This is the fourth revision of this document. There are no major changes from revision three, I've just attempted to clarify some things. I've also added more opinions (mine and others) because as I research this subject, I find that facts are not nearly as abundant as opinions ;-). Actually, opinions and personal experiences are about as good as you can get when referring to enigmatical concepts such as aroma and taste. Hard science this is not. I have not credited each passage individually, as the original sources were sometimes confused with persons just passing on the information. Also, some editing has been done, so that some of the information is changed from the originals. I have made every attempt to credit people who have helped this effort in any way, but it is possible that someone was missed. Note also that some email addresses may be out of date, but that is way beyond my control. If you have contributed to this FAQ, and do not see the appropriate credit, please contact me directly. No offense is intended.
The following general topics are presented in this FAQ:
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 vine 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.
Q: What are the compounds which provide the bittering? What about the aroma compounds?
A: Read on:
One of the major contributions hops give to beer is a characteristic bitterness that provides a counterpoint to the rich sweetness provided by the malt. This bitter flavor is extracted from the hops during the boil. It is during this time that virtually insoluble alpha acids are isomerized (rearranged without changing their composition) into more soluble and stable iso-alpha acids, the main bittering substance in beer. Five different naturally occurring alpha acids have been isolated from hops which are:
humulone cohumulone adhumulone prehumulone posthumulone
Although isomerized alpha acids are the biggest contributers, hops contain beta acids which also add bitterness to beer. The beta acids are similar to alpha acids both in structure and abundance. In contrast to alpha acids, it is not isomerized beta acids that add bitterness, it is the oxidation products of the beta acids, which are bitter and soluble, that make their presence felt. It should be noted that oxidized beta acids are not as bitter as isomerized alpha acids.
Both the alpha and beta acids are very susceptible to oxidation, especially at temperatures above freezing. Theoretical losses of alpha acids of up to 60% have been calculated for hops which are packaged and stored poorly. This is important because once alpha acids have been oxidized they can no longer be isomerized into iso-alpha acid, thus decreasing the hop's bittering potential. As stated above, oxidation components of beta acids contribute to bitterness, thus the bittering potential of oxidized hops may not decrease as much as is commonly thought. This does not, in any way, argue against storing hops well, since essential oils are dramatically and negatively altered by oxidation.
For these reasons, the "storageability" of each hop variety is sometimes provided, along with the alpha and beta acid levels, by the hop broker. This parameter is usually given as a percentage of the alpha acids present after 6 months at 20C. Some good storage hops (usually high alpha acid) lose only 15-20% of their alpha acids: Cluster, and Galena are among the best. Most high quality aroma hops lose anywhere from 35-65% of their alpha acids unless anaerobic conditions and cold storage (< 0C) are provided. This is why it is imperative for brewers to buy the freshest hops available and store them in the coldest environment available, usually the freezer. It is also important to package the hops properly, which means removing as much oxygen as possible and containing them in an oxygen barrier material.
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. The maximum oil utilization is about 10 - 15% which decreases with increased boiling time.
The essential oils are what give hops their unique aroma; each variety has its own distinct profile. The smell of hops freshly crushed in your hand is quite often different than that in a finished beer. This is due to the fact that the major components in hop oil, beta-pinene, myrcene, beta- caryophyllene, farnesene and alpha-humulene, are not usually found in beer. However, fermentation and oxidation products of these compounds, especially humulene epoxides and diepoxides are considered contributors to "hoppy" flavors and aroma. The exception here is with dry-hopping, where some of the hop oil components do survive into the beer intact.
Researchers have not been able to duplicate the complexities of hoppy character by adding pure chemicals in any proportion or combination. Consensus is that there is a synergistic blend of several compounds, some of which may have not yet been discovered.
