Faults and hygiene
Spotting off-flavours, working cleanly and fixing problems. 14 terms.
Acetaldehyde
- Off-flavour of green apple. Typical of beer that is too young and was bottled too early, or of stressed yeast. With a little more time on the yeast it usually disappears by itself.
Chill haze
- Haze that only appears in cold beer and disappears when it warms up. In the cold, proteins and polyphenols bind together. It is harmless. A vigorous boil, fast chilling and cold conditioning help prevent it.
Cleaning and sanitising
- Clean first: remove dirt and deposits with a cleaner and a brush. Only then sanitise, because no sanitiser works properly on dirt.
Diacetyl
- Off-flavour of butter or butterscotch, often with a slick mouthfeel. Yeast produces it in every fermentation and reabsorbs it afterwards if given enough time and some warmth. So do not end fermentation too early; for lagers a diacetyl rest helps.
DMS
- Dimethyl sulphide, smells of cooked corn or vegetables. It comes mainly from Pilsner malt and boils off, so boil vigorously without a lid for at least 60 minutes.
Fusel alcohols
- Higher alcohols that form when fermentation is too warm. They taste harsh and solvent-like. A controlled, not too warm fermentation temperature and enough healthy yeast prevent them.
Gushing
- Beer foams out of the bottle by itself when opened. Causes are too much priming sugar, bottling too early (fermentation not finished) or an infection. Keep affected bottles cold and open them carefully, as they can burst.
Hot side and cold side
- Everything up to chilling the wort is the hot side: the boil kills germs there, so clean is enough. Everything after that is the cold side: fermenter, tubes, spoons, airlock and bottles must be clean and sanitised.
Infection
- Unwanted bacteria or wild yeast in the beer. Signs are a sour or foul smell, a film on the surface or gushing. It usually comes from equipment that was not sanitised well enough after the boil.
Lightstruck (skunky)
- When beer is exposed to light, compounds from the hops change and it smells of skunk. Brown bottles protect well, green and clear ones hardly at all, cans completely. So always store beer in the dark.
Off-flavours
- Unwanted flavours. Common ones are butter (diacetyl, fermentation too short), solvent (fermented too warm), cooked corn (DMS, lid on during the boil) and vinegar or sour (infection from poor hygiene).
Oxidation
- When finished beer comes into contact with oxygen, it slowly starts to taste of cardboard or old paper and the hop aroma fades. So avoid splashing or shaking after fermentation, and keep the tube at the bottom of the bottle when bottling. Before fermentation, on the other hand, the wort needs oxygen.
Sanitisers (acid and quats)
- Make clean equipment free of germs. Acid sanitisers such as Star San need no rinsing and suit everything after the boil. Quaternary ammonium (quat) sanitisers work more broadly but must be rinsed off thoroughly.
Stuck fermentation
- Fermentation stops before the expected final gravity is reached. Common causes: too cold, too little or tired yeast, too little oxygen at the start or a hot mash that created a lot of unfermentable sugar. Moving the fermenter somewhere a little warmer and gently swirling it often helps; otherwise add fresh yeast.