Milling Principles SAQ Flashcards
(12 cards)
Is it true that increasing the speed of the rollers will always increase the throughput of a roller mill?
False. While slower speeds can reduce throughput, higher speeds can cause grains to bounce, reducing throughput due to ‘riding the rollers’.
This phenomenon refers to grains not being crushed effectively because they do not reach the rollers properly.
What does compression of the grain in a roller mill primarily cause?
Fracture of the grain, which reduces particle size.
Shear helps in separating husk fragments from endosperm fragments.
Is husk integrity more important in a grist for a mash tun than for a lauter tun?
False. Husk integrity is equally important for both, but its nature may be more critical in a lauter tun due to a thinner filter bed.
The finer grist in a lauter tun requires careful consideration of husk quality.
How is the particle size produced by a hammer mill determined?
By the holes in the screens, not just the speed of the rotor.
High rotor speed can produce finer grist in specific conditions but is not the main determinant.
What is extract efficiency?
The amount of extract in the wort as a percentage of the amount of extract in the grain.
It indicates how effectively the milling process extracts sugars from the grain.
What should be checked before reducing the mill gap to optimize extract efficiency?
Wort separation performance and if it meets target time and clarity specifications.
Ensuring that wort separation is functioning well is crucial before making adjustments.
What is the purpose of checking the grist against the brewery’s specification?
To determine if it is out of specification and if further adjustments are necessary.
If the grist is already at the bottom of specification, making it finer may not be advisable.
What is shear in the context of roller milling?
Forces applied from opposite sides that help pull the grain apart.
Shear is essential for effective comminution and wort separation.
How is shear achieved in roller milling?
Through roller fluting and differential roller speeds.
Fluting increases friction and provides cutting surfaces, while differential speeds help pull the grain apart.
What are the key objectives of successful milling?
Produce required particle size distribution, maintain husk integrity, maximize extract efficiency, operate safely, achieve programmed brewhouse cycle time.
Each objective addresses specific challenges based on malt modification levels.
What is the recommended mill type for a mash tun using well-modified malt?
A four-roller mill.
It produces a coarse grist with improved extract compared to a two-roller mill.
What is the best mill for a mash filter using under-modified malt?
A hammer mill.
A six-roller mill can be used, but the hammer mill achieves greater extract due to finer comminution.
