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Subject: Lambic Digest #868 (June 12, 1996)
Lambic Digest #868 Wed 12 June 1996
Forum on Lambic Beers (and other Belgian beer styles)
Mike Sharp, Digest Coordinator
Contents:
AHA Talk part 6 (Jim Liddil)
AHA Talk Part 7 (Jim Liddil)
AHA Talk Part 8 (Jim Liddil)
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Date: Tue, 11 Jun 1996 7:43:34 -0700 (MST)
From: Jim Liddil <JLIDDIL at AZCC.Arizona.EDU>
Subject: AHA Talk part 6
Oak Barrels
The vessel used by traditional lambic brewers to ferment
their beer in is the European oak barrel. Oak barrels are
considered the ultimate vessel by many homebrewers making
lambic-style beers. The oak barrels used by lambic brewers
are generally used wine barrels of European origin. They
have had the majority of tannins and other wood related
compounds leached out of them by wine fermentation. The
traditional lambic brewer has various barrels, many of which
are quite old, with the size usually being 600 liters or
so.
The advantage of an oak cask over other vessels is that it
provides a microenvironment where the various yeast and
bacteria can grow. This is due to the porous nature of the
wood, which provides nooks and crannies for the
microorganisms to inhabit.(20) The permeability allows the
slow diffusion of air into the fermenting wort and this may
further aid the growth of the microorganisms as well as
flavor development. After a cask has been used for a number
of batches it will become, one hopes, infected with the
right microflora further aiding in the production of a more
authentic product.
It also seems that as a cask is used for many years the
various flavors from previous batches of beer as well as
those from the yeast and bacteria build up in the wood and
further add to the complex flavor profile of each successive
fermentation. It is felt by some that even old oak adds a
certain minor astringent note to the lambic from the
remaining tannins that are slowly leached from the wood.
The homebrewer has to consider a number of things before
obtaining an oak barrel. One has to consider the size, the
type of oak (American or European), where to put it and
whether to get a new or used one. First let s look at the
type of oak barrel to buy. Regardless of whether you
choose to buy a barrel made of American or European oak,
make sure it is a wine barrel that is uncoated. Do not buy
a whiskey barrel as they are charred on the inside and
really only meant for making whiskey. Do you really want
that burnt wood flavor in your lambic-style beer? Your best
bet is to buy the barrel from a cooperage rather than
through a homebrew supplier. That way you can get
specifically what you want and also save some money.
It is generally felt that European oak is superior to
American oak. This is based on the fact that American oak
trees and European oak trees are different species (21).
This leads to them having different profiles of the various
compounds that are extracted during the fermentation
process. The grain structure and thus porosity of the two
species is also different. It is felt that American oak is
too oaky as compared to European oak. There is some
truth to this, but in the past few years things have
changed (22). Part of the problem with too much oakiness
in American barrels has to do with the way the wood is
dried and aged. European cooperages have traditionally
aged their wood for at least 2 years before it is used to
make barrels. During this drying and aging process many of
the oaky compounds are volatilized from the wood.
American cooperages on the other hand quite often oven dry
the wood in a matter of days and then used it to make
barrels. This leads to an over abundance of oak character
left in the wood. Some cooperages still use this method for
their less expensive barrels. Others have started to
follow European practice and are aging their wood for
extended periods. Unfortunately most of the cooperages in
America that age their oak don t make barrels in any size
less than 200 L. If you are looking for a barrel of 5-15
gallons you will probably have to do some calling around to
see if you can find a barrel in stock made of aged wood.
Small barrels are not kept in stock by many cooperages
because demand is relatively small. Also it is no surprise
that many of the cooperages are in California due to the
large wine industry there.
Another factor to consider is the cost of European vs.
American oak. The majority of European oak barrels come
out of France and currently the franc is pretty weak. An
investigation of prices for barrels revealed that most
European barrels cost almost twice as much as equivalent
American barrels. If cost is no object and you are in the
market for a new wine barrel then of course go ahead and buy
a barrel of European origin.
If you choose to buy an American barrel make sure it is a
wine barrel. Again try to find one that is made from air
dried wood, preferably of a year old or more. Also get the
barrel with a medium toast This is a process where the
insides of the staves of the barrels have been lightly
browned but not charred as with a whiskey barrel. This is
done to barrels that are destined for red wine production
since it further reduces the tannins and oakiness of the
wood. Since a barrel is a major investment ask to speak to
a cooper about how to prepare the barrel. Ask what will be
done if the barrel fails to hold water when you fill it.
Will they exchange it for a new one? Most cooperages have
people on staff willing to discuss how to prepare a barrel
and are willing to provide an exchange for a leaky barrel.
If you buy a barrel from reputable cooperage leaking should
not be a problem anyway. Barrels come in a range of sizes
starting at around 3 gallons and going up to 50 gallons or
more. Typically though, European barrels do not come in
sizes smaller than 25 liters.
