Beer Faults Flashcards
Butterscotch, Caramel, Popcorn
(Caramel, Sweet)
Diacetyl
Typical origin:
- Intermediate fermentation product
- Produced during primary fermentation
- Too short or cold secondary fermentation
- Yeast flocculate, inactivate, or harvested too early
- Can also be formed by contamination (Lactobacillus and Pediococcus spp)
When appropriate:
- Dependent on concentration
- Desirable in some ales (dark, scotch), stouts and lagers, eg Czech/Bohemian Pilsner
- Considered as fault in most other beers especially lagers
Threshold: 10 – 40 μg/L
Typical concentration in beer: 8 – 600 μg/L
Treatment:
- Can be treated if detected early during lagering/conditioning and yeast is still active
- increase temperature and resuspend yeast
Prevention:
- Strict temperature control
- Enough time for primary and secondary fermentation. No short cuts!
- Ensure good viable yeast count in suspension in secondary Agitation
- Quality control (tasting) before chilling
- Prevent infection, good hygiene standards
Skunky, Catty, Fecal
(Rubber)
Lightstruck
Typical origin:
Photochemical reaction of ultraviolet light (< 520nm) or visible light with isohumulones followed by reaction of acyloin group with sulphur compound
When appropriate: Never
Threshold: 4 ng/L
Typical concentration in beer: 1-5 ng/L
Confusion: Mercaptan
Treatment: No treatment
Prevention:
Use cans or amber bottles over green or clear
use reduced iso-alpha acids, either rho-, tetra-,or hexaisohumulones
(special hop extracts)
Catty, Drains, Fecal
(Natural Gas, Garlic, Cabbage)
Mercaptan
Typical origin:
- Infection by anaerobic bacteria such as Pectinatusfrisingensis, cerevisiiphilus, Megasphaeracerevisiae.
- Yeast autolysis, degradation of sulfurcontaining amino acids.
When appropriate: Never
Threshold: 1 μg/L
Typical concentration in beer: 0-0.5μg/L
Confusion: Dimethyl trisulphide, sulphur dioxide
Treatment: No treatment possible
Prevention:
Good sanitation and hygiene practice
Move beer off of yeast cake after the end of fermentation
Metallic, Inky, Blood like
(Put drop on hand and sniff)
Metallic
Typical origin:
- Contamination with poor quality metals (tanks, piping, fittings, cans with poor quality coating etc.)
- Poor water quality (high ion concentration)
- Low quality or incorrectly stored malts: Oxidation of fats and lipids in malts can cause metallic flavour
- Less common: oxidation of fat from ingredients such as chocolate, nuts etc. during mashing or fermentation
When appropriate: Never
Threshold: 1 –3 mg/L (iron sulphate)Aldehydes = ???Typical concentration in beer: Trace levels
Confusion: Papery
Treatment: No effective treatment.
Prevention:
- Treat water properly
- Use food grade material including stainless steel, plastic, and glass
- Avoid using fittings, sealants, containers that can corrode
- Store malts properly (dry, dark, cold), use malts quickly
- Avoid fatty ingredients
Papery, cardboard, wet cardboard, shoe box,
(Taste like paper)
Papery
Typical origin:
Aging of beer.
Lipid compounds in beer from malt undergo auto-oxidation.
Process fault. Too much oxygen contact during processing.
Mechanisms not well understood
When appropriate: Never, especially bright, low-medium alcohol beers are most critical.
Threshold: 50 -100 ng/L
Typical concentration in beer: •< 50 ng/L in fresh beer >200 ng/l in aged beer
Confusion: Musty/cork taint (TCA)
Treatment: addition of sulfiteor ascorbic acid, depends on regulations of country
Prevention: Minimise oxygen contact during brewing (e.g. flush tanks with CO2), bottling and storage
Exemption: oxygenate wort when pitching the yeast
Store at low temperature to minimise oxidation rate
Add sulphite/ascorbic acid, depending on regulations of country
Allspice, clove, herbal, medicinal, smoky, plastic, vanilla, astringent
(Esters, Banana, Bubbble gum)
Smells like wheat beer
Phenolic
Typical origin:
Yeast through fermentation by–products
Microbial contamination, wild yeasts
Excessive sparging or over-crushing
Contaminated water
When appropriate: Low-medium levels in German wheat and rye beers, French and Belgian ales/strong ales. Barrel aging. Scotch ales or stouts
Threshold: 40 μg/L
Typical concentration in beer: -10-30 μg/L->40 μg/L (faulty/specialty beers)
Confusion: Vanillin, Benzaldehyde, eugenol
Treatment: No treatment
Prevention: Use of appropriate yeast strains
Belgian and hefeweizen yeasts produce more than other strains
Control of wild yeast infection with good hygiene practice
Use appropriate malts and sparging techniques
Limit use of wood, fruit, spice, roast malt
Acidic, sour, vinegar, citrus
Sour
Typical origin:
- Organic acids (main ones are acetic and lactic)
- Microbial contamination
- Yeast
- Malt, particularly acidulated
- Fruits added in brewing
When appropriate: Fruit beers, Berlinerweiss, Belgian sour beers (Lambic, Gueuze), sour beers
Typical beer pH: 4 –4.5
Confusion: Astringency
Treatment: Depends on the extent of sourness
Prevention:
Proper yeast management
Proper hygiene, i.e. avoid siphoning using mouth (lactobacillus)
Avoid oxygenation of green beer
Mashout and sparge at appropriate temperatures
Cooked vegetable, cooked corn, cabbage
(Corn, Olives)
Dimethyl Sulphide (DMS)
Typical origin:
- Malt, derived from s-methyl methionine amino acid during malting, degrades to DMS during boiling due to it being heat labile
- Microbial contamination by wild yeast or bacteria
- High levels of corn based adjunct
When appropriate: Low levels in lagers and pilsner styles.
Threshold and typical concentrations: 10-150 μg/L
Confusion: dimethyl trisulphide, ethanethiol, methyl thioacetate
Treatment:
- Before fermentation –boil longer and hotter
- During fermentation –high fermentation temperatures, ales
- After fermentation -none
Prevention:
- Good quality malts that are properly stored
- Use less corn adjuncts
- Rolling wort boil for proper amount of time (1-1.5 hrs) for evaporation
- Temperature control during whirlpool, and fast cold break
Rancid / spoiled milk or butter, Baby sick, vomit
(Corn chips, Vomit)
Butyric acid
Typical origin:
- Bacterial infection either during wort production or packaging by Clostridium or Enterobacter spp.
- Use of contaminated raw material especially sugar or sugar syrup contaminated with Clostridium
When appropriate: Never
Threshold: 3 mg/L
Typical concentration in beer: < 1 mg/L
Confusion: Isovaleric acid, cheese off-flavour (produces by Brettanomyces or hop oil oxidation)
Treatment: No effective treatment.
Prevention:
Good sanitation practice
Use of contaminant-free ingredients especially sugar (syrup)
Eggs, drains, putrid, rotten eggs, sulfidic
Hydrogen sulphide (H2S)
Typical origin:
- Yeast esp. lager strains
- Formation during wort boil
- Bacterial infections Zymomonas, Pectinatus, Megasphaeraspecies.
When appropriate: Very low levels in lagers. Traditional Burton IPA33
Threshold: 10 μg/L
Typical concentration in beer: 0-40 μg/L
Confusion: Isovaleric acid (cheese off-flavour produced by Brettanomyces or hop oil oxidation)
Treatment: Longer maturation of green beerPrevention:
- Sufficient yeast nutrients
- Carefully consider yeast strain
- Good sanitation practice
