Total Resins Flashcards
What are the two main subdivisions of total resins?
Soft resins and hard resins
In which solvent are soft resins soluble?
Hexane
In which solvent are hard resins soluble?
Methanol
What components are soft resins split into?
α-acids, β-acids and uncharacterised components
What is the test used to quantify the amount of each component in hops?
Lead conductance value of hops
What do α-acids form when mixed with lead acetate?
A yellow precipitate
What are the α-acids called?
Humulones
What are the homologs of humulones?
- Humulone
- Cohumulone
- Adhumulone
What are the β-acids called?
Lupulones
What are the homologs of lupulones?
- Lupulone
- Colupulone
- Adlupulone
Why are α-acids considered the most important constituents of hop resins?
They become isomerised into more soluble and bitter iso-α-acids during wort boiling
What is isomerisation?
One molecule is transformed into another molecule containing exactly the same atoms, but with a different arrangement
What are the two ways isomerisation of hops occurs?
- During wort boiling
- Heating α-acids with a magnesium or potassium salt in an alkaline solution
What is the ratio of cis to trans isomers in isomerised hops?
Roughly 70:30
What are diastereomers?
Cis and trans isomers that are not mirror images of each other
What is the isomerised form of humulone?
Isohumulone
What is the solubility characteristic of Cohumulone?
It has the highest solubility and utilisation due to its more polar character
True or False: Cis-isomers are less stable than trans-isomers.
False
Which iso-α-acid is more bitter: isohumulone or isocohumulone?
Isohumulone
What is the typical hop utilisation percentage in beer produced using a standard brewing process?
Around 30-35%
How is hop utilisation calculated?
% Hop Utilisation = (Mass of iso-α-acids in wort or beer / Mass of α-acids added to wort) x 100
What pH level can provide up to 90% hop utilisation?
A pH of 8-10
What effect does boil time have on hop utilisation?
Longer boil time increases utilisation, up to a maximum of around 4 hours
How does wort gravity affect hop utilisation?
Hop utilisation is greater in lower gravity worts
What happens to hop acids in relation to trub?
They can be adsorbed on trub, leading to loss of utilisation
At what temperature does isomerisation drop significantly?
Below 80°C
What is the effect of higher pressure on wort boiling?
It increases the boiling temperature and rate of hop utilisation
What happens to α-acid levels as hops age?
They decrease as hops are oxidised over time
Which has higher utilisation: hop cones or hop pellets?
Hop pellets
How does the quantity of hops added affect utilisation?
More material makes it harder to dissolve additional material
What aspect of the boiling system affects hop utilisation?
The vigour of the boil
True or False: Lower α-acid hops have higher utilisation.
False
What are the factors that affect hop utilisation?
- pH
- Boil time
- Wort gravity
- Trub
- Temperature
- Pressure
- Hop age
- Hop product
- Quantity of hops added
- Wort boiling system
- Hop α-acid levels
- Wort composition
- Foaming
How can breweries increase hop bitterness while using the same total α-acids level?
By selecting specific hop varieties
Which beer is likely to be more bitter: one brewed with Hop Variety A or B if A has 50% Humulone and B has 35%?
Beer brewed with Hop Variety A
