Total Resins

Question 1

What are the two main subdivisions of total resins?

Answer 1

Soft resins and hard resins

Question 2

In which solvent are soft resins soluble?

Answer 2

Hexane

Question 3

In which solvent are hard resins soluble?

Answer 3

Methanol

Question 4

What components are soft resins split into?

Answer 4

α-acids, β-acids and uncharacterised components

Question 5

What is the test used to quantify the amount of each component in hops?

Answer 5

Lead conductance value of hops

Question 6

What do α-acids form when mixed with lead acetate?

Answer 6

A yellow precipitate

Question 7

What are the α-acids called?

Answer 7

Humulones

Question 8

What are the homologs of humulones?

Answer 8

• Humulone
• Cohumulone
• Adhumulone

Question 9

What are the β-acids called?

Answer 9

Lupulones

Question 10

What are the homologs of lupulones?

Answer 10

• Lupulone
• Colupulone
• Adlupulone

Question 11

Why are α-acids considered the most important constituents of hop resins?

Answer 11

They become isomerised into more soluble and bitter iso-α-acids during wort boiling

Question 12

What is isomerisation?

Answer 12

One molecule is transformed into another molecule containing exactly the same atoms, but with a different arrangement

Question 13

What are the two ways isomerisation of hops occurs?

Answer 13

• During wort boiling
• Heating α-acids with a magnesium or potassium salt in an alkaline solution

Question 14

What is the ratio of cis to trans isomers in isomerised hops?

Answer 14

Roughly 70:30

Question 15

What are diastereomers?

Answer 15

Cis and trans isomers that are not mirror images of each other

Question 16

What is the isomerised form of humulone?

Answer 16

Isohumulone

Question 17

What is the solubility characteristic of Cohumulone?

Answer 17

It has the highest solubility and utilisation due to its more polar character

Question 18

True or False: Cis-isomers are less stable than trans-isomers.

Answer 18

False

Question 19

Which iso-α-acid is more bitter: isohumulone or isocohumulone?

Answer 19

Isohumulone

Question 20

What is the typical hop utilisation percentage in beer produced using a standard brewing process?

Answer 20

Around 30-35%

Question 21

How is hop utilisation calculated?

Answer 21

% Hop Utilisation = (Mass of iso-α-acids in wort or beer / Mass of α-acids added to wort) x 100

Question 22

What pH level can provide up to 90% hop utilisation?

Answer 22

A pH of 8-10

Question 23

What effect does boil time have on hop utilisation?

Answer 23

Longer boil time increases utilisation, up to a maximum of around 4 hours

Question 24

How does wort gravity affect hop utilisation?

Answer 24

Hop utilisation is greater in lower gravity worts

Question 25

What happens to hop acids in relation to trub?

Answer 25

They can be adsorbed on trub, leading to loss of utilisation

Question 26

At what temperature does isomerisation drop significantly?

Answer 26

Below 80°C

Question 27

What is the effect of higher pressure on wort boiling?

Answer 27

It increases the boiling temperature and rate of hop utilisation

Question 28

What happens to α-acid levels as hops age?

Answer 28

They decrease as hops are oxidised over time

Question 29

Which has higher utilisation: hop cones or hop pellets?

Answer 29

Hop pellets

Question 30

How does the quantity of hops added affect utilisation?

Answer 30

More material makes it harder to dissolve additional material

Question 31

What aspect of the boiling system affects hop utilisation?

Answer 31

The vigour of the boil

Question 32

True or False: Lower α-acid hops have higher utilisation.

Answer 32

False

Question 33

What are the factors that affect hop utilisation?

Answer 33

* 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

Question 34

How can breweries increase hop bitterness while using the same total α-acids level?

Answer 34

By selecting specific hop varieties

Question 35

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%?

Answer 35

Beer brewed with Hop Variety A