Master Brewer Certification Yeast Biology & Fermentation Science

Question 1

What is the scientific name of the yeast species most commonly used in ale brewing?

Accepted Answer

Saccharomyces cerevisiae

Answer

Saccharomyces pastorianus

Answer

Brettanomyces bruxellensis

Answer

Kluyveromyces marxianus

Question 2

During which phase of the yeast growth curve does the most vigorous fermentation activity occur?

Accepted Answer

Log (exponential) phase

Answer

Lag phase

Answer

Stationary phase

Answer

Death phase

Question 3

What is the primary byproduct of yeast fermentation alongside ethanol?

Accepted Answer

Carbon dioxide

Answer

Lactic acid

Answer

Acetic acid

Answer

Hydrogen sulfide

Question 4

What is the typical optimal fermentation temperature range for lager yeast (Saccharomyces pastorianus)?

Accepted Answer

50–55°F (10–13°C)

Answer

65–70°F (18–21°C)

Answer

75–80°F (24–27°C)

Answer

35–40°F (2–4°C)

Question 5

What is the brewing term for the act of adding yeast to cooled wort to begin fermentation?

Accepted Answer

Pitching

Answer

Sparging

Answer

Mashing

Answer

Krausening

Question 6

Which yeast property describes how readily yeast cells clump together and settle out of suspension after fermentation?

Accepted Answer

Flocculation

Answer

Attenuation

Answer

Esterification

Answer

Autolysis

Question 7

What does 'apparent attenuation' measure in a fermented beer?

Accepted Answer

The percentage of original extract converted to alcohol and CO2, calculated from gravity readings

Answer

The alcohol content as measured by gas chromatography

Answer

The pH drop during fermentation

Answer

The number of viable yeast cells per milliliter