An image of the How Brew logo.

Home  |  Beer Brewing Kit  |  Brewing Supplies  |  Kegerator  |  Beer Styles  |  Beer Recipes  |  Craft Beer  |  Hops  |  Beer Glasses  |  All-Grain Brewing


Home Brewing: Mashing and the Boiling Process

July 25, 2014 by Rick Morris:

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 of wort.

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 desired smell.

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 increasing. 

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 BrewingAn all-grain home brewing setup includes the brew kettle, sparge water container, and mash tun.

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 doughy mixture. 

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 evaporation.

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 wort.

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 (trub) layer.

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 well.

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.The wort chiller most home brewers use to cool the boiled wort.  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 retention.

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 beer.

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 pitching yeast...

Learn How to Brew Beer at Home in 5 Easy Steps

Sanitize Home Brew Equipment
Mashing and Boiling
Pitching Yeast
Bottling & Kegging Beer

The Home Brewing Process
Instructions on Brewing | Videos 


Home  |  About  |  Contact

Copyright 2012 - 2014 - All Rights Reserved.  Two Monks Brewing - Canton, North Carolina