Lesson 6 - Wort Boiling Final SAQ

Question 1

What is the effect of not boiling wort on beer flavor?

Answer 1

Leads to off-flavours including DMS, diacetyl, butyric acid, and lactic acid

These flavors arise from heat-tolerant microbes metabolizing the wort.

Question 2

What is DMS and how is it related to wort boiling?

Answer 2

DMS is dimethyl sulfide, a volatile compound that should be removed during boiling to avoid a sweetcorn flavor

DMS is formed from its precursor SMM.

Question 3

What are the two forms of non-enzymatic browning during wort boiling?

Answer 3

The Maillard reaction and caramelization

Both contribute to flavor compounds in beer.

Question 4

What compounds does the Maillard reaction produce?

Answer 4

Furans, furanones, thiophenes, pyrazines

These compounds contribute flavors ranging from sweet caramel to roast coffee.

Question 5

How does boiling affect hop flavor extraction?

Answer 5

Bitterness and aroma are extracted; α-acids are isomerized into iso-α-acids

Heat is necessary for this isomerization process.

Question 6

What is the relationship between boiling and wort gravity?

Answer 6

Boiling concentrates the wort by evaporating water, raising its gravity

Higher gravity can lead to increased ester production during fermentation.

Question 7

What are the consequences of not forming and removing trub during fermentation?

Answer 7

Can lead to fermentation problems, producing off-flavors like H2S and butyric acid

Unhappy yeast can result in oversweet flavors and less crisp taste.

Question 8

What is colloidal stability in beer?

Answer 8

The likelihood of beer forming haze due to protein and polyphenol interactions

Haze forms when problematic proteins bind with polyphenols.

Question 9

What is the optimal pH for increasing trub formation?

Answer 9

Around 5.2

This pH is close to the isoelectric point of problematic proteins.

Question 10

What are kettle finings and their purpose?

Answer 10

They help precipitate proteins and polyphenols to improve colloidal stability

Examples include silica sols and gallotannins.

Question 11

What is the advantage of using an external calandria?

Answer 11

Allows for reduced boiling time and earlier wort boiling

This is due to the faster bitterness extraction and trub formation.

Question 12

What are the disadvantages of internal calandrias?

Answer 12

Difficult to clean, lower flow rate, and requires full kettle for cleaning

This can lead to high water use and effluent costs.

Question 13

What is the primary function of heat during wort boiling?

Answer 13

Inactivate malt enzymes and promote coagulation of proteins

Heat allows proteins to interact with polyphenols for removal.

Question 14

True or False: Excess thermal load can reduce foam stability.

Answer 14

True

High thermal load can lead to undesirable effects on beer quality.

Question 15

Fill in the blank: The Maillard reaction produces _______ that may help slow staling reactions.

Answer 15

reductones

Their effectiveness in slowing staling reactions is debated.

Question 16

What is the effect of very long and very hot boils on foam stability?

Answer 16

Can reduce foam stability

This occurs because they strip out proteins essential for foam stability.

Question 17

What is the purpose of using antifoam in the kettle?

Answer 17

To suppress foaming during the boil

Excess foaming can lead to weaker foam in the final beer.

Question 18

What should be regularly analyzed when making changes to the boiling process?

Answer 18

Flavour and other quality elements of the beer

This ensures that changes do not negatively affect beer quality.

Question 19

What is the effect of holding wort close to 100°C?

Answer 19

It should inactivate microbial cells effectively

This is essential for ensuring the safety of the wort.

Question 20

What should be checked to confirm successful pasteurisation of wort?

Answer 20

Activity of limit dextrinase

Limit dextrinase has a more heat-stable bound form.

Question 21

What is one method to heat wort effectively?

Answer 21

Pumping the wort through a heat exchanger

This method maintains temperature in a holding tube.

Question 22

Is a full boil necessary to kill vegetative microbial cells?

Answer 22

No, a full boil is not necessary

However, pasteurisation can be achieved through controlled heating.

Question 23

What factors are needed to calculate pasteurisation units?

Answer 23

• Wort viscosity
• Wort pH
• Wort microbial load
• Types of organism present

Question 24

What temperature range is optimal for the Maillard reaction?

Answer 24

140-160°C

This reaction contributes to flavour and colour development.

Question 25

What is a consequence of not actively heating wort?

Answer 25

The Maillard reaction will be slower ## Footnote Thermal energy drives the reaction.

Question 26

What is a recommended method to achieve similar colour and flavour to a full boil?

Answer 26

Holding the wort just below boiling for an extended period ## Footnote Alternatively, increase reactants and use a slightly increased period at raised temperature.

Question 27

What is required for caramelisation to occur?

Answer 27

Temperatures above 100°C ## Footnote Caramelisation likely won't occur in a sensible timeframe below this temperature.

Question 28

What are commercial options for adding colours or flavours?

Answer 28

Commercially produced colourings and flavourings ## Footnote These can supplement what is not formed at lower temperatures.

Question 29

What is necessary for hop aroma and flavour compounds to dissolve?

Answer 29

Sufficient agitation during the heating process ## Footnote This ensures extraction from hop products.

Question 30

What is required for isomerisation of hop compounds?

Answer 30

Heating above boiling temperature ## Footnote Pre-isomerised hop products can be used instead.

Question 31

What is needed to achieve protein coagulation in wort?

Answer 31

Holding wort close to 100°C while agitating ## Footnote Sparging with gas or steam can also help.

Question 32

What aids can be used to remove proteins and polyphenols?

Answer 32

* Gallotannins/silica sols for proteins * PVPP for polyphenols

Question 33

How can unwanted volatile flavour compounds be removed from wort?

Answer 33

Heating the wort to the boiling point of volatiles ## Footnote Stripping can be done with steam or gas.

Question 34

What is the best method for acidification of wort?

Answer 34

Adding acid directly ## Footnote Lactic or phosphoric acid are preferred.

Question 35

What is required for activation of foam stabilising proteins?

Answer 35

Temperatures below boiling held for longer periods ## Footnote Protein Z may require more thermal load.

Question 36

What should be considered when omitting a wort boil?

Answer 36

The full role of boiling in brewing is not fully understood ## Footnote Omitted boiling may affect beer taste and attributes.

Question 37

True or False: A wort boil is essential for producing good beer.

Answer 37

True ## Footnote The theoretical exercise of omitting boiling may not yield desirable results.