Unit 8 - Wort Boiling Flashcards
(71 cards)
What is flavour stability in beer?
The beer’s ability to resist staling and maintain fresh flavour over time.
What causes flavour staling?
Lipid oxidation, heat damage, oxygen exposure, and metal ions like iron and copper.
How can we reduce oxidation during the boil?
- Fill kettle from the bottom to limit oxygen mixing
- Use gas sparging during fill and boil (if available)
- LOX enzyme is inactive above 67°C, so not active during boiling
What’s the 5 goals for boiling wort?
- Remove DMS
- Coagulate proteins
- Isomerise hop acids
- Sterilise wort
- Denature enzymes
Too much heat → stale flavours.
Are reductones from extra boiling helpful?
Not really—any antioxidant effect is offset by creation of staling precursors.
How do gallotannins help flavour stability?
They chelate (bind) metal ions (iron, copper) that speed up oxidation. Dose: 2–6 g per hL. Also improve haze stability.
How does trub formation help?
Trub traps lipids, removing oxidation precursors. To maximise trub:
* Keep pH around 5.2
* Encourage good boil & vapour bubbles
* Avoid excessive shear forces
* Use kettle finings or gallotannins
How do we measure if these controls work?
- EPR spectroscopy
- GC-MS (chemical analysis)
- Sensory testing over time
Enzymes are denatured below boiling temperatures. (True/False)
True and False. Most malt enzymes are denatured below boiling (e.g., α-amylase at ~80°C), but some commercial enzymes are heat-stable and require boiling to be fully denatured.
Enzymes play a crucial role in the mashing process and their stability can vary based on temperature.
Boiling destroys all microorganisms in wort. (True/False)
False. Boiling kills all vegetative bacteria and fungi, but spores may survive. Fortunately, spore-forming microbes are rarely beer spoilers.
Understanding the effectiveness of boiling is essential for ensuring the microbiological quality of the wort.
It is best to achieve the evaporation of at least 15% of the wort volume during the boil. (True/False)
False. 15% is excessive. A target of around 4% is typical in modern breweries. The goal isn’t evaporation itself, but achieving the necessary boiling reactions without wasting energy or harming flavour and foam stability.
Efficient boiling is key to preserving the quality of the beer while optimizing production.
Reactions involving amino acids and reducing sugars are the only source of flavour during the boil. (True/False)
False. Hop compounds (bitterness and aroma), adjunct sugars (like candi sugar), and mild caramelisation also contribute to boil flavour.
The complexity of flavour development during boiling is vital for creating a well-rounded beer.
DMS can form after wort boiling is complete. (True/False)
True. SMM can break down into DMS during wort clarification, and yeast can reduce DMSO to DMS during fermentation.
Monitoring DMS levels is important for the final flavor profile of the beer.
What is the optimum pH at the end of wort boiling?
Optimum pH = 5.0–5.3
Correct pH helps improve protein coagulation, diacetyl reduction during fermentation, yeast growth, faster fermentation, inhibit contaminants, reduce colour formation, and achieve correct beer pH.
Why is ensuring that the pH is correct during the boil important?
Correct pH helps:
* Improve protein coagulation
* Improve diacetyl reduction during fermentation
* Encourage yeast growth
* Enable faster fermentation
* Inhibit contaminants
* Reduce colour formation
* Achieve correct beer pH
Note: hop utilisation is not optimal in this pH range.
What is the formula to calculate percentage evaporation if the start of boil gravity is 9.7°P and end of boil gravity is 10.6°P?
Evaporation = ((10.6 – 9.7) / 10.6) × 100 = 8.5%
This is acceptable (4–10% range), but there’s room for optimisation to save energy, reduce cost and improve flavour stability.
When do kettle finings need to be optimised?
Kettle finings need to be optimised regularly and whenever process/raw materials change or wort clarity drops
Balance: wort clarity and compactness of sediment in the Imhoff cone.
What are the two parameters that need to be balanced when optimising kettle finings?
Balance:
* Wort clarity
* Compactness of sediment in the Imhoff cone
Aim = clear wort + compact sediment.
How can you improve the utilisation of T90 hops during wort boiling?
To improve utilisation:
* Increase wort pH
* Reduce trub volume
* Increase boil time or temperature
* Lower wort gravity
* Use higher α-acid hops
* Reduce foaming (fobbing)
* Increase boil vigour
Some options may compromise other quality goals.
What is the DMS level at the end of wort boiling and its potential effect on the beer?
220 μg/L is well above DMS flavour threshold (30–50 μg/L)
Beer will likely have unwanted DMS aroma.
What short-term action can you take if the wort DMS is high?
Blend with a lower-DMS brew
This is a short-term solution to mitigate the DMS aroma.
What are the long-term actions to take for future brews to manage DMS levels?
Long-term actions:
* Use malt with low SMM
* Ensure enough heat to convert SMM to DMS
* Use an efficient wort boiling system
* Minimise hot residence time after boil
* Cool wort quickly
* Consider wort stripping after clarification
These actions help reduce DMS in future brews.
What are common raw materials and process aids added during wort boiling?
Adjuncts, hops/hop products, kettle finings, gallotannins, silica sol, PVPP, antifoams, yeast food, calcium or magnesium salts, sour wort, and acids.
What role do adjuncts play when added during the wort boil?
Increase wort gravity, influence flavour, colour, and flavour stability; can dilute malt flavour, allow high-gravity brewing, and expand brew size for same malt input.
