Master Brewer Certification Brewer Quality Control & Testing 3

Question 1

Which dissolved gas measurement is most critical to monitor immediately before beer packaging to prevent staling?

Accepted Answer

Dissolved oxygen (DO)

Answer

Dissolved oxygen measured in ppb (parts per billion) before packaging is critical because oxygen uptake at this stage causes oxidative staling, the leading cause of off-flavor development.

Question 2

What is the acceptable range for pH in a typical American lager wort before pitching yeast?

Accepted Answer

5.2–5.4

Answer

A mash and wort pH of 5.2–5.4 optimizes enzyme activity during mashing and supports healthy yeast metabolism and hop utilization.

Question 3

A QC technician detects elevated levels of acetaldehyde in packaged beer. What does this most likely indicate?

Accepted Answer

Premature packaging before yeast completed fermentation

Answer

Acetaldehyde, which smells like green apples, is a fermentation intermediate normally reabsorbed by yeast — elevated levels indicate yeast were removed before conditioning was complete.

Question 4

What analytical instrument is commonly used for routine measurement of ethanol content in finished beer?

Accepted Answer

Anton Paar density meter or distillation-based ebulliometer

Answer

Anton Paar oscillating U-tube density meters provide rapid, accurate ABV calculation, while ebulliometers use boiling point differential — both are common brewery QC tools.

Question 5

During sensory evaluation of a beer, a panel identifies a 'cooked corn' or 'creamed corn' off-flavor. Which compound is responsible?

Accepted Answer

Dimethyl sulfide (DMS)

Answer

DMS (dimethyl sulfide) produces a cooked corn or vegetable aroma in beer, typically from inadequate wort boiling or slow chilling that allows S-methyl methionine (SMM) to convert.

Master Brewer Certification Practice Test

Master Brewer Certification Practice Test

Master Brewer Certification Brewer Quality Control & Testing 3