Hops

Question 1

What on a hop cone produces the bitter and aromatic compounds used in brewing?

Answer 1

The lupulin glands

Question 2

What are the two basic groups of hop varieties?

Answer 2

• Bittering or high α-acid varieties
• Aroma varieties

Question 3

What is the primary use of bittering or high α-acid varieties?

Answer 3

To impart characteristic bitterness to the beer.

Question 4

How does the timing of hop addition affect beer flavor?

Answer 4

Hops added at the start of wort boiling impart bitterness; hops added during fermentation provide aroma.

Question 5

What is ‘dry hopping’?

Answer 5

Adding hops during fermentation or maturation to provide aroma with little bitterness.

Question 6

What is late hop flavor or aroma?

Answer 6

Flavour resulting from hops added towards the end of wort boiling or in the whirlpool.

Question 7

What α-acid content is expected in bitter varieties?

Answer 7

Above 10%.

Question 8

What is a dual-purpose hop?

Answer 8

A hop variety that possesses both a desirable aroma and good bittering potential.

Question 9

What type of aroma can be acceptable in bitter varieties?

Answer 9

A strong, almost pungent aroma.

Question 10

What is considered a high alpha acid content? What is considered super high?

Answer 10

Super high α Super high α >15%

High α > 12%

Question 11

Which type of hop plants are cultivated?

Answer 11

Female plants

Question 12

Why must male hop plants be eradicated?

Answer 12

To prevent pollen from forming seeds in female plants

Question 13

Where are hops indigenous to?

Answer 13

Europe, Asia, and North America

Question 14

Between which latitudinal parallels can hops grow?

Answer 14

34th and 55th parallel

Question 15

In what types of regions can hops grow?

Answer 15

Cool and moist regions, dry and arid regions (with irrigation)

Question 16

When are hops harvested?

Answer 16

Hops are harvested when their moisture content is between 75-80% and their lupulin glands are filled with resins

Hops should be harvested within 10 days of ripening to prevent over-ripe cones from shattering.

Question 17

What is the first step in the hop harvesting process?

Answer 17

The hop bines are cut just above the ground and pulled off the support structure

This is followed by transportation to the harvest centre.

Question 18

What methods are used to separate leaf and stem material from the cones?

Answer 18

Fans, screens, and inclined conveyor belts are used for separation

This process ensures that only the cones are retained.

Question 19

At what temperature are hop cones dried in a hop kiln and to what moisture content?

Answer 19

Hop cones are dried at a temperature of 65°C

This process reduces cone moisture from 80% to 10%.

Question 20

What is the purpose of drying hop cones?

Answer 20

To prevent the hop cones from deteriorating

Deterioration can include changing color, developing a poor odour, or becoming mouldy.

Question 21

What is the conditioning process for hops?

Answer 21

Conditioning evens out the moisture level within the cones and throughout the batch

Hops are kept in a chamber at 20-24°C with a relative humidity of 58-65%.

Question 22

What is the consequence of not drying hop cones to 12% moisture or below?

Answer 22

The bales can combust

Proper drying and cooling are essential for safety.

Question 23

Label the hop plant

Answer 23

Question 24

What are 3 key components of hops?

Answer 24

Polyphenols, total resins and essential oils

Question 25

What are the two main subdivisions of total resins?

Answer 25

Soft resins and hard resins

Question 26

What are the main components of soft resins?

Answer 26

* α-acids * β-acids * Uncharacterised components

Question 27

What is the β-fraction in the context of soft resins?

Answer 27

Total soft resins minus the α-acids

Question 28

What are α-acids referred to as?

Answer 28

Humulones

Question 29

What are the homologs of humulones?

Answer 29

* Humulone * Cohumulone * Adhumulone

Question 30

What are β-acids referred to as?

Answer 30

Lupulones

Question 31

What are the homologs of lupulones?

Answer 31

* Lupulone * Colupulone * Adlupulone

Question 32

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

Answer 32

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

Question 33

What two methods facilitate the isomerisation of hops?

Answer 33

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

Question 34

What is the product of isomerisation of the α-acid humulone?

Answer 34

Isohumulone

Question 35

What percentage of α-acids does adhumulone typically represent?

Answer 35

10-15%

Question 36

What is the range for the levels of cohumulone and humulone in total α-acids?

Answer 36

20-50%

Question 37

Which iso-α-acid homolog has the highest solubility and utilisation?

Answer 37

Cohumulone

Question 38

Which iso-α-acids are more likely to be lost from beer due to adsorption and partitioning?

Answer 38

Isohumulone and isoadhumulone

Question 39

Which iso-α-acids are more bitter: isohumulones or isocohumulones?

Answer 39

Isohumulones

Question 40

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

Answer 40

30-35%

Question 41

What is the effect of pH on hop utilisation?

