Subject: Head retention from Micah Millspaw
Date: 1992-06-03 19:51:00 GMT
There have been some questions about both head retention (beer)
and chill haze problems. I think that a large portion of the problem
is a lack of lipids in the wort.
Lipids are very important elements for proper beer stability.
Lipids are unsaturated fatty acids, this means that they are available
to form new bonds with other elements of the wort. Although only a few
ppm of lipids are present in finished wort, they can have far reaching
effects on factors such as yeast viability, ester formation, gushing
and flavour staling. Small variations in brewhouse procedure can produce
large variations in wort lipids. Lipids adhere to trub particles ( trub
contains up to 50% lipids) and to filter materials. Spent grains are high
in lipids. A turbid top runoff from the lauter tun can contain 5 times,
and even 40 times as many lipids as the clear wort runoff from the same
mash. Also yeast will autolyze if it does not receive small amounts of
ergosterol or unsaturated lipids.
North American grown barley malt contains very small amounts of
free fatty acids (3.2-3.5 mg\l) opposed to european malts (18-26 mg\l).
Insufficient fatty acid levels can result in high esters in the
finished product and can also be responsible for gushing problems in the
finished beer. The addition of unsaturated fatty acids can cure gushing.
While the addition of saturated fatty acids tends to increase gushing.
The content of unsaturated fatty acids has a strong influence on the
formation of fermentation volitiles, notably the acetate esters. A wort
that has been stripped of lipids could produce a beer too high in esters.
I beleive that a shortage of lipids may be a problem that
homebrewers encounter because of their obsession with mash extraction
yields. This need to eke out every trace of sugar from a mash, leads home
brewers to practice wort recycling and or flaufing. These can be risky
sparging techniques with regard to hot side aeration as well as stripping
lipids from the wort. Recycling is the collecting of the wort as it runs
out of the lauter tun and pouring it back over the grain bed. Many brewers
claim that recycling should be done to settle the grain bed. Flaufing is
the collecting of the wort as it runs out of the lauter tun, boiling it
and then returning it to the top of the grain bed. These practices not
only give oppurtunity for hot oxygen and wort reactions, but also strip
out fatty acids (which North American grown malts are low in) that are
essential for proper yeast nutrition.
I have long felt that mash recycling was a bad thing, in that
it tends to remove a lot of large particulate matter that would otherwise
be in the boil. I feel that these particles ( husks and grits mostly)
provide a place for proteins to clump onto during the boil and then
settle out more effectively in cooling.
I have observed much clearer finished wort (cooled) from my
boils, when the mashes were conducted with no recycling of wort than
from those of other brewers whose worts were made by recycling the mash.
Micah Millspaw 3/31/92
A lack of sufficient lipids will cause the finshed beer to have
stability problems one of which is head retention. Above it was mentioned
that additions of lipids could cure gushing, I would make it clear that
gushing is a head retention problem, and that it causes acn be the same
as those responsable for no head formation at all.
Micah Millspaw 6/3/92
ps. Look for more about how chill haze and haze in general ties in
with this in future HBDs.
The posts that comprise the Homebrew Digest Searchable Archive remain the
property of their authors.
This search system is copyright © 2008 Scott Alfter; all rights reserved.