Bread
In the cold of winter, bread with its complex chemistry, is at once a daily staple, holiday treat, and a symbol of life itself.
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On Dec. 13th, Scandinavians celebrate St. Lucia’s Day with a procession in the community led by a young girl wearing a white gown, red sash, and crown of candles giving out warm saffron buns decorated with raisins. In the cold and dark of winter, it’s no surprise that bread, a daily food staple commonly that many cultures associate with deep, symbolic meanings of life, figures prominently. In fact, the Arabic word for bread, Aish, also means life, and in Jewish tradition, challah bread is served for the weekly Sabbath and on holidays.
All breads have some common elements. The primary ingredient is flour, which can be made from a variety of different grains. Wheat is the most gluten-rich of the cereal grains and produces bread that is elastic and spongy, so wheat flour is frequently used either alone or in combination with other grains such as oat, rye, or corn for most breads. Typically, bread dough is made with a liquid, such as milk or water, often melted butter or olive oil to make the dough supple, and sweetmeats such as raisins or dried fruits are favorite ingredients for holiday breads.
Although there are exceptions, such as Jewish matzah and Indian chapati, most breads have some kind of leavening agent that produces gas bubbles and makes the dough rise. Chemical leavening agents such as baking powder can be added either as an individual ingredient or as a component in self-rising flour. The combination of baking soda with an acidic ingredient such as buttermilk, lemon, or molasses also produces the needed gas bubbles. Breads made with chemical leavening agents are known as quick breads or soda breads, and they include muffins and sweet breads, and the leavening takes place within minutes.
For most breads, however, the leavening is provided by yeast, which feasts on the flour and any sugar in the mixture to produce carbon dioxide through fermentation. Yeast-raised breads take a longer time to develop the tender crumb and flavor people prefer, up to 1 to 2 hours total, in fresh bread. The longer the rising time, the more flavor; so bakers will often “punch down” the dough and let it rise again before shaping the dough into loaves and baking.
The sour taste of sourdough breads actually comes from lactobacillus bacteria that coexist with natural yeast. When the lactobacillus feed upon the fermentation products, they produce lactic acid, which provides a tart taste and retards spoilage. Baker’s yeast, favored by many American bakers, does not include the lactobacillus bacteria, and so has a sweeter flavor. Sourdough bread is propagated through the use of a starter, which contains the active yeast and must be fed regularly with flour and water. When a new batch of sourdough bread is made, a small amount of dough is set aside to provide starter for the next batch, and through this process, starters may be sustained through multiple human generations. By contrast, pre-packaged yeast allows the flexibility to bake whenever it is convenient whether or not the starter is ready, but it lacks some of the character of bread baked with yeast nurtured over years.
More information about bread may be found at http://www.chemistrydaily.com/chemistry/Bread