Answer 41

Hop utilisation is higher at higher pHs. A pH of 8-10 can provide 90% utilisation, while at pH 5.2, it is only around 35%. ## Footnote Boiling at higher pH is not always sensible, but some breweries do this in small vessels before the main boil.

Question 42

How does boil time affect hop utilisation?

Answer 42

The longer the wort is boiled with hops added, the greater the utilisation, up to a maximum point of around 4 hours. ## Footnote Beyond this point, additional boil time does not significantly increase utilisation.

Question 43

What is the relationship between wort gravity and hop utilisation?

Answer 43

Hop utilisation is greater in lower gravity worts because it is harder to dissolve material in more concentrated solutions. ## Footnote This relates to the general principle of solubility.

Question 44

What happens to hop acids in relation to trub?

Answer 44

Hop acids are not completely soluble in wort and can be adsorbed on trub. More trub formation leads to greater loss of hop utilisation. ## Footnote Avoiding excessive trub formation prevents low hop utilisation.

Question 45

How does temperature affect hop isomerisation?

Answer 45

The higher the temperature of the wort, the more effective the isomerisation; it drops significantly below 80°C. ## Footnote Higher temperature facilitates better extraction of hop acids.

Question 46

What happens to a-acid levels over time?

Answer 46

a-Acid levels decrease as hops are oxidised over time. ## Footnote This affects the overall hop utilisation in brewing.

Question 47

What is the effect of increasing bitterness units on hop utilisation?

Answer 47

The reduction in utilisation with increased bitterness units is largely linear until the wort is saturated. ## Footnote Higher concentration of dissolved material affects the ability to dissolve additional material.

Question 48

What factors influence hop utilisation?

Answer 48

Wort pH, concentration of dissolved material (gravity), and level of trub formation all affect hop utilisation. ## Footnote These factors must be considered when determining hop addition rates.

Question 49

What happens to iso-a-acids during boiling?

Answer 49

Iso-a-acids can be lost on any foam formed in the boil, as foam sticks to the vessel surface. ## Footnote This loss reduces the overall bitterness contributed by the hops.

Question 50

What are polyphenols also referred to as?

Answer 50

Tannins ## Footnote Tannins are a type of polyphenol.

Question 51

What percentage of polyphenols do hops contain?

Answer 51

Roughly 4% ## Footnote This percentage may fluctuate between 3-8% depending on the hop variety.

Question 52

Where are polyphenols mainly found in hops?

Answer 52

Bracts and bracteoles

Question 53

What is the source of most polyphenols found in standard beer?

Answer 53

Malt

Question 54

What percentage of polyphenols in beer comes from hops?

Answer 54

20-30%

Question 55

What do polyphenols complex with to form trub?

Answer 55

Proteins and polypeptides

Question 56

What role do polyphenols play in beer haze?

Answer 56

They may contribute to beer haze

Question 57

What are the antioxidant properties of polyphenols?

Answer 57

Act as free radical scavengers and chelate metal ions

Question 58

How do high molecular weight polyphenols affect beer?

Answer 58

Affect haze and colour

Question 59

How do polyphenols affect beer mouthfeel?

Answer 59

They affect mouthfeel and astringency

Question 60

You brew a batch of beer and add hops containing 200 grams of alpha acids. After fermentation, lab tests show 60 grams of iso-alpha acids dissolved in your finished beer. Calculate the hop utilization (%) of this brewing process

Answer 60

Step 2: Insert numbers from the question: • Iso-alpha acids in beer: 60 g • Alpha acids added: 200 g =( 60\100)*100 Final Answer: Hop Utilization = 30%

Question 61

What are some advantages and disadvantages of using T90 hops pellets

Answer 61

Advantages: • Consistent α-acid levels (standardized blends) • High extraction efficiency (27-32%+ utilization) • Reduced wort loss (less plant material) • Improved storage and handling • Traditional, no solvents • Better trub settling; easy removal in whirlpool or centrifuge Disadvantages: • Possible pesticide/fertilizer residues • Still prone to oxidation if not stored under inert gas • Better than whole hops, but still moderate utilization

Question 62

What is the utilization rate of isomerized kettle extract

Answer 62

Up to 70 percent

Question 63

What is the primary purpose of kettle hop additions?

Answer 63

Hopping primarily for bitterness - little/no hop aroma. ## Footnote Kettle hops are added during wort boiling to increase bitterness.

Question 64

What is the effect of late hop additions during the brewing process?

Answer 64

Hopping for late hop character. ## Footnote Late hop additions focus on enhancing aroma rather than bitterness.

Question 65

At what stage of brewing can isomerised extract be used to adjust bitterness?

Answer 65

During maturation after main yeast crop removal. ## Footnote This adjustment occurs after primary fermentation.