Mixed Gas, sometimes called BeerGas, Aligal or G-Mix, is
the newest weapon in the arsenal of the Draft Beer Service person. Most
brewers recommend a mix of nitrogen and CO2 for higher-pressure draft
systems, condemning the use of air on beer completely. As with most new
tools there are a lot of misunderstandings about Mixed Gas. In this article
we hope to “clear the air” and to show how using mixed gas will
reduce headaches, save money and improve beer quality.
“The Brew House” in Helena saves $600 per month with mixed
gas!
The “Brew House” in Helena, Montana has 18 beers on tap, ranging
from pilseners to stouts, and they sell about 100 kegs of beer each month.
Theirs is a 60-foot glycol system dispensing beer at about 20 psi. When
they switched from pure CO2 to a mixed gas blend of 60% CO2 they began
saving $600.00 per month. The saving is a result of eliminating wasted
beer. In addition to the money saved they have noted the convenience and
ease of pouring. Quoting Bob White Owner/Manager of the Brew House, “Blended
gas has made a huge difference in our operation. There is almost no wasted
beer and we can no longer tell when a keg is getting empty; it pours perfectly
right up to the end.”
Revolution?
We see a new growing interest in beer in the US and especially in different
styles of beers and beer quality. There is certainly a trend toward more
beers on draft in each establishment. This places a strong emphasis on
draft service.
The purpose of any draft system and the goal of all draft technicians
should be to get the beer from the keg to the glass exactly as it came
from the brewery. The new appreciation of quality beer provides new
challenges for the people who distribute beer. Brewing is an art form
with a rich culture and history and Americans are appreciating this art
more each passing year. Beer wholesalers are the curators of this art.
The proper care of the product and the design, building, and maintaining
of draft systems will greatly enhance the quality of beer the customer
receives and the appreciation of the brewer’s art. It will ultimately
improve sales and profits for the entire industry. Mixed gas is an important
part of any high quality long draw draft system.
What is mixed gas? back to top of page
Theoretically, mixed gas is simply a blend of CO2 and some other gas.
In practice, nitrogen is the second gas of choice. In the past, air was
very commonly used as the second gas. Today we realize that air’s
advantage (low cost) is outweighed by its serious disadvantages. Air
ruins beer. Since all major brewers condemn using air to dispense
beer, it is a disservice and no longer acceptable for any beer wholesaler
or service company to use or recommend it.
Nitrogen’s advantages
Nitrogen is the perfect choice as a second gas for several reasons. Many
beers use nitrogen as an ingredient. The best-known example and the originator
of the concept is Guinness Stout on draft. The Guinness brewers go to
great pains to dissolve nitrogen in the beer, which improves the quality
of the head. Nitrogen (N2) is the ingredient responsible for the “whipped-cream-like”
foam in Guinness and other beers like Pyramid DPA, Boddingtons, Abbott’s,
Caffrey’s, Murphy’s Stout and Beamish Stout. N2, in the right
proportion, is required in the gas used to push these beers. Without it,
the dissolved N2 would come out of solution and these beers would not
be the same.
Nitrogen is one hundred times harder to dissolve in beer than CO2. While
this is a challenge for the brewers mentioned above, it makes N2 a good
choice for dispensing “normally carbonated” beers. N2 is not
readily absorbed, does not react chemically under normal circumstances
and will not affect beer flavors. N2 is 78% of the air we breathe, making
it safe and readily available. A relatively new product called a “Nitrogen
generator” is available from several sources in the US today. Nitrogen
generators filter relatively pure N2 from air and can be a very economical
source of Nitrogen. They can be built or used with a blending device and
a CO2 source to provide all the gas for any bar or facility.
What will mixed gas do?back to top
of page
What mixed gas does best is to leave beer the same. Strange as that sounds,
it means that used correctly, mixed gas will assure that the gas content
of the beer stays constant, never overcarbonating or going flat. In the
case of nitrogenated beers, (like Guinness) mixed gas keeps both N2 and
CO2 dissolved, and in the case of “normal” beers it means keeping
the CO2 content perfect.