If you choose to buy a barrel remember that it is going to
have liquid in it for a year or more. It will need to be
in an environment that does not freeze or exceed 80 F (27
C) as these are the general extremes in temperature
encountered in Belgium. A barrel full of beer is going to
weigh 8.3 lb./gallon of liquid plus the weight of the
barrel. If you choose to buy a 10 gallon or larger cask
think about the logistics of filling and storing it ahead
of time. Due to the weight you may need a hoist or a few
strong friends to lift it. Also be sure you have the
brewing capacity to fill the barrel. It is not a good idea
to partially fill the barrel. This may lead to drying of the
staves and leakage.
The price of a barrel does not increase linearly with size.
Typically a 10 gallon one is only about $20-30 more than a
5 gallon size. This holds true whether you buy American or
European. Most of the cooperages selling American oak
barrels designate the size by the gallon capacity whereas
the dealers of European barrels designate size by the
liter. This is just another point to consider when
investigating a purchase.
Another source of barrels is previously used ones. Many
wineries in the US use 200 or 225 Liter European barrels
and you can pick them up for around $50 used. This
requires you live near a winery and that you have the
brewing capacity to fill it and the storage space. Many
wineries only use the barrels for 3-4 years before selling
them. The trend toward using barrels for a shorter time has
come about due to the decreasing use of sulfites and the
increased risk of Brettanomyces infection this can bring
about. Thus you can get a barrel in really good shape for
an excellent price. Unfortunately finding used barrels of
smaller sizes is not so easy. Wineries and cooperages that
deal in used barrels usually do not have anything other than
200- 225L sizes. It seems wineries do use the smaller sizes
to keep wine in that is used to make up the ullage in the
big casks. But they use these small casks until they are
ready to be used as fire wood. So if you find someone with
a used 5 or 10 gallon barrel for sale that is in good shape
consider yourself lucky. Another source of used barrels
maybe home wine makers who might be getting rid of a used
cask. Finally note there is a company that is
reconditioning the larger used barrels and downsizing them
to 30 gallons. (See Barrel Supplier List)
Some people warn that any beer made in an American Oak
barrel will taste like an oak branch. They also feel that
it will take numerous batches of beer to extract all the
oakiness from the wood. You will have to make a personal
decision regarding American vs. European Oak. Regardless
of what you buy you want the majority of the oak character
removed from it prior to using it. The quality of a
European barrel is not necessarily twice as good as an
American one either. Any barrel, if well cared for will
last for decades. To reduce the chances of oak beer you
will want to buy either a used barrel or a new one that is
made from air dried wood with a medium toast interior.
Regardless of the source any new barrel is going to have a
certain degree of oak character that will be imparted to
the beer. This is particularly true in the making of
lambic-style beer, where the wort stays in the barrel for a
long period of time. During this time period a great
amount of chemical compounds can be extracted out of the
wood. So it is suggested that you chemically strip the
barrel. When you first get the barrel you will need to
swell it with water to make it liquid tight. It is at this
stage when you find out if the barrel is of good quality or
not. At first you will need to top up the barrel daily as
the wood swells and absorbs water. It may leak some at
first, but should stop after 3-5 days. Once a good quality
barrel has been swelled it should show no further signs of
leakage unless damaged.
To maximize the amount of oak compounds leached out of the
wood change the water in the barrel every three days for
two weeks. This also ensures no mold will grow in it. If
you live in an area that has high humidity you may want to
add metabisulfite from the start at the rate of 200 PPM.
After two weeks of soaking start the chemical stripping
process to really remove the oakiness. This is done by
adding sodium carbonate (washing soda) to the cask at the
rate of 1/2 ounce/gallon and letting it soak for a week.
Then drain the cask, rinse it well and repeat the process.
To maximize the extraction repeat this process for 4 to 6
weeks. At this point the water in the barrel should be
clear when drained as compared to the tan liquid when you
start the process. Next neutralize any residual sodium
carbonate by adding citric acid to the cask full of water
to drop the pH to 3 and let it set for a few days. Then
rinse it well and fill it with metabisulfite solution to
inhibit mold growth until you can brew and fill it with
wort.
Following this stripping procedure can help you reduce the
chances of having multiple batches of oaky beer. If you
get the right barrel and are careful to strip it thoroughly
there is no reason not to use a barrel of American origin.
Besides, even a European barrel will need to be stripped to
some extent to reduce the oakiness that is present in any
new unused barrel.
So now you have a barrel and it has been full of beer for a
year or two and you want to bottle the beer. What do you
do with the barrel once it is empty? First you should
never leave a barrel that has held liquid empty for any
period of time as it will dry out and shrink. This may
lead to leakage that will not ever stop. Sometimes a leak
can be stopped by hammering the steel bands of the barrel
closer to the center. You will be better off if this can
be avoided.
