Beer Off Flavors

Question 1

Acetaldehyde

fresh cut green apples

Answer 1

Make sure fermentation is vigorous using healthy yeast. Allow full attenuation. Leave beer on yeast longer. Oxygenate wort fully. Try another yeast strain. Make sure sufficient yeast nutrients are available. Let beer age longer.

Question 2

Alcoholic/Hot

spicy, vinous, warming from Ethanol and higher alcohols

Answer 2

Lower fermentation temperature. Use a less attenuative yeast strain. Check yeast health. Use less fermentables. Use less sugary adjuncts. Check for possible infection. Raise mash temperature. Let beer age longer before consuming.

Question 3

Astringent

Mouth-puckering, lingering harshness, husk-like graininess

Answer 3

Don’t oversparge. Don’t overcrush grain. Don’t boil grain. Don’t sparge with water above 170°. Don’t sparge with
water with a high pH (over 6). Use water with lower sulfate content. Use less dark grains (especially black malt). Use less whole hops (especially high-alpha hops or simply large quantities of hops). Avoid use of raw spices, fruit pith and fruit skins.

Question 4

Diacetyl

Buttery, Butterscotch, Movie Popcorn

Answer 4

Try another yeast strain. Oxygenate wort before fermentation. Reduce primary fermentation temperature. Use a warmer/longer secondary fermentation. Use healthy yeast in sufficient quantity. Make sure sufficient yeast nutrients are available (including reducing adjunct use). Check for infection. Allow beer to rest on yeast until fully attenuated.
Don’t rack, filter or fine too early. Don’t crash-cool yeast. If lager, raise temperature for a diacetyl rest at end of
fermentation. Bottle condition beer at cellar temperatures. Avoid adding oxygen during fermentation.

Question 5

DMS (Dimethyl Sulfide)

Cooked corn

Answer 5

Use a long, rolling, open boil. Reduce amount of pilsner malt. Cool quickly before pitching yeast. Check for infection.
Make sure you use a healthy, vigorous yeast starter.

Question 6

Estery

Fruity (strawberry, pear, banana, apple, grape, citrus)

Answer 6

Lower fermentation temperature. Try a cleaner yeast strain. Oxygenate wort sufficiently. Reduce original gravity.
Check hop variety for fruity characteristics. Avoid carrying over excessive break into fermenter. Pitch a sufficient
quantity of yeast (avoid yeast stress). Bottle condition and age beer longer at cellar temperatures to reduce esters.

Question 7

Grassy

Fresh-cut grass, green leaves

Answer 7

Reduce dry-hopping or quantity of whole hops. Avoid oxygen pickup. Check hops and malt for freshness.

Question 8

Light-struck

Skunky, catty

Answer 8

Don’t expose wort/beer to sunlight after hops have been added. Don’t use clear or green glass bottles. Avoid use of Cluster hops in late hop additions.

Question 9

Medicinal (chlorophenolic)

Chloroseptic, medicine cabinet

Answer 9

Avoid water with chlorine or chloramines (use RO water if necessary). Avoid bleach sanitizers. Reduce
astringency/grain husk sources. Avoid excessive whole hop use. Check for infection.

Question 10

Metallic

Iron, copper, coins, blood

Answer 10

Check water for metallic ions. Reduce water salts. Check equipment condition for rust. Make sure stainless steel
equipment is properly passivated. Fully rinse sanitizer. Try using RO water and add salts as needed.

Question 11

Musty

Stale, moldy, cellar-like

Answer 11

Avoid oxidation (see Oxidized). Check sanitation. Avoid peat-smoked malt. Check water for freshness and taste. Use fresh ingredients (especially malt and hops).

Question 12

Oxidized

Stale, papery, cardboard

Answer 12

Check for oxygen being introduced into beer post-fermentation. Don’t splash when racking/bottling. Check caps
and/or keg seals for good fit. Purge bottles/kegs with CO2 prior to filling. Store beer cool. Drink beer when fresh.

Question 13

Plastic (Phenolic)

Band-aid, electrical tape, styrene

Answer 13

Check for infection. Check yeast strain and health. Lower fermentation temperature.

Question 14

Solvent/Fusel

Hot burning on palate

Answer 14

Lower fermentation temperature. Pitch a sufficient quantity of healthy, active yeast. Check for infection. Try a
different yeast strain.

Question 15

Sour/Acidic

Lactic acid, citric acid, sharp, clean sourness

Answer 15

Check for infection. Check yeast strain. Don’t mash for long periods of time at low temperatures.

Question 16

Smoky (Phenolic)

Smoke-like, charcoal, burnt

Answer 16

Check for scorched mash or boil. Check excessive use of dark malts. Check for infection.

Question 17

Spicy (Phenolic)

Clove, pepper, vanilla, etc.

Answer 17

Use a different yeast strain and/or hop variety. Adjust fermentation temperature (sometimes higher, sometimes lower, depending on yeast strain and beer style).

Question 18

Sulfury

Rotten eggs, burning matches

Answer 18

Check for infection. Check water for excessive sulfates. Check yeast health. Check for yeast autolysis (beer left on yeast too long at warm temperatures). Try another yeast strain.

Question 19

Vegetal
Cooked, canned or rotten
vegetables (cabbage, celery, onion, asparagus, parsnip)

Answer 19

Encourage a fast, vigorous fermentation (use a healthy, active starter to reduce lag time; this is often due to bacterial contamination of wort before yeast becomes established). Check sanitation. Check for aged, stale, or old ingredients (especially old liquid malt extract). Avoid oversparging at low temperatures.

Question 20

Vinegary

Acetic Acid, vinegar-like sourness

Answer 20

Check for infection. Check yeast strain. Check for oxidation sources (acetobacter is aerobic).

Question 21

Yeasty

Bready, sulfury, yeast-like

Answer 21

Use a more flocculent yeast strain. Allow yeast sufficient time to flocculate. Filter beer or use clarifying agents. Avoid carrying over as much yeast. Age the beer longer. Try another yeast strain.