There is a template for librarians to use on the U drive. Use this to ensure that library staff are consistent in what is covered in the CH213L session. Here is the path: U:\Library\CH213L\Instruction template\CH213L template.docx
Taken from the CH213L lab manual fall 2017
1. Concentration of Sucrose
a. A decrease in the sucrose concentration from 6% (m/v) to 3% (m/v)
b. An increase in the sucrose concentration from 6% (m/v) to 9% (m/v)
c. An increase in the sucrose concentration from 6% (m/v) to 12% (m/v)
2. Concentration of Yeast
a. A decrease in the yeast concentration from 6% (m/v) to 3% (m/v)
b. An increase in the yeast concentration from 6% (m/v) to 9% (m/v)
c. An increase in the yeast concentration from 6% (m/v) to 12% (m/v)
3. Specific Sugar
a. Using the monosaccharide glucose instead of sucrose
b. Using the disaccharide lactose instead of sucrose
4. pH of the reaction mixture
Changing the pH to 8 instead of 5.5
Michaelis-Menten Theory - Velocity Maximum Theory - rate of reaction for enzymes is based on concentration of the substrate
Le Chatelier’s Principle - A system at equilibrium will shift to counteract the effect of a constraint applied to the system. For us in this lab, a constraint might be the concentration of a reactant or of the enzyme.
Explanation of why different sugars matter
The more complex sugars (disaccharides) must be hydrolyzed first into 2 simple sugars (monosaccharides) and then the simple sugars can undergo the fermentation reaction. The different simple sugars also ferment at different rates based on their shape/size and how easily they “fit” into the active site of the enzymes(s) in the yeast.
Note: this variable was not listed in the fall 2017 lab manual.
If students experience problems finding information on fermentation rates for regular yeast vs quick rise, encourage them to look for general information on rising time of the two types of yeast. Yeast manufacture websites provide general information on the reduced rising time of quick action or fast acting yeast. For example: http://redstaryeast.com/yeast-baking-lessons/yeast-types-usage/instant-or-fast-rising-yeast/
Or, encourage students to look up what exactly is different about quick rise yeast vs. reg yeast and think about what quick rise means in terms of gas production. Fermentation should be faster with quick rise because the gas should be released faster.
Quick-Rise yeast is a trade mark name for Red Star yeast. This type of yeast is also know as RapidRise (Fleischmann's), fast acting, or fast rising yeast.
America's Test Kitchen also has information on the different types of yeast. To find it, visit the website and enter yeast in the search box. https://www.americastestkitchen.com/
The yeast cells used in fermentation can tolerate a pH of 4.0 to 8.5 but work best when the pH is between 4.0 and 6.0. This means that yeast cells require a slightly acidic environment to do their best fermenting. More information on pH and fermentation is here: http://agriculturewithmrsskien.weebly.com/uploads/2/1/3/2/21329554/ph_and_fermentation.pdf