Home Brewing: Mashing and the Boiling Process
July 25, 2014 by
Why do home brewers boil their
ingredients? Well, for the same reasons all
brewers, big and small, boil the ingredients: you
can't have beer without first cooking everything in
a brew pot.
Mainly, the boiling process is meant to
kill any bacterial contamination (sterilization), deactivate
enzymes, isomerize the hops and/or spices (bitters, flavors
and aromas), and provide for a reduction of proteins (which
can cause bitterness). During the boiling process we may
also add settling agents such as Irish moss. This helps
provide for a clearer, cleaner brew.
The predominant bacteria found in wort is
lactobacillus. This bacteria is eliminated courtesy
the heat of the boil. The antibacterial properties of
hops absolutely complete the sterilization function.
Enzymes break down the carbohydrates (dextrins)
of the grain sugars to a level in which yeasts can ferment
them. Early heating of the wort reduces the actions of
enzymes, while boiling completely halts enzymatic activity
and creates the carbohydrates found in the wort.
Incidentally, enzymes are proteins.
Proteins found in the wort are reduced
during the boil. Essentially, proteins and other
polypeptides intermix with tannins and polyphenols. A
vigorous boil helps this process since these microscopic
solids need to crash into each other in order to
assemble/coagulate. The more "crashing" the boil, the
better the reduction of proteins. And, since these
heavier elements fall to the bottom of the brew kettle, they
are mostly eliminated from the fermentor during the transfer
Hops are added during the boil at varying
times, and for varying reasons. There are basically
two types of hops found in the brew house: bittering and
aroma. Bittering hops are high in compounds that,
well... make the beer bitter. The balance between the
amount of bittering hops and sugars will affect the final
flavor of the beer. A smooth-tasting beer, for example
has been brewed with minimal bittering hops. An IPA,
on the other hand is notorious for heavy bittering.
Bittering hops are generally added
throughout the boiling process, and usually not until after
the hot break. Boiling breaks down (isomerizes) the
oils in hops, imparting the bitterness in the beer.
Aroma hops are added usually during the
final 15 minutes of the boil. The goal here is to
impart pleasing smells, such as orange, grapefruit, citrus,
peppery, piney, etc. If they were added early during
the boil, the aromas would be boiled out, affecting the
What is Mashing?
Mashing involves consolidating the grains
and water in a container - also known as a "mash tun" - in
an attempt to extract sugars to create wort.
Most new home brewers perform "extract"
brewing. In other words, there is no need for mashing
as this has already been done for them. They simply
add the containers of malt extract (sticky syrup-like
substance), and powdered malt (known as dry malt extract or
DME) to the brew pot and start the boiling process.
On the contrary, more experienced home
brewers want to emulate the methods of big brewing.
Their approach involves an all-grain brewing process.
And this means they are going to create a mash concoction
before the boil. This mash produces the malt extracts.
Grains added to the mash tun are almost
certainly milled (crushed) to the perfect size, allowing for
maximum starch surface area, which further increases the
amount of sugars ultimately extracted. The grains used
typically include malted barley, and sometimes corn, wheat,
ryr, sorghum, oats, and rice.
The water is first heated to a point
where, when added to the mash tun, it will break down the
starches in the grains for conversion into the sugars.
Care is taken to control the heat as too little won't permit
the enzymes in the malt to extract the sugars, while too
much will produce off flavors in the final beer. While
most new home brewers heat the wort to around 150 - 155
degrees F., more experienced ones do a step infusion whereby
the temperature is maintained several times before
Example: A 15-minute rest takes place when
the wort reaches 115 degrees, keeping it at that
temperature. The temperature is then increased to
about 145 degrees F where it stays for 30 minutes.
Finally, the temperature is increased to around 160 degrees
F., where it remains for the final 30 minutes.
Mash Tun and All-Grain Brewing
A typical home brewing all-grain mashing
system will include a container for the heated water (sparge
water), a mash tun containing a false bottom for keeping the
grains out of the final wort, and a brew kettle.
Pictured is a cooler-type all-grain system from
Winning Homebrew. Realizing all home brewers have
their own methods for the madness, here is how we do it.
