Yielding Yeast, Part 2
Investigate the activation of baker's yeast and monitor the temperature and mass of the suspension.
(Photo published in Microbiol. Rev. 54: 381-431, 1990) Saccharomyces cerevisiae, baker's or brewer's yeast. Bud scars of six daughter cells are shown in blue.
Ohaus ScoutTM II Balance
(model #SR2020)
Lab Summary
Students will investigate the activation of baker's yeast through observation and by monitoring the temperature and mass of the suspension.
Yeast are simple unicellular fungi, the most familiar forms of which are brewer's yeast and baker's yeast. Both of these types of yeast are strains of the species Saccaromyces cerevisiae. Yeast cannot carry out photosynthesis but still have simple nutritional needs -- a carbon source, a nitrogen source, salts and trace elements, and the vitamin biotin. Baker's yeast is an essential ingredient for breadmaking since it causes the dough to rise: as the yeast metabolize sugar, carbon dioxide gas is produced. These gas bubbles cause the dough to rise and contribute to bread's light texture. When purchased in its dry form, yeast must first be activated by dissolving it in warm water and introducing sugar to the solution. The foam or froth that is produced and the "yeasty" aroma are signs that the yeast is actively respiring.
Hypothesize: Considering the metabolic processes of the yeast in the activated suspension, predict what will happen to the net mass of the system as activation proceeds. What other observations can you expect to make as the yeast becomes activated?
Published: April 2003
Downloads
- Yielding Yeast (15 KB, .zip)
Includes experiment setup and procedures
Here's What You Need
U.S. Educator prices shown.
Probeware (PASPORT Systems)
Xplorer GLX (PS-2002) - $349
The Xplorer GLX is a data collection, graphing, and analysis tool designed for science students and educators.
PASPORT Temperature Sensor (PS-2125) - $30
Durable stainless steel temperature sensor with a wide measurable range. For use with PASPORT Interfaces.
Other Products
OHAUS Scout Pro Balance 200g (SE-8823) - $355
Ideal for student labs and can be easily connected to DataStudio for data analysis.
Other Materials
- 50 mL of activated yeast suspension (see instructions below)
- 250-mL plastic beaker
- 100-mL graduated cylinder
- Activated yeast suspension: Dissolve 1 teaspoon table sugar (sucrose) in 200 mL warm water (approximately 40°C, or 100°F - 110°F). Add one envelope (approximately 7 grams) dry yeast (Fleishmann's® Active Dry Yeast or similar product) and mix well. This 200-mL suspension will be enough for four lab groups.
- *Note: Do not prepare this ahead of time! Prepare the suspension just before students are ready to collect data so that activation is just beginning.