Hop researchers, using capillary gas chromatography, have detected and identified more than 250 essential oil components in hops. Twenty two of these have been pinpointed as being good indicators of hoppiness potential. They are subdivided into 3 groups, humulene and caryophyllene oxidative products, floral/estery compounds, and citrus/piney compounds, as listed below:
caryolan-1-ol caryophyllene oxide humulene diepoxide a humulene diepoxide b humulene diepoxide c humulene epoxide I humulene epoxide II humulene epoxide III humulenol II humulol
geraniol geranyl acetate geranyl isobutyrate linalool
delta-cadinene gamma-cadinene citral limonene limonene-10-ol alpha-muurolene nerol beta-selenene
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.
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: They float, so some contact with a still wort (as in dry hopping) is thought to be lost; this disadvantage is certainly arguable though, especially when it is considered that by using weighted hop bags, it is a non-issue. 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.
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. Currently, any domestic varieties are first shipped to England where they are made into plugs and then shipped back to the U.S. This probably negates any potential freshness advantage they have over loose hops (for U.S. varieties). 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.
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 upong the individual brewhouse. With some kettle arrangements (those using a hopback, for instance) loose hops can form a utilitarian filter bed. In others, the mass of loose hops can be a nuisance and soak up a large quantity of wort which is lost to the brewer. It should be noted that fresh, whole hops are available today from many sources, including mail-order nationwide (US) from companies such as Freshops, HopTech, HopUnion, and The Hop Source, which may negate many of the advantages of processed hops.
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
AAU's are literally hundredths of an ounce, so the units would be ounces. This is a bit awkward, and they are usually discussed as if they are "unit-less". It is generally assumed that, when using AAU or HBU, the batch size is the standard homebrewing unit of 5 gallons. If a beer is said to have 10 AAU's of bitterness in it, and it is a 5 gallon batch, there would probably be no confusion. On the other hand, if it is a 10 gallon batch, there is actually half the AAU's per gallon when compared to the 5 gallon batch and the beer would be quite different. 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. It is independent of batch size so that a 5 gallon batch with 29 IBU's has the same bitterness as a 50 barrel batch with 29 IBU's. The equations are commonly quoted from Jackie Rager's article in the Zymurgy Hops and Beer Special Edition published in 1990. Revised numbers have recently been presented by Glenn Tinseth and Mark Garetz, in separate works, which is good in terms of providing better data. On the other hand, the additional data makes comparison's more difficult. Now, if a beer is said to have 30 estimated IBUs, it cannot be assumed that the Rager numbers were used. Note also that these are estimates. Actual IBUs can be measured in a laboratory, but the average homebrewer has no access to such equipment. The tables and formulae follow:
Boiling Time (minutes) %Util (Rager) %Util (Tinseth) %Util (Garetz-Avg Yeast) ---------------------- ------------- --------------- ------------------------ less than 5 5.0 5 0 6 - 10 6.0 5 0 11 - 15 8.0 8 1 16 - 20 10.1 10 4 21 - 25 12.1 12 6 26 - 30 15.3 15 11 31 - 35 18.8 19 13 36 - 40 22.8 23 19 41 - 45 26.9 24 23 46 - 50 28.1 25 24 51 - 60 30.0 26 25
It has been reported that since iso-alpha acids possess a slight electrical charge, they can be lost in many ways. Among these are absorption into the yeast cell walls (and subsequent removal of the yeast), attachment to coagulating proteins (and subsequent removal of this trub), attachment to filters, etc. It is unclear if Mr. Rager's utilization numbers have assumed these losses, but it can be assumed that Tinseth and Garetz did take them into account. The Garetz numbers represent average yeast flocculation; he also provides tables which represent fast and slow yeast flocculation. Finally, note that the new book published in 1994 by Mark Garetz has not been reviewed for this FAQ. Early reviews are positive, and it is said to contain lots of new and debatable information regarding hop utilization.
Utilization can be reduced to a smooth function, as opposed to the tables, which produce many discontinuous lines. The Rager table is presented in the following utilization equation:
%UTILIZATION = 18.11 + 13.86 * hyptan[(MINUTES - 31.32) / 18.27]
Continuing with Jackie Rager's method...
