Wtf are esters??

[Christianb17]

Ive been homebrewing for about 6 months and I keep hearing talk about esters. What are they?

 

[BeerCrafter2011]

A chemical that resembles the smell of bananas. Esters are usually apparent in very warm fermented beers.

 

[cfonnes]

Not only bananas. Clove, plum, and pepper are a few of the other tastes that yeast can make when allowed to ferment at the right temperature.

 

[Yooper]

Ester is just a word that describes the fruitiness in a beer. Many English ales have an estery profile, in a good way. Belgians, too.

From John Palmer's How to Brew:

Estery / Fruity
Ales are supposed to be slightly fruity, and Belgian and German wheat beers are expected to have banana flavor components, but sometimes a beer comes along that could flag down a troop of monkeys. Esters are produced by the yeast and different yeast strains will produce different amounts and types. In general, higher fermentation temperatures produce more esters.

 

[ao125]

http://dwb4.unl.edu/chemistry/smallscale/SS076.html

Description

Alcohols and organic acids are reacted in the presence of a dehydrating agent to produce esters, substances often recognized by their characteristic odors.

Background

Many esters occur naturally and can be derived from a variety of plants. Besides being used as food additives to enhance flavor, they are used in synthetic fragrances, industrial solvents, and as starting materials for plastics such as Plexiglas.

Esters can be prepared by reacting a carboxylic acid -- R-COOH, and an alcohol -- R'-OH. A couple of drops of concentrated hydrochloric or sulfuric acid are used as a dehydrating agent to catalyze the reaction.

Esters are named essentially as derivatives or salts of carboxylic acids, with the regular acid ending changed to -ate. The alkyl or aromatic group of the alcohol is named first.

Example:
acetic acid + methyl alcohol --> methyl acetate + water

Usually, the less expensive of the two reagents is used in excess to drive the equilibrium to the right and favor ester production.

 

[the_bird]

I'm pretty sure that the banana/clove flavor is technically a phenol - I'm sure someone that's a lot smarter than me can explain the difference between an ester and a phenol. For our purposes, they're both chemical compounds developed by the yeast that provide a certain characteristic. It's esters that make a British ale taste "fruity".

In practical terms, certain yeasts (notably British ale yeasts) produce higher level of esters. When you talk about a yeast being "clean," that's mostly code for "not a lot of esters." It's not just the particular strain, though - if you underpitch, or otherwise have unhealthy yeast, you can have more esters. Same if you ferment too warm.

They aren't inherently good or bad, it just depends on the style. They'd be a flaw in an American Pale Ale, but not (within moderation) in a British pale ale.

 

[xjmox14x]

http://dwb4.unl.edu/chemistry/smallscale/SS076.html

Description

Alcohols and organic acids are reacted in the presence of a dehydrating agent to produce esters, substances often recognized by their characteristic odors.

Background

Many esters occur naturally and can be derived from a variety of plants. Besides being used as food additives to enhance flavor, they are used in synthetic fragrances, industrial solvents, and as starting materials for plastics such as Plexiglas.

Esters can be prepared by reacting a carboxylic acid -- R-COOH, and an alcohol -- R'-OH. A couple of drops of concentrated hydrochloric or sulfuric acid are used as a dehydrating agent to catalyze the reaction.

Esters are named essentially as derivatives or salts of carboxylic acids, with the regular acid ending changed to -ate. The alkyl or aromatic group of the alcohol is named first.

Example:
acetic acid + methyl alcohol --> methyl acetate + water

Usually, the less expensive of the two reagents is used in excess to drive the equilibrium to the right and favor ester production.

I once made a butterscotch ester in chemistry. Our professor always cautioned us not to mix the nitric acid and glycerol that were on the carts...

 

[Christianb17]

Thanks for the help!

 

[SilverZero]

I once made a butterscotch ester in chemistry. Our professor always cautioned us not to mix the nitric acid and glycerol that were on the carts...

Nothing wrong with a little glycerol trinitrate. But Homeland Security might disagree on that point.

 

[unionrdr]

Lolz silver. "But I'm only using it to brew in my ales! honest!"...as the FBI drags you off in their black sedan...friendly stranger my a$$.