Part III, Section C: Phenols, Esters and Off-Flavors in Beer Flashcards
What are the 6 aromas and flavors caused by oxidation in beer?
BES Card #208
- Stale
- Old, wet cardboard
- Papery
- Winelike
- Sherry
- waxy, lipstick
What is ‘skunked’ or light-struck beer
BES Card #209
Beer becomes skunked when light (specifically the blue spectrum of sunlight or fluorescent light) comes in contact with the compounds that produce hop bitterness, producing a chemical called MBT. MBT is one of the most powerful flavor substances known to man. The pungent odor compound resembles that of the famously malodorous defense spray deployed by skunks.
What are the 4 aromas of lightstruck beer?
BES Card #210
- Skunk
- Must (a stale, stuffy smell. Your damp basement and dry, hot attic might both smell of must.)
- Burnt rubber
- Cat musk (Cats have two anal glands, one on either side of the anus, that produce a musky or fishy smelling material.)
What are 2 flavors associated with dirty draft lines?
BES Card #211
- Butter
- Vinegar
What are the 3 aromas and flavors of diacetyl contamination in beer?
BES Card #212
- Butter
- Rancid butter
- Butterscotch
Also: slick mouthfeel
Esters: what is the flavor of Isoamyl Acetate?
Banana; ‘Peardrop’
A pear drop is a hard candy popular in England, and it gets its flavors from an ester called isoamyl acetate. Why is that important? Well, esters are aromatic chemical compounds that are found both in wine and in certain foods. So if someone smells “pear drop” in their wine, they may indeed be identifying that ester.
Esters: what is the flavor of Ethyl Acetate?
Lightly fruity, solvent-like
As ethyl acetate intensifies, however, the aromatic perception can skew from pleasant and fruity to solvent-like and perfumy; abnormally high levels are therefore regarded as off-flavors. In addition to being produced by brewer’s yeast strains (Saccharomyces cerevisiae and Saccharomyces pastorianus), ethyl acetate is also produced in large quantities by the wild yeasts Brettanomyces, Hansenula, and Pichia via aerobic fermentation.
Ethyl Acetate is widely used in glues, nail polish remover, and other household solvents.
Esters: what is the flavor of Ethyl Caprylate?
Apple; fruity, floral, banana-like, pineapple-like, or even brandy-like in its pure state
Ethyl caprylate (also known as ethyl octanoate), contributes to beer aroma. It tends to go hand in hand with the development of a yeasty flavor that may or may not be desirable, depending on the concentrations and the style of beer
Esters: what is the flavor of Ethyl Caproate?
Apple-like with a note of anise; sometimes pineapple
Also known as Ethyl hexanoate
Esters: what is the flavor of Phenyl Ethyl Acetate?
Roses, Honey
Phenols: what is the flavor of 4-Vinyl Guiacol? (4VG)
Clove
Produced as a by-product of ale yeast in fermentation. Has a clove flavor, and is an important component flavor in hefeweizens but is seen as an off-flavor in most cases
Phenols: what is the flavor of Guaiacol and Syringol?
Smoke
These phenols are created not by yeast activity, but by kilning over wood fire and exposure to the smoke, as in rauchbier. These give a beer a smoky aroma and taste, sometimes described as campfire or barbecue potato chips.
Phenols: what is the flavor of 4-Ethylphenol (4-EP)?
farmyard, medicines, horse blankets and mice
This phenol is produced by the wild yeast type Brettanomyces and it reminds people of farmyards, medicines, horse blankets, and mice. It is seen as an off-flavor in most cases but a component of some Belgian ales and lambics. It is also found in arabica coffee.
Phenols: what is the flavor of 4-Ethyl Guaiacol?
Smoked meat, clove-like spicy character
Produced by Brettanomyces, and seen as an off-flavor in most cases. It also has interesting woody and sweet vanilla nuances.
What produces the flavor of banana or ‘Peardrop’?
An ester: Isoamyl Acetate
What produces flavors that are light fruity or solvent-like?
An ester: Ethyl Acetate
What produces the flavor of apple; fruity, floral, banana-like, pineapple-like, or even brandy-like in its pure state
An ester: Ethyl Caprylate (also known as ethyl octanoate)
What produces the flavor of Apple-like with a note of anise; sometimes pineapple?
An ester: Ethyl Caproate (also known as ethyl hexanoate)
What produces flavors of roses or honey?
An ester: Phenyl Ethyl Acetate
What produces the flavor of clove in hefeweizens?
A phenol: 4-Vinyl Guiacol? (4VG)
What produces the flavor of smoke, or smokiness?
Two phenols: Guaiacol and Syringol
What produces the flavor of farmyard, medicines, horse blankets, or mice?
A phenol: 4-Ethylphenol (4-EP)
What produces the flavor of smoked meat, or a clove-like spicy character?
A phenol: 4-Ethyl Guaiacol
How can you mitigate solvent-like off-flavors in brewing?
Solvent off-flavors are caused by out-of-control ester production. Ester production is increased at higher fermentation temperatures so often we will find solvent off flavors when a beer is fermented too hot.
To mitigate solvent-like off flavors you need to choose a yeast that has your desired level of ester production and also control the fermentation temperature to make sure it does not rise too high.
What produces the ‘green apple’ off-flavor in beer?
Acetaldehyde
Acetaldehyde, also called ethanal (note different spelling from ethanol) , is a common compound that comes in everything from ripe fruit to coffee. It is also an intermediate compound produced by yeast during fermentation. As fermentation progresses to completion, all of the acetaldehyde is normally converted to ethanol which is the alcohol in beer.
What is the flavor/smell of dimethyl sulfide (DMS)?
Cooked or creamed corn
What causes the flavor/smell of cooked or creamed corn?
Dimethyl sulfide (DMS)
What off-flavor does Acetaldehyde produce?
Green apples
With bottle-conditioned beers disturbing the yeast sediment can produce off-flavors. Old yeast sediment can become ‘autolyzed’. What would these flavors be?
Ground meat past prime or tire rubber