Since lambic-style beer takes so long to ferment and age,
when you bottle is not very critical. You will be better
off if you coordinate when you will empty the cask for
bottling to a time when you can brew a new batch to fill the
cask up again immediately. For example, the day you are
brewing you can transfer the contents of the barrel to a
carboy(s) or other holding vessel leaving as much of the
lees behind as possible. This will allow the beer a chance
to settle until you are ready to bottle anyway. Then you
can rinse the cask out with water and have it all ready to
fill when your wort is cooled. This way there is no chance
of the cask drying out and all the microflora in the wood
remain intact and happy. If you must empty the barrel and
cannot fill it immediately, rinse it with water and burn a
sulfur candle in it and bung it up tightly or fill it with
metabisulfite solution. Then when you have time to brew
rinse the cask well and fill it with wort.
A barrel is a major investment and can be ruined if it gets
moldy on the inside. Thus it is important to keep it
filled up close to the top at all times. This requires
making up the ullage at regular intervals depending on the
dryness of where you live. Also as previously stated, when
there is not beer in the cask keep it filled with
metabisulfite solution. Do not use bleach or iodophor as
these would likely taint the wood and kill all microflora
present in the wood.
The outside of the cask also requires regular attention.
Again depending on where you live the outer surface may
develop mold over time. You can spray the outside of the
cask with metabisulfite at regular intervals or whenever you
see signs of mold developing. Some people use a 200 PPM
bleach solution or 25 PPM iodophor. These are probably OK
to use as long as you do not saturate the wood with them.
Others favor applying linseed oil to the outside of the
cask. The important thing is to keep an eye on your
barrels and treat mold and mildew infections when they
develop. This is all part of taking care of a barrel so
that it will last for years. It would be a shame to have a
cask well infected with Brettanomyces and Pediococcus,
ruined by mold.
Oak Chips The contribution of the oak from a cask to the
flavor of lambic is considered to be minimal based on
discussion with various individuals. This is due to the
fact that the casks used are many times' decades old and
were previously used for wine fermentation. Thus they have
had the vast majority of tannins and phenolic compounds
leached out of them. This said, it is still felt by some
that the oak may add some astringent quality to the lambic.
If you feel that using oak may help contribute complexity
to the flavor of your lambic-style ale but do not want to
deal with a cask then you might want to consider using oak
chips. The are usually available from homebrew shops or
can be specially ordered. It is suggested you use toasted
chips and that you soak them in a couple of changes of
boiling water prior to using them in the fermenter. This
will help remove the majority of the oak flavor compounds
from the wood. You do not want beer that tastes like an
oaky Chardonnay. Preliminary experiments indicate that
after the chips have been exposed to lambic-style ale the
microorganism do invade the pores of the wood. This was
shown by taking the infected chips and washing them
thoroughly with sterile water. The chips were then added
to sterile wort from which Brettanomyces and Pediococcus
could then be recovered. Researchers have shown that the
microorganisms do indeed invade the pores of the wood (20).
This is another area wide open for experimentation.
Bottling
There is some variation in the way lambic, particularly
gueuze, is bottled in Belgium today. Many of the brewers
artificially carbonate, sweeten and pasteurize their beer
to produce a more consistent less aggressive product that
has a wider market appeal. In their beers the ratio of old
to young beer or top fermented ale is typically not very
high. The traditional brewers who make true refermented
gueuze also use various ratios of young to old lambic, but
never normal top fermented beer. The method used by some
involves the mixing of 50% two year old or older lambic with
50% young lambic of 6 to 12 months of age.(13) The beer is
then bottled and allowed to referment in the bottle for up
to two years prior to release. The method favored by the
Boon Brewery involves mixing 95% 2 year old lambic with 5%
2-3 month old lambic and then bottling. Frank Boon prefers
this method due to the fact that the 50/50 method can lead
to ropy and or hazy bottles that do not develop a
consistent character. This is not Brewing Art in his
opinion.
Those of us in the US rarely have the luxury of being able
to mix young and old lambic. So we have to make due with
what works for our other brewing, that is using priming
sugar of some sort. Of course if you do happen to have
lambic-type ales of various ages fermenting then of course
go ahead and try to blend and bottle them and see what you
end up with. Gueuze, being refermented in the bottle is
many times fairly highly carbonated, though there are
examples that are nearly flat. This is part of the Art
and variability of the process.
The problem with conditioning a beer in the bottle that has
been fermenting so long is that the number of viable carbon
dioxide producing organism may be very low. If this is the
case the beer may not become carbonated or only very
lightly. To combat this problem you may want to prepare a
fresh starter of Brettanomyces and/or Saccharomyces at the
time of bottling. Then you want to prime with enough sugar
to end up with a fairly carbonated product.(2.5-3 volumes
CO2) Using a cup of corn sugar can lead to adequate
carbonation after as little as two months. Other times
there may be little carbonation after two years. It would
not seem to be a good idea to add Saccharomyces at the time
of bottling since they do not survive through the lambic
fermentation process.(12) But those of us who have looked
at what is in the sediment of a recent Boon lambic have
discovered that the only yeast generally recoverable is
indeed non-cyloheximide resistant yeast, most likely
Saccharomyces. Boon fines his old lambic before adding the
young beer and in the early stage of the ferment
Saccharomyces is the dominant strain. Limited testing
indicates that this yeast is indeed acid and alcohol
tolerant.
