Beer Off-Flavours Cheat Sheet!
Why Does my beer taste bad?
That is the million dollar question and one of the most googled searches from homebrewers! Well there could be a lot of causes, but there is always common factor, something has gone wrong and its made an "off-flavour!" so here we have compiled our off-flavours cheat sheet to help you self diagnose what is going wrong with your latest homebrew! It also helps if you take heaps of notes when you brew so you can go back later to figure out what mightve gone wrong!
Step 1
Try and figure out what flavour / aroma it is that you are getting in your beer that doesnt seem right.
Step 2
Go through the list of off flavours below to identify the potential causes for that compound being formed in your beer, and use the process of elimination to identify what went wrong with your batch so that you can fix it for next time!
No. 1 Acetaldehyde
Cause
- Produced during the early stages of fermentation when yeast is in its logarithmic phase and rapidly multiplying·
- it can also be caused by too much or too little dissolved oxygen being present in the beer during early fermentation·
- can also be produced by beer sitting on yeast cake for too long, when yeast health is poor they can burst open and release copious amounts of the chemical into the beer
Flavour / Aroma
- Fresh Paint
- Unripe green apples
- Freshly cut pumpkin
- Faintly cidery
How to prevent / Fix it
- Keep yeast healthy – don’t stress them out e.g.
- Pitch a sufficient quantity of yeast (don’t under or over pitch)
- Do not under or over aerate wort (no more than 1 min with a paint mixer is good)
- Keep temperature steady
- Do not rush fermentation allow it to completely finish
- Dump trub and yeast when needed, don’t let it sit on yeast cake for too long
No. 2 Alcoholic
Cause
- Higher weight fusel alcohols produced from fermentation when yeast is under too much stress
- Hot fermentation, typically in excess of 27 °C / 80 °F (unless it’s a yeast designed for hot fermentation e.g. Kviek)
- Very high gravity wort, especially when large amounts of sucrose or unrefined sugar is added
Flavour / Aroma
- Hot prickly alcohol, similar to the taste and smell of a cheap tequila
How to prevent / Fix it
- Keep fermentation within the appropriate temperature range for your yeast
- When adding adjuncts to brewing try not to increase the gravity too much with unrefined sugar
- Use a yeast starter where possible to build a healthy yeast culture and acclimatise yeast to wort before pitching
No. 3 Diacetyl
Cause
- A compound that is naturally formed during the fermentation process from diacetyl precursors, however in excess quantities it becomes apparent as an off flavour
Flavour / Aroma
- Butter
- Butterscotch
- Buttery microwave popcorn
How to prevent / Fix it
- Keep yeast happy and healthy by
- Not over or under aerating wort before pitching (no more than 1 min with a paint mixer is good)
- Ferment in the appropriate temperature range for your wort
- Do not rush fermentation
- Pitch a sufficient quantity of yeast (don’t under or over pitch)
- You can also help clean up diacetyl before bottling/canning/kegging beer by raising the temperature of your fermentation by 2-3 degrees for 2-3 days before packaging, this helps the yeast eat the last remaining sugars and absorb the diacetyl back into their cell walls
No. 4 Astringency
Cause
- Polyphenols (tannins) which react with the proteins in your mouth forming a “haze” coating your tongue, these polyphenols can come from:
- Over hopping with too many low alpha acid hops
- Over dry hopping
- Over sparging and/or sparging with water that’s too hot (above 80 °C / 176 °F)
- High mash pH and/or too
Flavour / Aroma
- Similar to bitterness
- Powdery / dry feeling
- Similar to sucking on a used black tea bag
How to prevent / Fix it
- Keep dry hop quantities to a reasonable level and reduce contact time between hops and fermenting beer (no more than 2-3 days) this can be done by trub dumping, or using a hop sock to remove hops after a set time
- Keep sparge temp to about 78-80 °C / 172-176 °F
- Stop sparging after sparge water is showing a gravity of 1.01
- Especially for stouts and dark beers check pH isn’t too high
No. 5 Estery / Fruitiness
Cause
- Either Isoamyl Acetate or Ethyl Acetate (depending on the fermentation) that is desirable in some beer styles but not all, resulting from excess Acetyle-Co A which is a compound yeast produce to convert nutrients (like fatty acids and sterols) into cellular building blocks during the logarithmic growth phase
Flavour / Aroma
- Banana
- Canned Fruit salad
- Nail polish remover (aroma)
How to prevent / Fix it
- Reduce factors that encourage excessive yeast growth and stress
- Ferment on the cooler side of the recommended temperature range for your yeast
- Aerate wort sufficiently before pitching yeast
- Pitch a sufficient quantity of yeast (don’t under or over pitch)
No. 6 Medicinal
Cause
- Can be from either
- Use of Chlorine or Iodine based cleaning chemicals that are not thoroughly rinsed out of equipment
Or
- Yeast being used too many times – resulting in a strain that has changed and mutated over usage, as well as likely been infected by wild yeasts, bacteria or fungi
Flavour / Aroma
- Band-aids (plastic strips for cuts an wounds
- Hot plastic
- Cloves (cooking spice)
How to prevent / Fix it
- Thoroughly rinse and clean out equipment after using chlorine or iodine based chemicals
- Check that your city water isn’t too high in chlorine, if so use a known water source that doesn’t (e.g. RO water (reverse osmosis water))
- Don’t re-use yeast for too many generations (no more than 10!)
