HOPS FAQ, Revision 4, 08/04/94
Compiled/edited by Norm Pyle (npyle@hp7013.ecae.stortek.com)
This revision reviewed by Jeff Frane (gummitch@teleport.com) Q: What are hops?
A: Hops are cultivated flowers (humulus lupulus) used for preservative and flavoring
characteristics in beer. The bitterness of the hop is used to balance the sweetness
of the malt, and the essential oils add a flavor/aroma which cannot be achieved
by using any other plant. The hop plant is a perennial spiraling bine which
will grow in almost any climate given enough water and sunlight. It can climb
either string or poles and can reach heights of 40 feet. The flowers (or cones
as they are often called) are usually dried before use.
Essential Oils
Hops bring a lot more to beer than bitterness. The volatile oils, usually 0.5
- 3.0% (vol/wt) of the hop cone, are an important flavor component of many types
of beer. Brewers seeking to maximize hop flavor and aroma generally make late
kettle additions (0-15 min. before cooling) with high quality "aroma"
hops. Dry hopping, i.e. the addition of hops to the secondary fermenter or serving
tank, is another way to add hop character to a beer although the aroma components
retained by this method differ from those obtained in late kettle additions.
Q: Should I use pellets, or plugs, or loose hops?
A: Much has been written about what form of hops should be used. Loose hops
are just that: loose cones which have been dried after picking. Plugs are loose
hops which have been subsequently pressed into a bung under pressure, generally
in 0.5 oz. sizes. Pellets are loose hops which have been ground to a fine powder
and then pressed into rabbit-food-sized pellets.
LOOSE HOPS
Advantages: They are the most natural form of the ingredient. They float, which
is good for siphoning out from under, and form a natural filter bed. When they
are fresh, they beat all others in terms of aromatic hop oils.
Disadvantages: Since they are loose, exposure to air (oxygen) is the greatest
and they can lose quality more quickly than the other forms of hops. When stored
in vacuum-sealed or CO2 or nitrogen purged Oxygen barrier bags or jars, this
problem can be avoided. They are bulkier than other forms.
PLUGS
Advantages: Are nearly the same as loose hops, in that, when hydrated, they
become whole hop cones again. Like loose hops, they float. They may be better
protected from air, but this is unproven.
Disadvantages: Few hop varieties come in this form. It is difficult, but not
impossible to separate into increments smaller than 0.5 oz. The compression
of the hops into this form causes the lupulin glands to burst, which causes
a finite loss of the volatile hop aromatic compounds.
PELLETS
Advantages: Convenient to measure and may have better protection from air (another
unproven assumption). They sink, so they get maximum contact in a still wort,
as when used for dry hopping (may or may not be an advantage). If they are subsequently
covered with dead yeast, wort contact is mostly lost, so careful timing is recommended
when using them for dry hopping. They reportedly contribute 10% more alpha acids
to the wort because of maximized surface area, so are a more efficient use of
this relatively expensive ingredient. They are generally available in more varieties.
Disadvantages: They sink and are powdered, so it is difficult to avoid them
when siphoning. The extra processing of chopping and compressing negatively
affects hop aromatics.
Given the pros and cons listed, the choice of which form of hop to use in a
certain application is up to the individual brewer and dependent upon the individual
brewhouse.
Q: What are AAU, HBU, and IBU's?
A: Alpha Acid Units (AAU) and Homebrew Bittering Units (HBU) are the same. For
the sake of discussion we will use the term AAU, which is calculated as follows:
AAU = AA * W where AA = alpha acid % provided with the hops
W = weight of the hops in ounces
It is generally assumed that, when using AAU or HBU, the batch size is the standard
homebrewing unit of 5 gallons. Another drawback to using AAU's is that they
don't consider the utilization obtained from long, intermediate, or short boil
times. Fudge factors are sometimes added but at best they offer a rough approximation.
To help solve these problems, the International Bittering Unit (IBU) may be
used. With it, the brewer can get a more accurate (though admittedly still rough)
approximation of the bitterness given up by a given quantity of a given AA hop
for a given boil time. Actual IBUs can be measured in a laboratory, but the
average homebrewer has no access to such equipment.
Q: How do I store my hops?
A: At as low a temperature as possible, likely to be in your freezer. Also,
attempt to remove as much air as possible from the package and use airtight,
preferably oxygen-barrier packages.
Q: What is dry-hopping? How do I do it? How much do I use? What variety? What
form of hops?
A: Dry hopping can be defined as adding hops to a cooled wort at sometime during
the fermentation process. It adds a fresh hops aroma/flavor to the beer which
cannot be matched with hop additions into hot wort. It is not to be confused
with finish/aroma hopping, which is done on the hot wort while still in the
kettle. The best time to dry hop is after primary fermentation has slowed and
little CO2 is being driven off the wort. Dry hopping earlier than this point
is inefficient as the volatile hop oils are scrubbed away by the exiting CO2.
The proper length of time for dry hopping is dependent on the temperature. At
ale temperatures, 7-14 days of contact time is widely used. At lager temperatures,
although little data is available as few lagers are dry hopped, it seems obvious
that longer contact times, on the order of 14-21 days, are called for. It is
common to use 0.5 - 2.0 oz. or more in a 5 gallon batch, but as always it is
up to the individual's preferences and the hop variety.
The rare commercial brewer that dry hops generally leaves the hops on the beer
for a longer time than the average, impatient homebrewer. This is undoubtedly
to extract more aroma from this relatively expensive ingredient.