Biological Defects

Question 1

Hydrogen sulphide

Answer 1

Typical descriptor: Rotten eggs, boiled eggs

Cause: yeast during fermentation, unhappy yeast, young beer, bacteria contamination

Appropriate: in low levels in burton ale and lagers

Resolve:

Question 2

Isoamyl Acetate

Answer 2

Typical descriptor: banana, watery, pear drop

Cause: yeast, under pitch, hot ferment

Appropriate: wheat beers

Resolve: proper pitch, control ferment

Question 3

Dimethyl Sulphide

Answer 3

Typical descriptor: creamed/canned corn

Cause: too short boil, boil covered, bacteria contamination, SMM produced in germination is precursor

Appropriate: small amount in some lagers and cream ales

Resolve: stronger/longer boil

Question 4

2, 3-Butanedione

Answer 4

Typical descriptor: butter, butterscotch, nutty, caramel

Cause: low ferment temp, premature racking, under pitched, lactic acid bacterial

Appropriate: sometimes in bitters, scotch ales, Czech pils, dry stouts, oktoberfests

Resolve: yeast will remetabolize to 2, 3 -Butanediol

Question 5

Acetaldehyde

Answer 5

Typical descriptor: green apple, cut grass, leaves

Cause: premature removal from yeast, premature flocculation, oxygen depletion, bacteria spoilage

Appropriate: just above threshold in Asian lagers

Resolve: repitch yeast, proper DO

Question 6

Ethyl Hexanoate

Answer 6

Typical descriptor: red apple, aniseed

Cause: produced by yeast, fruity ester, poor yeast handling, yeast stress

Appropriate: low levels-many beers, high levels-no beers

Resolve: proper yeast handling/use

Question 7

Yeast

Answer 7

Typical descriptor: bread, sulphurous

Cause: yeast in suspension

Appropriate: Hefeweizen, some hazy beers, all beers during fermentation, off flavour in high concentration

Resolve: filter, cold crash

Question 8

Ethyl Acetate

Answer 8

Typical descriptor: nail varnish remover, acetone

Cause: yeast in fermentation, wild yeast contaminant, non food grade plastics, high ferment temp

Appropriate: wild ferment beers, strong ales, dipa/tipa, high abv beers

Resolve: control ferment

Question 9

4-vinyl guaiacol

Answer 9

Typical descriptor: cloves, wheat beer

Cause: yeast, low ferment temps, pherulic acid rest, improper sani or rinse of chlorine sani, malt/yeast type,

Appropriate: signature in German wheats

Resolve: higher ferment temps

Question 10

4-ethyl guaiacol

Answer 10

Typical descriptor: smoky

Cause: brewing raw materials exposed to smoke, bacteria or yeast in fermentation

Appropriate: rauchbier

Resolve: proper sanitation/cleaning, proper grain selection

Question 11

Lactose

Answer 11

Typical descriptor: smooth sweetness

Cause: added to beer, unfermentable

Appropriate: sweet stouts

Resolve: don’t add to beer

Question 12

Sucrose

Answer 12

Typical descriptor: harsh sweetness

Cause: residual sugars not fermented, low attenuation

Appropriate: stouts, porters

Resolve: recipe development, control ferment for proper attenuation

Question 13

Ester

Answer 13

Typical descriptor: fruitiness

Cause: yeast

Appropriate: Hefeweizen, saison, Belgians

Resolve: control fermentation