Off Flavours

Question 1

What does Diacetyl smell like

Answer 1

Butter or movie popcorn

Question 2

What does DMS smell like?

Answer 2

Canned corn or tomatoes paste

Question 3

What does Acetaldehyde smell like?

Answer 3

Green apple or emulsion paint

Question 4

What does Tans-2-Nonenal smell like?

Answer 4

Paper or cardboard

Question 5

What does 3-Methyl-2-butene-1-thiol smell like?

Answer 5

Skunk
“Lightstruck”

Question 6

What does infection usually smell like?

Answer 6

Spoiled beer, lactic acid, acidic acid
Could combined with other faults.

Question 7

Which off flavor smells like Cardboard or paper

Answer 7

Trans-2-Nonenal

Question 8

Which off flavor smells like emulsion paint

Answer 8

Acetaldehyde

Question 9

Which off flavor smells like canned cream of corn

Answer 9

DMS

Question 10

Which off flavor smells like butter or movie popcorn

Answer 10

Diacetyl

Question 11

Where does Acetaldehyde come from?

Answer 11

Naturally Produced during Fermentation. It’s the precursor created by yeast before ethanol creation.

Question 12

How does the brewer avoid acetaldehyde in their beer?

Answer 12

• Healthy Yeast will convert acetaldehyde to ethanol.
• Stressed, old, or unhealthy yeast may not be capable.
• Allow the yeast enough time to fully complete the fermentation process and to condition the beer

Question 13

Where does DMS come from?

Answer 13

• A flavour that can form in the brew house during wort production.
• SMM breaks down to DMS during boil,
• Pale malts have high concentration of SSM

Question 14

How does the brewer avoid DMS in their beer?

Answer 14

high temp and vigour boil will volatize DMS out.

Question 15

Where does DIacetal come from?

Answer 15

• Derived from yeast during fermentation
• Yeast produces precursor alpha-acetolactate, which slowly transforms into diacetyl
• Unsanitary conditions in brewing, fermentation, packaging, and draft-related equipment

Question 16

How does the brewer avoid DIacetal in their beer?

Answer 16

• Healthy yeast will reabsorb diacetyl during fermentation and maturation
• Stressed, old, and/or unhealthy yeast may not be able to complete reabsorption
• Proper sanitation in the brewhouse, cellars, and service area

Question 17

Where does Trans-2-Nonenal come from?

Answer 17

• Flavour derived from the breakdown of unsaturated fatty acids during malt and work production.
• The compound becomes more flavour active over time and is one indicator the beer may be past its shelf life.
• Time and warm temperatures will increase the development of T2N.

Question 18

How does the brewer avoid Trans-2-Nonenal in their beer?

Answer 18

Best control is to keep beer cold to limit the development of T2N
And drink beer fresh

Question 19

Which off-flavour is most likely to form in beer long after it has left the brewery?

Answer 19

Trans-2-nonenal is typically associated with beer that is very old and/or has been stored at warm temperatures.

Question 20

Which tasting technique is most effective for detecting extremely volatile flavours?

Answer 20

The distant sniff is the most effective tasting technique for extremely volatile aromas.

Question 21

Which flavours may result from mishandling beer before it leaves the brewery?

Answer 21

• DMS comes from compounds found in malted barley, and its formation can be controlled during the brewing process.
• Diacetal and Acetaldehyde come from Yeast, and their formation (and elimination) can be controlled during fermentation and conditioning.

Question 22

Which of the following flavours can be prevented with proper draft line maintenance?

Answer 22

Poor draft line cleaning is the most common cause of the flavours found in the Infection spike (diacetyl + acetic).