As with other aspects of this type of brewing, and with all
homebrewing for that matter, you have a great deal of
latitude with bottling. There are some things you should
keep in mind though when you are considering transferring
your beer from the fermentation vessel to bottles or other
serving containers. If the beer has been fermenting for a
year or longer the viability of the microorganisms in the
beer may be low and/or may be predominantly bacteria and
not yeast. If the viability of the yeast is low and you
choose to bottle the beer unblended with corn sugar then you
may get little carbonation of the product. If the
predominant microorganisms present are bacteria then they
will utilize the sugar before any yeast and again you will
get little carbonation. This is because the predominant
bacteria in an older lambic-style ale will most likely be
of the homofermentative variety.(i.e. Pediococcus) As
described elsewhere, homofermentative bacteria do not
produce gas as they metabolize sugars. Again you can
possibly combat this problem by adding a fresh starter of
Brettanomyces along with a heterofermentative lactobaccilus.
Apparently there is a symbiosis between the yeast and
bacteria that can aid in carbonation.
You can choose to put your beer into bottles using other
traditional techniques or standard homebrewer methods. You
can also put your beer into kegs or other containers that
can be artificially carbonated, such as PET bottles using a
Carbonater (TM) or TAP-CAP(TM). You can also naturally
condition your beer in a keg and then serve it using CO2.
The choice is up to you and you need to make some decisions
regarding what you ultimately want to achieve.
Let s start with bottling, as it is still the traditional
technique used by lambic brewers in Belgium. As stated
before, as long as beer is fermenting in a vessel it is
called lambic. When it is bottled and refermented it
becomes gueuze or one of the fruit flavored derivatives.
Of course we are not making real lambic, gueuze, Framboise
or Kriek since our product does not meet all of the
qualifications of an authentic product. To make a
gueuze-like product the beer needs to be put into bottles
and refermented in a fashion not unlike standard
homebrewing practice.
If the beer is fairly old and has a thick pellicle of yeast
on the top and a large layer of yeast at the bottom of the
vessel then you may want to consider racking the beer.
Transfer the beer to another vessel, being careful to leave
as much of the top and bottom layers behind as possible.
Then you can let this beer settle for a week or so prior to
bottling. This technique allows you to minimize the amount
of sludge carried over into the bottles. Of course you do
not want a completely yeast free product as it will then
fail to referment in the bottle after priming. As stated
before one can run into problems with lack of viable
microorganisms in the beer. In a best case scenario the
beer will still have adequate numbers of viable yeast even
after settling. In that case you simply transfer the beer
once again to a bottling vessel and add corn sugar (enough
to reach 2.5- 3 volumes CO2). Bottle it and wait for it to
condition. Sounds simple, but unfortunately lambic-style
beer making does not always lend itself to simplicity,
especially when you are trying to make a product with good
flavor complexity.
------------------------------
Date: Tue, 11 Jun 1996 7:47:16 -0700 (MST)
From: Jim Liddil <JLIDDIL at AZCC.Arizona.EDU>
Subject: AHA Talk Part 7
Blending
Let s look at how the lambic makers in Belgium make
traditional gueuze. At the Cantillon Brewery they blend
70% old lambic and 30% young lambic. Old lambic is
beer that has fermented at least two years and young
lambic is beer that has fermented about 6 months. The
bottled beer is then allowed to referment in the bottle for
6-7 months or more until it is deemed ready. After
refermentation the beer has reached an attenuation of 90%
or more (15).
At the Boon Brewery things are done a little bit
differently. Frank Boon has a slightly different view of
the world and wants a more consistent product that has good
keeping qualities and a good appearance. To this end Boon
gueuze is made by blending old beer that has fermented at
least two years with very young beer that has only been
fermenting a few weeks. They are blended at a ratio of 95:5
respectively. Boon also clarifies the old beer prior to
blending. This gives a bottled product that is reasonably
clear and does not develop ropiness. The blending
technique requires that you use your hydrometer to determine
the extract in the old and young beer and then mix them
accordingly. (7,9). Then you bottle the mixture and hope
for the best. This technique requires that you have more
than one batch of lambic-style beer going at a time.
Using the fresh starter approach can still cause problems if
there is a large amount of bacteria in the beer at
bottling. They may consume the sugar before the yeast and
thus little or no carbonation will develop. To alleviate
this problem one can remove the bacteria by filtering the
beer prior to bottling at the 0.2 micron level. Then all
you need to do is add fresh yeast and sugar. Alternatively
you can prime with DME since it contains more than glucose,
the only sugar that the bacteria can utilize. The bacteria
will consume the glucose and then the Brettanomyces will
consume the remaining sugars and dextrins and carbonation
will develop. Or at least that is how it should work in
theory.
One can use the blending approach, but instead of using
young lambic you can use a standard ale that has been very
lightly hopped, if at all. You can measure the gravity of
the standard ale and the lambic-style ale and then blend in
the right ratio to give you enough extract to achieve
carbonation. As with the other techniques you can add a
fresh starter of Brettanomyces to aid in adequate
carbonation.