If the gravity of the boil exceeds 1.050: ADJUSTMENT = 1 + ((BOIL_GRAVITY - 1.050) / 0.2) otherwise, ADJUSTMENT = 1
This adjustment is used by placing it in the denominator, i.e. the volume gets multiplied by this adjustment.
IBU_PER_GRAM = (%UTILIZATION * %ALPHA * 1000) / VOLUME(litres) IBU = GRAMS * IBU_PER_GRAM To predict the number of ounces needed to hit a target IBU: GRAMS = IBU / IBU_PER_GRAM
IBU_PER_OZ = (%UTILIZATION * %ALPHA * 7462) / VOLUME(gallons) IBU = OUNCES * IBU_PER_OZ To predict the number of ounces needed to hit a target IBU: OUNCES = IBU / IBU_PER_OZ
Jackie Rager's numbers have been used successfully by hundreds of homebrewers and provide a consistent base with which to work. It is apparent that his constant 7462, derived from metric to US conversion, is actually closer to 7490. The ADJUSTMENT factor could be questioned as well, as it is intuitively obvious that a gravity of 1.049 does not affect utilization exactly the same as a gravity of 1.000 (water). It is assumed (but not verified) that the utilization table is corrected for this assumption and/or the difference is small enough that it has little effect on the final bitterness of the beer.
Note also that Mr. Rager's numbers are often used for pellet hops thrown loose in the boil. Al Korzonas suggests adding 10% more hops if used in a hop bag, and 10% more than that if loose hops or plugs are used. Glenn Tinseth notes that his table is "closer to reality" than Rager's, when using fresh whole cones loose in the boil. Mr. Tinseth also offers the following utilization adjustment for OG > 1.040 and boil times > 15 minutes:
%UTILIZATION = %Base_Util(From Table) - ((OG - 1.040) * 100)
This value would be used in the above formulae to adjust for reduced utilization based on boil gravity.
It should be obvious that the alpha acid utilization is a widely debated topic, and that it is not an exact science. Homebrewing systems vary so widely that it is impossible to be very accurate with the IBU estimates. The homebrewer who strives to be accurate within 10% of actual can probably achieve it, and verify it with known commercial examples. The human tongue is accurate enough for this delightful experiment. Precision with IBUs is certainly achievable, with careful record-keeping, including personal sensory descriptions, and the use of a consistent set of formulae and utilization tables. These steps will go a long way toward consistent quality beer.
Q: How many IBUs should I shoot for in a beer with XXX original gravity?
A: The AHA and probably other organizations publish (large) charts which define the range of IBUs expected in a given style. It is outside the scope of this FAQ to go into that much detail on beer styles. The following table from an article titled "Matching Hops with Beer Styles" by Quentin B. Smith in the 1990 Zymurgy Hops and Beer Special Issue may help. The beer style has much more to say about what the goal IBUs should be for a given beer, but this is a starting point (not a GOOD starting point, but A starting point):
Balanced Beer Hop Chart Wort OG IBU ------- --- 1.010 4 1.020 8 1.030 12 1.040 16 1.050 24 1.060 32 1.070 40 1.080 48 1.090 56 1.100 64
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: Can I grow my own hops? How?
A: Read this...
Hops for beer-making grow from the rhizomes of female hop plants. Rhizomes look like root cuttings but have buds growing from them that will become new vines. Rhizomes also contain stored nutrients to support initial growth.
Hops grow vertically as one or more vines that spiral up a twine or other support. Depending on latitude, location, and variety, they sprout from March or April and grow through the summer and early fall. A single plant can easily grow 40 feet tall when it is mature but growth in the first year is usually much less. In most instances by the second or third year the plants will exhibit full growth. Height is very closely linked to the amount of sunshine the plant gets.
Hops grow best in full sun and you should pick a spot with the best possible southern exposure. Hops grow best in loose, well drained soil. Blended peat moss and sand make a good growing environment. In cases of poor soil drainage, it can be helpful to create a mound of soil a foot or so tall which will aid drainage.
