Empire.

The 17th century brought improvements in milling and in per capita income that led to a wide availability of whiter bread and the dissolution of the brown guild. The Renaissance gave birth to pastries.

In the 1800s, most bread was still baked in communal ovens. The Industrial Revolution led to bakeries, and adulterated flour with whiteners (alum) and fillers (chalk, ground animal bones). Such developments led to the decline of domestic baking.

Furthermore, some innovations came to leaving. Pearlash, a precursor to baking soda and baking powders, appeared around 1790s. Baking powder and baking soda appeared 1830-1850s. Their development increased the ability to leaven doughs that yeast could not, such as fluid cake batters and sweet cookie doughs.

Twentieth century industrialization and modernization led to a decline in the per capita consumption of bread. As incomes rose, more people had ability to eat meat, and high-fat, high-sugar pastries and cakes. Bread was no longer the staff of life. Bread making became more industrialized in that most bread was made in large central factories, not local bakeries. The result was affordable, white bread with uncharacteristic flavor.  

Europeans and North Americans began to eat more bread in the 1980s. Traditional bread making returned. Small bakeries began to produce bread with less refined grain, building flavor with long, slow fermentation, and baking small batches in brick ovens that produced small, dark loaves. The Japanese invented the home bread machine. Today, small fraction of bread is artisan. But manufacturers have started to ship partly baked and frozen loaves to supermarkets. These loaves are rebaked locally and sold while still crusty and flavorful. Currently, we are experiencing a return to flavor and texture characteristic of traditional bread.