Homebrewers have at their disposal another source of
dextrins to use for priming in the form of maltodextrin
powder. This powder contains little glucose and maltose
and will eventually be hydrolyzed into fermentable sugars by
the Brettanomyces cellular enzymes. Standard priming rates
can be used for maltodextrin since it will ultimately
become primarily fermentable sugars given enough time.
One could use any combination of the above when bottling.
There is a great deal of experimentation left to be done in
this area of lambic-style ale brewing. Keep in mind that
lambic microorganisms grow slowly and it may take months or
even years for the product to reach equilibrium. Lambic,
unlike most other beers, continues to change for the better
with age, quite often becoming more complex and less harsh.
The key to lambic ale brewing is to be patient and go ahead
and start other lambic ales and allow them to age. In a
few years you may be rewarded with a very nice complex
product and then again you might not. The important thing
to keep in mind is that as a lambic-style ale referments in
the bottle chemical reactions are occurring that lead to
various flavor changes. These reactions occur at a fairly
slow rate, since many of them are catalyzed by enzymes from
Brettanomyces. Remember Brettanomyces grow slowly and
never reach very high concentrations in the fermenting beer
or in the bottle. This is one of the reasons why it takes
lambic ales so long to ferment and for proper flavor
development to occur in the bottle. Be patient!
Brewers in Belgium have a distinct advantage when it comes
to bottling their beer and achieving the right flavor. A
typical lambic brewery has many casks with lambic in them
from which the brewer can choose. This allows the brewer to
achieve the right flavor complexity and balance in his
product. If a barrel contains lambic that is too hard it
can be blended with softer lambic to achieve the right
flavor. The typical homebrewer does not have this option
available to him or her. Usually a brewer has one five
gallon batch going which is then bottled. Depending on many
factors the single batch may end up being too hard or too
soft in character. As a brewer you have a number of
options. You can brew lambic-style beer on a regular basis
and thus over time (years !) have enough lambic on hand to
allow you to blend. The other approach is to ferment a 5
or 10 gallon batch in one gallon bottles and hope the
resulting beers all differ in character to some extent.
Quite often none of these approaches is practical for a
homebrewer. But I will remind you that making lambic-style
beers is not about being practical or making beer in the
easiest manner. One must make a decision based on what he
wants to achieve when making this type of beer and how many
sacrifices one is willing to make in order to achieve a
product that has any of the flavor and complexity of the
real thing. The choice is up to you.
Sanitation
Homebrewers and brewers in general are concerned with
sanitation and about bringing wild yeast and bacteria into
their breweries whether by accident or deliberately. Such
concerns apply more to the professional rather than amateur
brewer. The homebrewer can easily take all his equipment
apart and thoroughly clean and sanitize it. The
professional does not have this luxury. Carboys, buckets,
hoses and other equipment can all be exposed to the
appropriate cleaners and sanitizers to eliminate any wild
yeast and bacteria. This writer brews all his beers using
HDPE and PC containers and has used the same containers to
brew lambic- style as well as other beers for the last 3 or
so years. Cross contamination has not been a problem at
all. It is important to clean and sanitize all equipment
thoroughly before and after each use. Make sure all
equipment is free from any dirt and grime and use an
appropriate sanitizer. After a container has had beer in it
for a year it is important to clean it well. Automatic
dishwashing detergent works well for this task since it
contains TSP as well as sodium hypochlorite. Thus it does a
preliminary job of sanitizing the container. You can then
soak the container overnight in your favorite sanitizer
and then rinse it out the next day. By following good
cleaning and sanitation practices you should not have to
worry about cross contamination. If you are concerned
about contamination you may want to have a dedicated set of
equipment for lambic-style beer brewing. For a more
thorough discussion of cleaning and sanitation you may want
to consult some additional references (18,19).
Enteric Bacteria Characteristics and Growth (new section)
During the first month of the spontaneous fermentation of
lambic beer the dominate bacteria consists of
enterobacteria. These bacteria grow very rapidly and effect
the growth of subsequent yeast and bacteria. They also
effect the flavor of the beer via the various metabolic
byproducts they produce.
The enterobacteria that have been found to be present in
lambic beer include Enterobacter cloacea, Klebsiella
pneumoniae, Escherichia coli, Hafnia alvei, Enterobacter
aerogenes and Citrobacter freundii. These are gram-negative
straight rods which are motile with the exception of
Klebsiella. There can also be non-motile variants of the
other species. They all are able to ferment glucose with
some producing gas while others do not. Most of them grow
quite well in the presence of air and are also able to
ferment lactose. These bacteria follow either a butanediol
fermentation pathway or a mixed acid pathway. This leads to
large amounts of lactic (~1500 ppm), acetic (~600 ppm) and
succinic (~275 ppm) acids along with 2,3 butanediol (~2000
ppm) being formed in the first month of the fermentation
(10, 23). They can reach levels of 1 X 108 cells /ml
during the first 30-40 days of the fermentation. After
this period the decrease in pH and the increase in alcohol
caused by yeasts of the Saccharomyces species causes them to
die off.
