Master Brewer Certification Brewer Brewing Process & Techniques 3 — Questions and Answers
Question 1: What is the purpose of adding calcium sulfate (gypsum) to brewing water?
- To raise mash pH and increase enzyme activity
- To soften water by precipitating magnesium carbonates
- To accentuate hop bitterness and dryness by lowering mash pH (Correct answer)
- To increase wort viscosity for improved head retention
Correct answer: To accentuate hop bitterness and dryness by lowering mash pH
Calcium sulfate lowers mash pH, accentuates hop dryness and bitterness, and promotes yeast flocculation and beer clarity.
Question 2: During fermentation, what is the Crabtree effect and how does it impact yeast metabolism?
- Yeast preferentially produce ethanol even in aerobic conditions when glucose concentration is high (Correct answer)
- Yeast switch to aerobic respiration when oxygen is present, maximizing biomass growth
- Yeast produce glycerol instead of ethanol at high-temperature fermentations
- Yeast cease fermentation when ethanol concentration exceeds 12% ABV
Correct answer: Yeast preferentially produce ethanol even in aerobic conditions when glucose concentration is high
The Crabtree effect causes Saccharomyces cerevisiae to produce ethanol via fermentation even in the presence of oxygen when sugar concentrations are high.
Question 3: What is the significance of the terminal gravity (FG) being higher than expected?
- Indicates successful complete attenuation and healthy yeast performance
- Suggests underattenuation, possibly from poor yeast health, low pitching rate, or a high percentage of unfermentable dextrins (Correct answer)
- Indicates excessive hop utilization that inhibited yeast activity
- Confirms that the beer has reached its target alcohol content ahead of schedule
Correct answer: Suggests underattenuation, possibly from poor yeast health, low pitching rate, or a high percentage of unfermentable dextrins
Higher-than-expected FG indicates incomplete fermentation, which may result from unhealthy yeast, insufficient pitching rate, or a mash profile that produced too many unfermentable dextrins.
Question 4: Which mash temperature range (°F) favors the production of more fermentable wort by favoring beta-amylase activity?
- 140–145°F
- 149–153°F (Correct answer)
- 158–162°F
- 168–172°F
Correct answer: 149–153°F
Beta-amylase is most active at 149–153°F, cleaving maltose units from starch chains to produce highly fermentable wort.
Question 5: What is the role of zinc in yeast nutrition during fermentation?
- Zinc acts as a cell membrane protectant against ethanol toxicity
- Zinc is a cofactor for alcohol dehydrogenase and other enzymes critical to yeast metabolism (Correct answer)
- Zinc inhibits bacterial contamination by acting as an antimicrobial agent
- Zinc promotes CO2 supersaturation for natural carbonation
Correct answer: Zinc is a cofactor for alcohol dehydrogenase and other enzymes critical to yeast metabolism
Zinc is an essential micronutrient and enzyme cofactor for yeast, particularly for alcohol dehydrogenase, and deficiency leads to sluggish fermentation.
Question 6: What does the term 'apparent attenuation' mean in brewing?
- The percentage of original gravity converted to alcohol and CO2, measured by the refractometer method
- The percentage of extract consumed by yeast, calculated from hydrometer readings of OG and FG (Correct answer)
- The reduction in hop bitterness perceived after carbonation and conditioning
- The measured decrease in dissolved oxygen during the lag phase of fermentation
Correct answer: The percentage of extract consumed by yeast, calculated from hydrometer readings of OG and FG
Apparent attenuation is the percentage of the original gravity that appears to have been fermented, calculated as ((OG-FG)/OG)×100 using hydrometer SG readings.
Question 7: What is the primary reason brewers perform a 90-minute boil for certain lager styles?
- To achieve greater hop utilization from bittering additions
- To drive off DMS (dimethyl sulfide) precursors from high-SMM lager malts (Correct answer)
- To increase wort caramelization and produce amber color in pale lagers
- To allow extended Maillard reactions that contribute to lager malt character
Correct answer: To drive off DMS (dimethyl sulfide) precursors from high-SMM lager malts
Lager malts contain higher levels of S-methylmethionine (SMM), the precursor to cooked-corn off-flavor DMS, requiring a longer boil and vigorous evaporation to volatilize it.
Master Brewer Certification Brewer Brewing Process & Techniques 3
What is the purpose of adding calcium sulfate (gypsum) to brewing water?