User:Stellertony/Backup1

Introduction

The purpose of this experiment is to discover the effect of temperature upon the rising of bread dough. The process of dough rising is based on yeast. Yeast is a type of fungus which breaks sugar down into smaller components. The type of yeast we will be using is Saccharomyces cerevisiae, which was domesticated for wine, beer and bread production thousands of years ago. S. cerevisiae is commonly referred to as baker’s yeast or brewer’s yeast for this reason. Yeasts used for leavening bread can be either caught from the environment or produced commercially. When mixed with bread dough, the yeast converts sugar molecules into carbon dioxide (CO2), alcohol and water. The CO2 expands in the dough to produce gaseous bubbles. These bubbles cause the bread to rise - the more CO2 present, the faster the bread will rise. If temperature is related to the amount of CO2 produced by yeast, then higher temperatures will result in increased production of CO2.

Procedure

Materials:

• 1 Erlenmeyer Flask
• 1 One-hole Rubber Stopper
• 1 Bunsen Burner
• 1 Striker
• 1 Glass Beaker (any size)
• 1 Jar large enough to hold flask
• 1 Thermometer
• Yeast Solution
• Ice
• Hot Plates
• Glass Tubing
• Access to tap water and natural gas will also be necessary..

1. Using the bunsen burner, bend the glass tubing so that it will reach from the inside of the Erlenymeyer flask to the bottom of the glass beaker, leaving enough room for gas to escape while in the beaker. (See Figure 1)

2. Add 75 ml of yeast solution to the flask.

3. Add 500 ml of water to the beaker.

4. Place the rubber stopper in the flask and insert the glass tubing so that it will receive gas from the flask and carry it underneath the water in the beaker. Place the beaker and flask on a lab counter. (See Fig. 1)

5. Observe the beaker for ten minutes and count the number of bubbles escaping into the water. Record this information and the current room temperature in a data table. (See Fig. 2)

6. Find the average number of bubbles per minute and record this in the data table.

7. Remove the glass tubing from the apparatus.

8. Repeat steps 2-7 at a temperature of ___ degrees Celsius, placing the flask in a hot water bath and ensuring that the yeast solution has reached the appropriate temperature before inserting the glass tubing. (See fig. 3)

9. Repeat steps 2-7 at a temperature of 0 degrees Celsius, placing the flask in a cold water bath and ensuring that the yeast solution has reached the appropriate temperature before inserting the glass tubing. (See fig. 4)

10. Disconnect the materials, clean them and replace them in their proper locations.