The various by products from the growth of the
enterobacteria can lead to various flavors described as
celery-like, parsnip-like, mushroom-like, smoky or mouldy
(10). These flavors are not removed by the fermentation
process. The various acid products described previously
also have an impact on the beer flavor contributing to the
acidic taste of the final product. In fact the majority of
acetic acid found in lambic beer originates in the first
month and is the byproduct of enterobacterial growth.
Typically enteric bacteria are considered pathogenic
(disease-causing) in humans. They are often considered the
cause of various forms of food poisoning. This is indeed
the case, with Salmonella being cause of the vast majority
of cases (24). The enteric bacteria found in lambic are
generally not considered pathogenic in people other than
those who have immune systems that have been compromised in
some way (i.e AIDS or immunosuppresive chemotherapy).
Research has shown that the kitchens of many peoples homes
harbor more enteric bacteria than their bathrooms. (24)
These bacteria include all those found in lambic along with
Salmonella. Meats, vegetables and kitchen sponges or wash
cloths have all been found to be highly contaminated, with
the later having particularly high bacterial counts. This
makes the kitchen an ideal environment for allowing the
introduction of enteric bacteria into ones wort.
Discussions among homebrewers about making lambic-style
beers have also avoided the subject of enteric bacteria.
This has been due to the fear of food poisoning and the
associated side effects. Again research would indicate that
anyone who brews in their kitchen does indeed end up with
some amount of enteric bacteria in there beer. The growth
of the brewing yeast and the subsequent reduction in pH and
increase in alcohol kill the bacteria off before they can
cause off flavors or other problems in the majority of
cases.
It can be argued that without enteric bacterial growth and
the subsequent depletion of glucose and production of
metabolic byproducts lambic would probably not have the
depth of flavor and complexity that it does. Because
homebrewers have been afraid of enteric bacteria they are
missing an integral part of the production process.
Studies indicate that the enteric bacteria have a profound
effect on the subsequent growth and flavor development in
real lambic. In order to achieve the same flavor profile
it would seem important to have this initial growth of these
bacteria.
In order to allow the wort to become infected with enteric
bacteria a reasonable approach would be to leave the
fermenter open near a kitchen sink for an hour or two after
the wort has cooled. Then the brewer should wait an
additional 24 hours before adding any yeast. This will
allow the enteric bacteria to gain a foothold and begin to
grow and multiply to a level that allows them to produce a
significant amount of metabolic byproducts and deplete the
glucose. After 24 hours the addition of a small amount of
yeast will ultimately lead to the enteric bacteria being
killed off. Again because the yeast will produce alcohol
and lower the pH of the wort to a level at which the
bacteria can no longer survive.
------------------------------
Date: Tue, 11 Jun 1996 7:50:38 -0700 (MST)
From: Jim Liddil <JLIDDIL at AZCC.Arizona.EDU>
Subject: AHA Talk Part 8
Brettanomyces Characteristics and Growth
Brettanomyces is considered one of the major yeasts
responsible for the flavor characteristics of lambic.
Typically the species most homebrewers use are either
Brettanomyces bruxellensis or lambicus. These yeast have
cell shapes that are usually ellipsoidal and can also be
cylindrical or elongated. They frequently form chains as
they grow also. These cells quite often form
pseudomycelium and grow as filamentous branched cells. (25,
26) This gives the cells the ability to float and form a
pellicle on the beer.
Brettanomyces have the ability to form acetic acid from
glucose under aerobic conditions. Thus when they grow on
calcium carbonate agar there is a visible zone of clearing
around the colonies. They demonstrate a negative Pasteur
effect. That is they demonstrate a higher production of
alcohol under aerobic conditions as opposed Saccharomyces
which show decreased alcohol production under aerobic
conditions (27). Brettanomyces also have cellular
dextrinases that allow them to utilize dextrose polymers
larger than the typical trisaccharides that can be utilized
by Saccharomyces. A culture of Brettanomyces has a
characteristic acetic, earthy, horsey aroma. These yeast
grow much more slowly than do Saccharomyces brewing
strains. Also they are resistant to cycloheximide unlike
most normal brewing yeasts. Brewers classify Brettanomyces
as wild yeast and typically do all they can to avoid
them. In normal brewing these yeasts will lead to various
off flavors described as phenolic, smoky and goaty. In
lambic beer these are desired characteristics.
Another aspect of Brettanomyces is their ability to
enzymatically catalyze the formation of esters from the
corresponding alcohol and acid. Thus ethyl alcohol and
acetic acid can be combined to from ethyl acetate and lactic
acid and ethanol can be combined to form ethyl lactate.
These are two of the primary esters found in lambic beer
(28, 29).
