CSP Distillery Operations & Craft 3 — Questions and Answers
Question 1: What is the typical alcoholic strength of the wash produced after fermentation in a Scotch malt whisky distillery?
- 3–5% ABV
- 6–9% ABV (Correct answer)
- 15–20% ABV
- 25–30% ABV
Correct answer: 6–9% ABV
The wash—essentially an unhopped beer—typically reaches 6–9% ABV after yeast has consumed the fermentable sugars in the wort.
Question 2: What is 'pot ale' (also called burnt ale) and how is it typically handled?
- The first runnings from the mash tun, high in fermentable sugars
- The spent liquid remaining in the wash still after the low wines have been distilled off (Correct answer)
- The residual yeast slurry left in the washback after fermentation
- The mixture of foreshots and feints recycled into the next spirit still charge
Correct answer: The spent liquid remaining in the wash still after the low wines have been distilled off
Pot ale is the protein-rich, low-alcohol residue left in the wash still and is commonly processed into animal feed syrup or used in biogas generation.
Question 3: Which yeast strain is most commonly used in Scotch malt whisky fermentation for maximum alcohol yield?
- Champagne yeast (Saccharomyces bayanus)
- Distiller's yeast strains of Saccharomyces cerevisiae (Correct answer)
- Wild ambient yeast from the barley fields
- Brettanomyces bruxellensis
Correct answer: Distiller's yeast strains of Saccharomyces cerevisiae
Purpose-bred distiller's strains of Saccharomyces cerevisiae are selected for high alcohol tolerance, fast fermentation, and consistent yield rather than flavor complexity.
Question 4: A longer fermentation time (e.g., 72–100 hours vs. 48 hours) in Scotch whisky production generally produces what effect on the new make spirit?
- Higher phenol content due to extended bacterial activity
- Lighter, fruitier spirit with more ester development from lactic acid bacteria (Correct answer)
- Greater sulfur retention due to reduced yeast metabolism
- Higher methanol levels requiring a larger foreshots cut
Correct answer: Lighter, fruitier spirit with more ester development from lactic acid bacteria
Extended fermentation allows lactic acid bacteria to produce additional esters and acids, contributing fruity, floral notes and a lighter character to the eventual new make spirit.
Question 5: What is 'draff' and what is it typically used for after the mashing process?
- The liquid wort pumped into washbacks for fermentation
- The spent grain husks left in the mash tun, used as cattle feed (Correct answer)
- The hot water used in successive mash waters
- The CO₂ released during fermentation, captured for carbonation
Correct answer: The spent grain husks left in the mash tun, used as cattle feed
Draff is the spent, protein-rich grain residue remaining after the wort has been run off, and distilleries typically sell it as nutritious cattle feed.
Question 6: In the lauter tun or traditional mash tun, what are the three or four 'waters' (sparges) used for?
- To cool the mash at progressively lower temperatures for enzyme deactivation
- To extract sugars at progressively hotter temperatures, with later waters recycled as 'weak worts' (Correct answer)
- To separate the barley husks from the grain in successive rinse cycles
- To dilute the wort to the correct specific gravity before pitching yeast
Correct answer: To extract sugars at progressively hotter temperatures, with later waters recycled as 'weak worts'
Successive hot waters (typically 64°C, 75°C, and 85°C+) extract progressively more sugars; weak third and fourth waters are often recycled as the first water for the next mash to improve efficiency.
Question 7: Traditional Scottish washbacks are often made from Oregon pine or larch. What advantage do wooden washbacks have over stainless steel?
- Wood prevents oxygen ingress, producing a cleaner, more neutral spirit
- Resident bacteria in the wood's pores contribute to flavor complexity during extended fermentation (Correct answer)
- Wood conducts heat better, maintaining optimal fermentation temperature
- Wood is more hygienic and easier to clean between fermentation cycles
Correct answer: Resident bacteria in the wood's pores contribute to flavor complexity during extended fermentation
Wooden washbacks harbor microflora in their grain that contribute wild fermentation character and ester development, adding complexity that sterile stainless steel cannot replicate.
CSP Distillery Operations & Craft 3
What is the typical alcoholic strength of the wash produced after fermentation in a Scotch malt whisky distillery?