Master Brewer Certification Brewer Quality Control & Testing 4

Question 1

What is the standard method for assessing yeast cell viability in a brewery pitching culture?

Accepted Answer

Methylene blue staining and hemocytometer counting

Answer

Methylene blue dye is excluded by living yeast cells (appearing clear) but stains dead cells blue, allowing viability percentage to be calculated using a hemocytometer.

Question 2

Which analytical test is most accurate for measuring total bitterness (iso-alpha acids) in finished beer?

Accepted Answer

HPLC (High Performance Liquid Chromatography)

Answer

HPLC directly separates and quantifies individual isohumulone compounds, providing the most precise measurement of bitterness-contributing compounds in finished beer.

Question 3

A brewery's finished beer exceeds the specification for turbidity. Which fining agent is most effective for reducing yeast and protein-related haze?

Accepted Answer

Isinglass finings

Answer

Isinglass (derived from fish swim bladders) carries a positive charge, attracting negatively charged yeast cells and flocculating them for clarification.

Question 4

What is the role of a 'wort stability test' in quality assurance?

Accepted Answer

Checking for microbial contamination in wort before yeast pitching

Answer

A wort stability test incubates a wort sample at 30°C for 24–48 hours and checks for growth or pH drop, confirming the wort is free of contamination before pitching.

Question 5

When measuring dissolved oxygen in beer using an electrochemical sensor, which condition can lead to falsely low readings?

Accepted Answer

Coating of the membrane with beer proteins or compounds

Answer

Protein fouling or hop compounds coating the sensor membrane restrict oxygen diffusion to the electrode, causing the sensor to under-read actual dissolved oxygen levels.

Master Brewer Certification Practice Test

Master Brewer Certification Practice Test

Master Brewer Certification Brewer Quality Control & Testing 4