Pediococcus Characteristics and Growth
Of the lactic acid bacteria found after about three months
of fermentation, Pediococcus damnosus is the dominant one
in traditional lambic brewing. It is a spherical,
tetrad-forming, gram positive bacteria. Pediococcus is
described as a homofermentative bacteria because it
ferments glucose to lactic acid without the production of
carbon dioxide. As the Pediococcus grows the concentration
of lactic acid increases and can reach levels of 5000 PPM
or more in the lambic. This increase in acid is a slow and
progressive occurrence over a number of months.
Pediococcus is a very fastidious organism, meaning it grows
slowly and has complex nutritional requirements. Because
of this fact and the environmental conditions, the
concentration of cells is never very high, being only 1 X
106 cells/ml or less. Of course this is in reference to
spontaneously fermented lambic; cells numbers may be higher
in an artificially inoculated wort. The lactic acid as well
as diacetyl and acetoin that the Pediococcus produce
contributes to the complex flavor and aroma of lambic, with
the acid making the largest contribution. The levels of
vicinal diketones (diacetyl and acetoin) have been found to
be at or below taste threshold levels.(13)
Culturing and Maintaining Lambic Organisms
To brew lambic-style beer it is advantageous to know the
basics of yeast culturing. It is a further help to know
how to culture the various organisms specifically involved
in lambic fermentation. For the purposes of this article
the discussion will focus on the culturing of what are
considered by many to be the primary players in the
fermentation process. Besides Saccharomyces these include
species of Brettanomyces yeast and Pediococcus damnosus
bacteria.
Any type of Saccharomyces can be used for the primary
fermentation of a lambic- style beer, since it will
contribute little if anything to the overall flavor profile
of the finished product. One can find any number of
articles and books on how to culture these yeast and
maintain them in the home brewery. (25, 26, 30, 31, 32)
It is the other organisms involved which are more difficult
to culture and maintain without some experience and
knowledge of how they grow. The yeast of the Brettanomyces
species bruxellensis and lambicus and the bacteria
Pediococcus damnosus are microorganisms that require very
specialized nutrients and environmental conditions. It
should be noted that unless you are going to brew
lambic-style beers more than once or twice a year you may be
better off buying new cultures each time rather than trying
to maintain them in a home environment. If you do feel the
need to maintain the cultures at home then you should become
very familiar with the culturing of normal brewing yeast
first.
Both Brettanomyces and Pediococcus produce acids as normal
metabolic by- products and because of this they need to be
maintained on media which can help neutralize it.
Otherwise, the acid will lead to a large drop in pH and the
organisms will die. The most readily available food grade
acid neutralizing agent is calcium carbonate (CaCO3), also
called precipitated chalk. A concentration of 2% (2 g/100
ml) in the growth media or agar will provide adequate
buffering capacity. Calcium carbonate is essentially
insoluble though and this can present problems if it is used
in making wort agar. To prevent the CaCO3 from falling out
of solution before the agar solidifies, cool the wort-agar
solution to 113-122 F (45-50 C), with constant swirling,
prior to pouring it into the tubes or dishes. When CaCO3 is
used in liquid media one can gently swirl the media with
the culture growing in it once or twice a day to help
prevent any stratification of the acid in the solution and
aid the neutralization of it with the CaCO3. As the lambic
organisms grow in the liquid media the acid produced will
react with the CaCO3 causing it to be solubilized over time.
Even when a culture reaches maximum confluence there may
still be some CaCO3 unneutralized, but this is not anything
to worry about as the acid produced by the growth in the
main wort will dissolve it in time.
Brettanomyces Culturing
The Brettanomyces yeast can be grown on wort agar which
incorporates 2% CaCO3 as noted previously. The wort itself
should be of a gravity of approximately 1.040 and
preferably made from an all grain wort due to the possible
lack of nutrients in malt extract (5,6). Due to the
fastidious nature and acid production by Brettanomyces they
need to be transferred to new slant more often than do
Saccharomyces. It is recommended they be transferred to new
slants at least every 2 months. Longer intervals between
transfers may lead to cultures which are no longer viable.
Because of this frequent manipulation there is a greater
chance the yeasts themselves may become contaminated with
other yeast, mold or bacteria. Thus your sterile culture
technique needs to be very good and you need to pay
attention to details. If your culture does become
contaminated you can prepare a dilute suspension of the
yeast and streak it out on a petri dish which has wort agar
with 2% CaCO3 and also incorporates 10 ug/ml cycloheximide.
(Appropriate cautions inserted) As the colonies grow watch
for a zone of clearing around the individual colonies.
Agar prepared with calcium carbonate will be opaque and
white in color and as the Brettanomyces grow the acid they
produce will dissolve the calcium carbonate and create the
zone of clearing. Generally only non-Saccharomyces yeast
will grow on media with cycloheximide in it and those that
do grow and have zones of clearing around them are likely
to be Brettanomyces. You can then pick the colonies off
and re-culture them on cycloheximide-free media. This is by
no means a definite technique for the isolation and
characterization of Brettanomyces. Yeast such as Kloeckera
are also acid producers that will grow on cycloheximide
agar. If you have doubts at all then you may be better off
buying new cultures and/or locating a microbiologist who
will work for homebrew. The only absolute way to
characterize a culture is through extensive fermentation,
assimilation and morphological testing, don t believe it if
someone tells you otherwise.
