Master Brewer Certification Brewer Quality Control & Testing 2 — Questions and Answers
Question 1: Which method is most appropriate for detecting wild yeast contamination in a commercial brewery?
- Lysine medium plating (Correct answer)
- Standard plate count agar
- Wort agar incubation
- MRS broth cultivation
Correct answer: Lysine medium plating
Lysine medium inhibits Saccharomyces cerevisiae but supports wild yeast growth, making it selective for detecting wild yeast contaminants.
Question 2: A brewer notices haze formation in a filtered bright beer that was initially clear. What is the most likely cause?
- Protein-polyphenol chill haze development (Correct answer)
- Yeast autolysis byproducts
- Excess CO2 dissolved in solution
- Iron pickup from transfer lines
Correct answer: Protein-polyphenol chill haze development
Protein-polyphenol complexes form chill haze when beer is cold, appearing as haze that may be reversible or permanent depending on the degree of bonding.
Question 3: What does a Forced Fermentation Test (FFT) allow a brewer to determine?
- Terminal gravity a wort will achieve when fully fermented (Correct answer)
- Yeast cell viability at pitch
- The rate of alpha acid isomerization during boiling
- CO2 volumes at serving temperature
Correct answer: Terminal gravity a wort will achieve when fully fermented
An FFT uses excess yeast under warm conditions to rapidly ferment a wort sample to its terminal gravity, predicting the final attenuation before the main batch is complete.
Question 4: Which unit is used to express the bitterness level of a finished beer?
- IBU (International Bitterness Units) (Correct answer)
- EBC (European Brewery Convention units)
- SRM (Standard Reference Method units)
- BU:GU ratio
Correct answer: IBU (International Bitterness Units)
IBU (International Bitterness Units) measures the concentration of isohumulones in beer in parts per million (mg/L), representing perceived bitterness.
Question 5: What is the purpose of a beer flavor stability test using Electron Spin Resonance (ESR)?
- Measuring free radical levels to predict oxidative staling shelf life (Correct answer)
- Detecting lactic acid bacteria activity
- Quantifying dissolved oxygen at packaging
- Assessing diacetyl reduction rate
Correct answer: Measuring free radical levels to predict oxidative staling shelf life
ESR measures free radical concentration in beer, providing an early predictor of oxidative staling potential and estimated flavor shelf life.
Question 6: A beer tests at 2.4 volumes of CO2 but target is 2.6. At what stage should the brewer intervene?
- During conditioning/carbonation before packaging (Correct answer)
- At the bright beer tank before filtration
- Immediately after primary fermentation
- After packaging into sealed containers
Correct answer: During conditioning/carbonation before packaging
Carbonation adjustments must be made during conditioning or in the bright beer tank before sealing, as post-packaging CO2 adjustments are impractical.
Question 7: Which test specifically measures a beer's resistance to microbial spoilage during shelf life?
- Membrane filtration followed by LCSM incubation (Correct answer)
- Titration with sodium hydroxide solution
- Refractometer reading at 20°C
- Turbidimetric measurement at 850nm
Correct answer: Membrane filtration followed by LCSM incubation
Membrane filtration concentrates any microbes present and LCSM (Low Carbon Source Medium) incubation reveals slow-growing spoilage organisms that standard media may miss.
Master Brewer Certification Brewer Quality Control & Testing 2
Which method is most appropriate for detecting wild yeast contamination in a commercial brewery?