In a very generalized sense, all beer is made using the same basic
steps. All beer begins as wort that is then fermented, aged, clarified
to some extent and packaged. The biggest difference between what is
done at home versus in a big brewery is the equipment used. Commercial
brewers use multi-roll or wet milling to crush their grains. Wet
milling can be performed more than one way, but most wet mills these
days have a steeping tank above the mill where malt is sprayed with
water to increase the moisture content of the husk. After the malt
passes through a single set of rolls it is hydrated with mash water and
the mash is then pumped directly to the mash mixer. Many breweries use
adjuncts like rice and corn and these are often milled using special
Mashing is basically the same process, except most
commercial breweries use steam-heated mash mixers with special
agitators that help keep the mash uniform in temperature while at the
same time not beating up the malt so that wort separation runs
smoothly. Brewers who use adjuncts have to boil the adjunct in order to
gelatinize the starch and it is common to have a cereal cooker and a
mash mixer when adjuncts are involved. In fact, this set up is
basically the same as a decoction brewhouse that has a decoction kettle
and a mash mixer. One big difference in the whole mashing and lautering
steps is that ingredient yield is closely monitored. Most commercial
breweries achieve at least 92% of laboratory yields and many breweries
are pushing yields that are nearly equal to the theoretical laboratory
Most American breweries use lauter tuns to separate wort from malt
solids while some use mash filters. Lauter tuns used in commercial
breweries have slow moving rakes that gently cut through the grain bed
to facilitate wort separation and then the same device is used to move
the spent grains out of the lauter tun and into a pump that takes the
grain to a spent grain storage area.
Some smaller breweries, especially pub brewers, use infusion mash tuns
for mashing and wort separation. This is much more akin to what is done
at home. It is common for the brewer to use a mash paddle when mashing
in to evenly lay down the mash and to use some sort of hoe to remove
the spent grains from a door in the side of the mash tun after mashing
is complete. Then the plates are removed and the mash tun is given a
good cleaning. There is a lot of brewpub equipment that actually grew
out of homebrew equipment.
Mash times are similar. In fact many pub brewers mash-in, take a short
breather and begin wort collection. My old professor from University of
California-Davis is the one who started pushing this idea. The reason
it works is that there is no mash-off step and as long as the wort
collected in the kettle is not prematurely heated, conversion of
starchy worts continues in the kettle during wort collection and the
amylases in the mash are active during almost the entirety of sparging.
Brewers doing this use much shorter mash times.
Wort boiling also uses different equipment because of the much larger
batch sizes. Small pub operations use either steam heated or flame
heated kettles that are not much different than a big pot with an
external heating jacket. As kettles get larger than about 1,000 gallons
(3,800 L), more heating surface is needed than that available on the
exterior of the kettle. Internal or external heat exchangers called
calandrias are used to increase the heating area and the boiling wort
exiting the calandria is directed to a wort spreader (the cone-shaped
“hat” seen on top of the giant kettles) that fans wort out over the
surface of the boiling volume. This helps to knock down foam as well as
creating a large surface area for DMS to evaporate and exit through the
kettle stack, or exhaust pipe. Some kettles are even pressurized and
other designs cycle the pressure up and down to create uniform,
nucleate boiling periods when the pressure is released. Most commercial
breweries boil for 60–90 minutes, even with some of the newer kettle
designs. The trend, however, is towards reduced evaporation rates. The
old standard was 8% per hour and many new kettles are being designed
for a total evaporation of 4% or less. Certain laws in Europe are
really driving this because of energy penalties being imposed on
breweries who buy new equipment designed for high (>4%) evaporative
Hop separation is also different for commercial brewers because of the
larger batch sizes. Most beer these days is made using hop pellets and
these can be separated in large whirlpool vessels. Homebrewers can also
use the whirlpool method to help separate hop pellets and trub from
yeast. Breweries using whole hops typically use a hop separator that
strains the hops from the wort and continuously augers the spent hops
out of the device. Smaller brewers use hop backs that look very similar
to a mash tun.
Finally, the wort is cooled using a plate heat exchanger with enough
surface area to cool down the batch in anywhere from 30–60 minutes.
This means that the hot wort sits in the whirlpool vessel for a fairly
long time. After cooling, wort is aerated in-line with either filtered
air or oxygen and then flows into the fermenter. Many brewers inject
yeast in-line after aeration and others put the yeast in the bottom of
the fermenter where it mixes with the wort.
I would say that wort production in a commercial brewery is pretty darn
different than the way most homebrewed wort is made, either with
extracts or all-grain mashing. When it comes to fermentation and aging,
however, the process is pretty similar. One big difference is that
larger brewers typically ferment 4–6 batches in the same fermenter and
various techniques of yeast pitching and aeration are used when a tank
is filled over the course of 12–18 hours.
Another notable difference used by the largest breweries is the use of
a technique called high gravity brewing. This means that high gravity
wort, usually between 14–18 ºPlato (1.056–1.072 SG), is fermented and
later diluted with deaerated, carbonated water. The reason big
breweries do this is to reduce their fermentation requirements by up to
about 33%. Craft brewers typically do not use this method.
Aging is not much different at home unless we are talking about the
King of Beers and the use of beechwood chips in their chips tanks.
Anheuser-Busch is the only brewery that I know of who still uses this
once not so uncommon technique.
Next comes filtration and there are all sorts of methods used by
commercial brewers to clarify beer. Diatomaceous earth (DE) pressure
leaf filters, DE plate and frame filters, centrifuges and sheet filters
are the conventional methods. Many brewers use chill-proofing agents,
such as silica hydrogels and PVPP, at the time of filtration to protect
against chill haze and some brewers add isinglass finings before
filtration to improve filter run times. The most modern filtration
method is cross-flow membrane filtration and the aim is to eliminate
the use of DE in beer filtration.
Some commercial breweries even recover beer (called ruh beer) trapped
in the yeast cake. Not only does this reduce beer losses associated
with spent yeast but it also reduces effluent. This method is not
practiced by the majority of commercial breweries in the U.S. because
the quality of the beer may easily suffer due to yeast autolysis.
The last step is packaging beer into bottles, cans or kegs. Most large
breweries pasteurize their bottles and cans in a tunnel pasteurizer
after filling to kill any spoilage organisms that may be in the beer.
Some draft beer is flash pasteurized like milk before kegging.
As a general rule, craft-brewed beer made in the United States is not
pasteurized. There are a few craft brewers out there who do have
pasteurization equipment, but these are the exceptions. There is
nothing wrong with pasteurization when done correctly, but it does
prevent beers to be bottle conditioned because it kills the yeast.
Simply put, homebrewed beer and commercially brewed beer start with the
same basic ingredients and may taste very similar when poured into a
glass, but they arrive at that point by very different paths.