Like most home brewers, we usually make
5-gallon batches of home brewed beer. So, about 6 1/2
gallons of water is heated on a burner (stove top or gas
burner with stand) to around 180 degrees F. One quart per
pound of grain (10 pounds of grain = 10 quarts of water).
An amount of water is then added to the mash tun, creating a
After the temperature of the water falls
to around 170 degrees F., the grains are slowly stirred in.
After about an hour of "mashing", 6 gallons of sparge water
is heated to around 200 degrees F. and slowly sprinkled over
the mash. The idea is to "rinse" the grains of their
sugars, which have now been fully extracted.
While the sparge water is sprinkled upon
the grains, the flow of the wort coming out of the mash tun
(via a spigot at the bottom) is controlled to flow in an
equal amount. It is flowed directly into the brew kettle.
But, the first few cups of liquid being extracted will
contain some grain material. To eliminate this from
the brew kettle, it is poured back onto the top of the mash.
The resulting 6 gallons of wort is then heated to a boil,
where it eventually loses 3/4 - 1 gallon of water to
The remaining wort is chilled with a wort
chiller to a temperature where yeast will thrive. It
is then added to the fermenting (carboy or plastic bucket).
Yeast is added, or "pitched" and the mixture is vigorously
stirred and aerated. Maximum oxygen is needed by the
yeast. An air-lock is added and the beer is allowed to
ferment for 7 to 10 days.
Types of Mashing
Brewing beer may involve two types of
mashing: infusion and decoction. Infusion mashing sees
the grains being heated in a single container.
Decoction mashing has some of the grains boiled before being
added to the mash, thus increasing the temperature of the
Boiling the Wort
After mashing, the resulting wort mixture
is then sent to the brew kettle for boiling. Mainly,
boiling isomerizes the hops and kills any bacteria.
Again, about 6 gallons of wort liquid is boiled since some
will be lost to evaporation. Also, a bit may be left
behind in the brew kettle with the solids. The goal is
to have around 5 gallons of brew for fermentation.
Be careful with your boil as it will have
a tendency to boil over during the first 10 minutes of so.
This is called the hot break. Hot break is basically
all the foam and brown scum that collects at the to of the
boil. It consists of proteins and tannins, mostly.
Within 5 or 10 minutes, this foam will reduce and eventually
collect at the bottom of the brew kettle, forming the sludge
During the boil, you will be adding your
hops, usually at scheduled intervals. The early
additions will include your bittering hops, while those you
add at or near the end of the boil are your aroma hops.
Adjuncts, such as corn sugar, Belgium
candi sugar, and/or syrups may be added during the boil as
Depending on the PH of the water used in
the boiling process, a small measure of gypsum may also be
added to the brew pot. Gypsum will counter the
precipitation of calcium phosphates during the boil.
Typically, gypsum is used in all-grain brewing and not
extract brewing. In order to use gypsum, one must know
the PH level of the water being used, and the desired PH
level. For example, if you are brewing a Kolsch style
of beer, you will want to know the PH level of your local
water as well as the water in Cologne, Germany (where Kolsch
beer is brewed). A quick calculation will tell you how
many grams of gypsum you need to add to the brew kettle.
Settling agents, such as Irish moss, are
also added during the boil, and usually near the last 15
minutes. Irish moss helps coagulate the solids in the
brew kettle. When the wort is chilled, these solids
fall to the bottom of the kettle, making for a cleaner
extraction of wort to the fermentor.
Care is taken when adding Irish moss or other settling
agents. Too much can reduce the proteins to a level
that hinders the beer's ultimate head formation and
When the boil has completed - usually 60
to 90 minutes - it is time to chill the wort. This can
be accomplished with an ice bath. But, a wort chiller
(pictured) is recommended. The quicker the wort is
chilled to yeast-pitching temperature (around 75 degrees for
ales, and 45 or 50 for lagers), the less likely bacteria can
be introduced. Fast chilling will also eliminate hazy
Once the wort has been chilled, it is
moved to the fermentation vessel. This can be done via
an auto-siphon (or regular siphon). Often, the liquid
is "man-handled" and poured directly into the fermentor.
Either way, care is taken to reduce the amount of trub
(solid matter) that passes to the fermentor.
After you boil your home brew ingredients,
the next step in the home brewing process is