“CO2 content” refers to how much CO2 is dissolved in the beer.
In the US we usually refer to it in “volumes”. One volume of
CO2 means there is exactly as much gas dissolved in the liquid as there
is liquid. For example, Coors has about 2.8 volumes of CO2. This means
that if you could get all the CO2 out of a half-barrel of beer and collect
it the gas would fill 2.8 half-barrel kegs.
CO2 is an ingredient in beer and affects flavor considerably.
It would be reasonable to compare CO2 to hops as a beer ingredient. Each
beer is “designed” with a CO2 content in mind, and to change
the gas content would change the flavor as surely as adding hops would.
A quick test of this would be to visit your nearest convenience store
and try the same brand of water in both still and carbonated versions.
The only difference you taste is the effect of the carbonation. Nitrogenated
beers generally have a very different flavor and one of the main differences
is caused by their much lower CO2 contents. Where Coors has 2.8 volumes
of CO2, Guinness has 1.2 volumes, less than half the CO2 of the Coors.
In comparing tastes, note the lack of sharpness or bite
in the lower CO2 content beer. Any product that was carbonated and loses
carbonation will have a new flavor and not a good one. To sample this
flavor, let the carbonated water mentioned earlier go flat and compare
the taste to that of the still water of the same brand. The difference
in flavors is the off-flavor left from carbonation gone flat. Beers that
go flat do not simply taste like lower CO2 beers; they have an undesirable
flavor.
CO2 Content also affects pourabilityback
to top of page
In a good draft system all beers can be poured properly as they come from
the brewery. Good brewers design beers to look good in the glass. If the
CO2 content of a beer goes up as it sits on draft the beer will become
foamy, taste too sharp, be hard to pour and be wasted. Waste of this type
can often be 6% to 8% of total beer sales. If the CO2 content of a beer
goes down while on draft the beer will taste off, look unappealing and
be wasted. Flat beer is wasteful because you are putting extra (poor quality)
beer in every glass. When this problem exists, waste can be 2% to 6% of
sales.
With over-carbonated and flat beers the problem increases the longer a
keg is on tap. With the trend toward having more beers on tap, each keg
is on tap for a longer time. Mixed gas is the perfect solution to these
situations. The correct blend(s) will keep all the beers at the right
CO2 content no matter how long they are on tap.
Bullet-Proof Systems
Draft beer systems that operate at higher pressures with the correct blend
of gas actually experience fewer problems with foaming and gas breakout.
The higher hydraulic pressures in the beer lines reduce the chance that
gas will break out, turning beer to foam. With pure CO2, these higher
pressures would eventually overcarbonate the beer. With a system designed
for these higher (20 – 30 psi) pressures and the correct blend of
gas you get the best of both worlds.
Premixed Bottles vs. Gas Blenders
You have two ways of getting mixed gas for dispensing beer. The most common
source of mixed gas today is high-pressure cylinders of premixed gas.
The second method is to mix N2 and CO2 using a blender on site. In most
cases, mixing gas on site is the lower cost and more practical option.
Premixed Cylinders are usually available in only one or two blends. While
it is possible to put any blend of gases in a cylinder, it is impractical
and more expensive to mix higher CO2 blends in a cylinder. When a cylinder
is used for pure CO2 or any blend containing more than 30% CO2 it is required
to be inspected every 5 years. Cylinders containing blends with 30% or
less CO2 can be inspected every 10 years. Also, cylinders with blends
of more than 30% CO2 cannot be filled to full capacity without affecting
the blend quality. The practical result is that blended gas is usually
available in blends of 25% CO2 (which is perfect for beers like Guinness)
or 30% which is the maximum practical CO2 percentage for premixed cylinders.
30% CO2 is not enough CO2 in the mix for normally carbonated American
beers. A 2.8 volume Coors would stay properly carbonated only if dispensed
at 380 F. and above 70 psi. In nearly all cases, a 50% to 80% CO2 blend
is appropriate for normally carbonated American beers.
