hist-brewing: Re: acetaldehyde & diacetyl

BrewInfo brewinfo at xnet.com
Tue Apr 11 14:22:01 PDT 2000

Angus writes:
>my point exactly, though i must admid than when I've used more than 50%
>table sugar I've gotten other "off-flavors" than green apple
>(diacetyl/2,3-butadione) Belgian brewers very rarely use table sugar.
>They do, however, use candy sugar from time to time.  Kwak is one of the
>beers its used in.  I have personally failed to detect any hint of green
>apples in a Belgian beer so far though.

Both table and candi sugar are virtually 100% sucrose.  Buying white candi
sugar is a waste of money... just use white table sugar.

It also seems as though several people are confused by my previous statements.
It's not the addition of sucrose that lends the off-flavours/aromas... it's
when too much of the original gravity (OG) comes from sucrose or other
refined sugars and too little OG comes from malt.  Malt not only provides
sugars, but also amino acids and other nutrients.  Nutrient-poor (low Free
Amino Nitrogen, i.e. low-FAN) wort *CAN* result in beers that are high in
acetaldehyde, diacetyl, 2,3-pentanedione and/or other undesirable
fermentation byproducts.  It doesn't mean that they *WILL* produce these
byproducts -- it depends on the yeast strain, temperature, perhaps dissolved
oxygen levels... many factors.

Sucrose itself does not add any flavour to the finished beer when added to
the wort because it is flavourless other than being sweet and because it
is completely fermented unless the yeast are damaged or the yeasts' alcohol
tolerance is exceeded.

>As I have learned from this list and others, the 'green apple' flavour
>comes from acetaldehyde aka 2,3-butadione and maleic acid supposedly
>adds a sort of butter scotch-isch feeling/smell to a brew.

You are getting your beer chemicals mixed up.  Acetaldehyde is acetaldehyde...
the aldehyde associated with ethanol.  2,3-butanedione is commonly called
"diacetyl" and lends a buttery or butterscotch aroma/flavour and, at higher
amounts, a slickness to the palate.  The yeast don't actually produce
diacetyl, they produce alpha-acetolactic acid, which oxidises to diacetyl
*outside* the yeast cells.  Healthy yeast will absorb diacetyl if given
enough time and so long as there is not an excessive amount (Pediococcus
bacteria produce diacetyl also and when you have diacetyl from a Pediococcus
infection, I don't think that any amount of yeast can absorb that much
diacetyl.  There is also 2,3-pentanedione, which is related to 2,3-butanedione,
and has a "honey-like" aroma and flavour.  I believe there are some acceptable
alternate spellings of both of these chemicals.  Malic acid is just a fruit
acid (C4H6O5) common in apples, like citric acid (citrus fruits) and
tartaric acid (grapes).  I don't know if malic acid has an aroma... I've
never smelled it by itself only in a blend called "winemaker's acid blend"
which is 1/3 each of citric, malic and tartaric acids.

>The reason I thought the green apple flavour came from maliec acid is a
>misunderstanding in Swedish.  Trade names for chemicals isn't my strongest
>side.  However, If I were to ferment an apple cider with lager yeats (say
>BC munich lager) at room temp, would this yield a high % of acetaldehyde ?
>If so I'd love to try and make some cider with lager yeast since it imparts
>some, IMHO, lovely cider flavors when fermenting at higher temps.

Each yeast has its own character... Brewer's Choice #2007 is said to be one
of the highest acetaldehyde producers.  I would not recommend fermenting
lager yeasts at warmer temperatures on an entire batch of beer/mead/wine/cider
because you can never be sure what the outcome will be.  I suggest you use
a familiar yeast for the bulk of the batch and set aside a gallon to try with
a new yeast.

Of all the Wyeast (Brewer's Choice) lager yeasts, I only have experience
with Wyeast #2035 at high temperatures.  This yeast makes some nice esters
(fruity aromas) and adds no unpleasant character.  Some lager yeasts produce
unpleasant levels of of sulphury aromas/flavours when used at high


Al Korzonas, Lockport, Illinois, USA
korz at brewinfo.org

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