Fault
Cheesy
A cheesy, sweaty aroma from badly stored hops whose beta acids have oxidised.
Also called isovaleric acid, sweaty, old cheese.
What it tastes and smells like
Responsible compound: isovaleric acid.
Where it may be expected
Lambic brewing uses deliberately aged hops, and a faint cheesy note from them is within the tradition. Anywhere else it indicates hops that should not have been used.
Intensity and context decide. In the styles below a restrained version of this can be part of the character; the same character running past that is still a fault there.
If you are drinking it
A cheesy aroma is a raw-material fault. Harmless but unpleasant.
Not a safety issue. Beer’s alcohol, hop compounds and low pH make it inhospitable to organisms that cause illness.
What causes it
| Cause | Stage | How often | Who can act |
|---|---|---|---|
| Hops stored warm or with air access, oxidising beta acids into isovaleric acid. | raw materials | most common | brewer |
If you are brewing it
- Brewer: Store hops vacuum-packed and frozen, and reject any that smell cheesy on opening. (prevents)
Where in the process this comes from
Steps that can produce this fault when they go wrong. Each links to what the step is for and how it is controlled.
- The boil — Boil the wort to isomerise hop acids, sterilise it, coagulate protein, drive off unwanted volatiles and concentrate the extract to the target gravity.
Often confused with
- Faded hop character — loss of hop aroma, dull, muted character