Pediococcus Culturing
Pediococcus is more difficult to grow and maintain than is
Brettanomyces due to its more complex nutritional and
environmental requirements. Pediococcus grows best in
liquid rather than solid media and this increases the
chances for unseen contamination. Unless you have access
to a 1000X power microscope and have culturing experience,
it is recommended that you do not try to maintain this
bacteria at home for any length of time. MRS (deMan,
Rogosa and Sharpe) broth is the preferred media for growing
and maintaining Pediococcus over long periods. It is a
defined media that is rather expensive but provides the
necessary nutrients and buffers for optimal growth over
extended periods. Prepare the media as indicated on the
package. Sometimes bacteria can lose their hop resistance
if grown in unhopped media for extended periods. Thus if
you are going to try to keep cultures going over a period
of time it is suggested you add iso-alpha acids to the media
using some type of hop extract. Use of whole or pellet hops
leads to particulate matter which causes the media to
become cloudy and less than ideal for visual monitoring of
growth. A suggested level is in the 15-25 IBU range. A
minimum suggested passage interval is every month. Allow
the culture to grow for a week at room temperature and then
it can be stored at 4 C. Another method for storing
Pediococcus is the use of stab cultures. MRS media is
prepared using 1.5 % agar and put into tubes. The tubes of
solidified media are inoculated by using a needle or
inoculation loop to stab the bacteria into it. The
bacterium is allowed to grow at room temperature for a week
or so until signs of growth can be seen. Then the tubes
can be stored at 4 C. Whether you use liquid or stab
cultures you need to keep the tube caps screwed down tight
to limit air diffusion into the cultures and prevent
desiccation. There is no need to worry about pressure
buildup since Pediococccus are not gas producers. The same
caveats apply to bacteria culturing as for lambic yeasts:
you need the proper equipment and good technique.
If you are going to get serious about culturing
microorganisms used for lambic-style beers then you might
consider buying or building a laminar flow hood of some
type. This will allow you to work in a nearly sterile
environment. Fungi Perfecti is one of several companies
that sell them or you can build your own. (33)
Starters
Whether you choose to culture your own lambic microorganisms
or buy them, you will need to propagate them prior to
adding them to the wort. A wort of specific gravity 1.040
with 2% CaCO3 will work just fine for this purpose. You
may also want to add some hops, to achieve a range of 15-25
IBU. You should follow a scale up procedure for these
microorganisms so as to reduce the risk of other organisms
over growing the cultures. With lambic cultures one does
not have to make as large a starter as that used for normal
beer. Start with a volume of 1/4 ounce (~5 ml) and allow
the culture to reach confluence. When it has, add the
contents to a volume of 4 ounces (~100 ml) and allow it to
again reach confluence. At this point you can pitch or
scale up one more time to a volume of 1 pint (~450 ml).
Such procedures have also been outlined elsewhere (30, 31,
32). Be aware that Brettanomyces is a very slow grower as
compared to other yeast and generally does not develop a
large kraeusen head either. The starter should develop a
typical Brettanomyces aroma due to the various fermentation
byproducts. You should notice a distinctive acid aroma
along with aromas often described as horsey or mousey. The
starter will also develop an acidic, mousey, earthy taste
if the yeast is indeed Brettanomyces. As the yeast grows
the acid produced will cause the CaCO3 to dissolve and the
fine white precipitate from it will mostly disappear.
Due to the additional vitamin requirements of Pediococcus
you may want to add 10% apple or tomato juice to the wort
starter. Another alternative is to use 0.5% dried brewers
yeast. Yeast extract is even better due to its purity and
solubility, but it is expensive. Wort from a previous
brewing session with 0.5% yeast extract added works very
well. This gives a nice clear media in which one can
monitor the growth of the bacteria more easily. As the
bacterium reaches confluence a clear zone will develop at
the top of the liquid and the rest of the liquid will be
very cloudy due to the large amount of bacteria.
For other beers you want to pitch a large volume of yeast to
ensure a rapid fermentation and decrease the risk of
contamination by wild yeast and bacteria. Well,
lambic-style beers require you to throw caution to the wind.
Large starters of normal ale yeast, Brettanomyces and
Pediococcus are not required. If the yeast and bacteria
are healthy there is no reason they should not grow in the
wort using the small volumes as described previously.
Remember this beer will be in a vessel for a year or more
and the bacteria and yeast have plenty of time to grow.
Also as the acid producing strains grow they will kill off
any other organisms due to the lower than normal pH,
increase in alcohol and reduction in sugars that are
fermentable by other organisms. If you feel the need to
use larger starters to put yourself at ease then by all
means go ahead. Just remember the beer will still take a
year or so to develop the proper character.
------------------------------
End of Lambic Digest
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