Mixing gas on site using a gas blender allows the customer to buy N2 and
CO2 individually, which in most cases is far cheaper than buying mixed
gas in cylinders. Mixing on site also gives customers the chance to choose
the correct blend for their beers and their bar.
Why does the blend matter?back to top
of page
We all know that keeping the right pressure of CO2 on beer is required
to keep the beer right. Too much CO2 pressure and the beer will get foamy;
too little and the beer will go flat. The combination of blend and total
pressure determines the “partial pressure” of CO2 that the beer
sees. At 100% CO2 and12 psi the “partial pressure” of CO2 is
12 psi. At 18 psi and an 80% CO2 blend the “partial pressure”
of CO2 is still 12 psi and at 89 psi and a 30% CO2 blend the “partial
pressure” of CO2 is still 12 psi. It is the “partial pressure”
of CO2 that affects the beer’s carbonation.
Using 100% CO2 at 18 psi will eventually turn the beer into a 3.6 volume
beer, which would pour as pure foam. A blend of 30% CO2 at the same 18
psi would eventually cause this beer to have less than 1 volume of CO2,
one third of what the brewer intended. Since the pressure of an existing
system is already determined, we adjust the blend to keep the beer perfect.
Choosing the correct blend
CO2 is the critical element of the blend. We always recommend choosing
a blend that will keep the CO2 content of the beer constant. The second
gas (nitrogen) is only there to provide extra push as necessary. The math
of choosing a blend is a bit more than most beer service technicians will
want to contend with. All calculations must be done in absolute pressure
rather than the standard pressure we are used to. McDantim has made up
a slide rule that makes selecting blends straightforward.
These are available for FREE by contacting: McDantim,
Inc. toll free at (888) 735-5607 or by email at mcdantim@mcdantim.com.
What Mixed Gas won’t do!back to
top of page
Mixed gas is the perfect solution for maintaining CO2 content in draft
beer. This does not mean it will fix all evils or that the draft system
can be ignored or neglected. Mixed gas will never substitute for good
refrigeration, a good design or proper maintaince. As part of a good overall
package mixed gas will reduce headaches, improve your reputation and profits,
but it will not fix a bad draft system.
From the horses’ mouth
Garrett Oliver, Brewmaster for Brooklyn Brewery, recipient of the Institute
for Brewing Studies “Russell Schehrer Award for Innovation in Craft
Brewing” sums up the whole situation pretty well. He wrote recently,
“Over the last decade, many draught systems have begun to employ
pre-blended gas, ‘G-Mix’ to dispense beer. For many, G-Mix was
a great improvement over what they had been using – an air compressor
(air is one of beer’s worst enemies, and begins to destroy the product
immediately on contact, damaging flavor and causing it to go flat. Serving
your beer with air is the equivalent of pouring a pint, setting it down,
and then drinking it the next day). G-Mix is composed of 75% nitrogen
and 25% carbon dioxide. The selling point for G-Mix is that it will not
over-carbonate your beer. This is true. Unfortunately, it’s only
half the truth.
Instead, G-mix often makes your beer go flat, ruining the quality of your
beer, and costing you business and plenty of money. The ‘G’
in G-mix stands for ‘Guinness’. Guinness is a beer, which is
almost flat and needs to be served under very high pressure. The purpose
of G-mix is to keep Guinness from becoming over-carbonated or going completely
flat under high pressure. The problem is that G-mix has this effect on
all beers – they will become as flat as Guinness or flatter.”
Any draft beer system that uses too high a pressure to properly use pure
CO2 will benefit greatly from the correct blend of mixed gas. The right
blend will protect the quality of the beer, prevent or reduce foaming
or flat beer and save you and your customers’ money. Properly used,
it is and will continue to be one of the best tools in the draft technician’s
bag of tricks. Mixing on site with a gas blender is the most economical,
most convenient and best way to get the correct blend.
