Bread Pre-Class Homework

1. What is yeast? What are the different types of yeast available?

Yeast is a single-celled fungus that has around 160 species. There are different kinds of yeast all around us in our everyday world. However, most of us are familiar with the mass-produced forms of yeast. There are four large categories of yeast used in cooking. These include Baker’s Yeast, Nutritional Yeast, Brewer’s Yeast, and Distiller’s and Wine Yeast.


2. What is the function of yeast in bread?

Yeast allows bread to rise. When bread bakes, yeast ferments the available sugars that are in the flour and added sugar. Because of this carbon dioxide gas cannot escape because the dough is elastic and stretchable. Because of this expanding gas, the dough inflates and thus rises.


3. Why do you have to add sugar to the yeast?

The fungus, which is yeast has a sweet tooth. The favorite food of yeast is sugar in the form of sucrose, fructose, glucose, or maltose. Yeast ferments the sugars that are available to create carbon dioxide gas and thus make the bread elastic and stretchable which allows it to rise. Without sugar, yeast cannot accomplish its purpose of making bread rise.


4. Why do you knead bread dough?

Site Used: http://www.wisegeek.com/why-do-you-need-to-knead-bread-dough.htm

A major important part of bread making that takes place during the kneading process gluten develops. Gluten forms as the dough is moistened and stirred and gains strength when kneading happens. Gluten is the binding agent for the dough that allows the loaf to have a cohesive texture and keeps it from falling apart. Thus, kneading also allows for the texture of bread to take form and to strengthen the bread.


5. What chemical reaction causes the elastic bread dough to form?

The chemical reaction that takes place is alcoholic fermentation. This process produces carbon dioxide and ethyl alcohol. These end products are released by the yeast cells into the liquid of the dough. When yeast ferments these sugars the carbon dioxide and other gases cannot escape and the dough becomes elastic and stretchable. Because of this expanding gas, the dough inflates and rises.


6. What is gluten? What happens if your body can't digest gluten?

Site Used: http://www.wisegeek.com/what-is-gluten.htm

Site used: http://www.mayoclinic.com/health/celiac-disease/DS00319

Gluten is a type of protein that is found in wheat, barley, and rye. It allows bread to keep its form and texture and keeps it from falling apart. It helps to make bread more elastic and provides it with a chewy texture. It is also useful in keeping the gases released during fermentation in the dough so the bread is able to rise. It also makes bread able to be absorbent so it can soap up broths.

If the body cannot digest gluten, as is the case in celiac disease, those people must avoid foods with gluten completely. If these people were to consume gluten they could end up with severe abdominal pain and diarrhea. Experts are not aware what exactly causes this disease but it results in damage to the microvillus of the intestines. This malabsorption of nutrients could also cause vitamin deficiency that could deprive the brain, nervous system, bones, liver, and other vital organs. There is no cure for this disease; however, proper diet management can yield adequate management of this disorder.


7. What is sourdough bread? What is a sourdough starter, and why is it necessary?

Sourdough bread is a type of dough that contains lactobacillus culture and is used in combination with yeasts. It is different from yeast-based breads because it produces a tangy or sour taste because of the lactic acid produced by the lactobacillus culture. A sourdough starter is a batch of bread dough that is from a previous batch of dough that has already been fermented. It is used when making a current batch of dough to give the new batch flavor. Because this dough has already fermented, it is used in subsequent dough batches for that full sourdough flavor.


8. What is responsible for the flavor, texture, and leavening differences in: injera, pita, nan, etc. (or your favorite type of bread)?





Injera:http://en.wikipedia.org/wiki/Injera
This type of bread is a yeast-risen flat bread that has a unique, spongy texture. Teff flour, made from iron-rich teff grain is used to make this bread. The teff flour is mixed with water and then allowed to ferment for many days. This is in combination with a sourdough starter. This sourdough starter gives it a mild, sour taste.


Pita: http://en.wikipedia.org/wiki/Pita

This is a very thin, pocket bread that is created by steam which puffs up the dough. When it cools and flattens, a pocket is left in the middle portion. This type of bread does not have a particular flavor and is usually always eaten with varying type of meat and hummus.


Naan: http://en.wikipedia.org/wiki/Nan_Bread

This is a type of leavened, oven-baked flatbread. It is one of the most popular Indian breads. It is cooked in a tandoor, which is a clay oven. Sometimes, baking powder is substituted for the yeast. Milk or yogurt may also be used to give naan some thickness and volume. It is usually served hot with butter or other foods stuffed inside.