Hops need lots of water. As they grow be sure to give them a very good soaking at least once a week. There are reports that once-a-day waterings (up to 6.5 gallons per mound) give greater growth and yield. Mulch in the summer helps with weed control and also holds water. Hops also have big appetites; composted cow manure is an excellent well-balanced fertilizer for them.
Once a bed has been prepared the rhizomes are planted about 4 inches below the soil surface with any obvious buds coming from the rhizome oriented to point upward.
After several inches the new vines can be thinned so that just the most healthy and vigorous three vines are left to continue growing. This will be an ongoing process as new shoots may show up later, but the initial thinning is thought to be important by some home hop growers. It's been reported that the young shoots that are culled may be steamed and eaten like asparagus. On the other hand, some growers espouse cutting the new shoots at all, allowing all vines to grow to full height.
As the vines grow over a foot tall they should be trained to grow up a twine. This can be done by twisting the vine around the line. This may have to be repeated for a few days before the vine gets the idea. Hops will have a natural tendency to wrap clockwise looking down.
The most common hops trellis consists of strings running from the roof of a building down to stakes driven into the soil near the plants. Another option, often used by commercial growers, consists of a large central pole, with strings running from the top of the pole down to the foot of each plant, similar to the spokes on a wheel. Expect the string or twine to hold a lot of weight as the vines grow tall. A 25+ foot plant may weigh 20+ pounds.
Hop blossoms start out looking like large sand burrs, and then take on a characteristic cone shape as they grow in size. The size of a fully developed cone depends on the variety, varying from 1 to 2 inches long by 1/2 to 1 inch in diameter.
The hops are fully mature and ready for picking when two changes take place. First, immature hops have a damp, soft feel and when squeezed slightly tend to stay compressed. Mature hops feel more like paper, spring back when squeezed, and feel noticeably lighter. The second key test is to pick an average example hop and cut it lengthwise down the center with a knife. When ready to pick, the yellow powder (the lupulin sacs containing the essential oils and bitter compounds) will be a dark shade of yellow, like the stripes on a highway, and it will be pungent. If a light shade of yellow then its likely the hops are immature.
When ready to pick it is best to snip the stems of the cones with scissors or a knife to avoid jarring the hops and knocking lupulin powder out or worse, pulling the center of the cone out with the stem, causing a great loss of lupulin. Touching hops plants can cause skin irritation in some people; gloves and long sleeves can help in this matter.
Just-picked hops are roughly 80 percent water; if left alone they spoil rapidly. For proper storage most of the water is removed by drying. A good drying method is to lie the hops on a card or screen in an attic. Just a few hours during the heat of summer or a few hours more in cooler weather is enough to dry the hops. Use a before and after weighing (and trial and error) to try to achieve about 7-10 percent residual moisture after drying.
After drying, hops keep best at low temperatures and away from oxygen. A kitchen freezer easily takes care of temperature but to get the hops away from oxygen is difficult. Tightly packing hops in canning jars will minimize the trapped air but be careful not to use too much force and break the all important lupulin sacs since this accelerates oxidation. Purging the canning jar of oxygen by blowing in carbon dioxide from a kegging system will also help prolong freshness.
It's common to get 4 or 5 harvests per year by picking the biggest, most mature hops every 2 weeks or so as the flowers ripen. Patience and judgement are important since cones left on the vine too long turn brown and begin to oxidize and spoil, while immature hops have little lupulin to give.
At the end of the growing season when the leaves have fallen or turned brown, cut the vines at the surface of the soil and if possible remove the twine. After cutting back the vines a layer of 3 or 4 inches of mulch and composted manure can be put over the exposed vines for insulation and nutrition during the winter.
Japanese beetles are the number one nuisance in many areas. A common remedy is to position a "Bag a Bug" type beetle trap about 30 feet directly up wind from the hop vines. There is some concern that the "Bag a Bug" traps may actually attract more beetles than they catch, but that probably depends on the situation. Certain plants such as rose bushes may also attract the beetles, so it's best to keep those plants away from your hops. Also, the beetles' larvae live in the ground, and in cases of extreme Japanese Beetle infestation the surrounding lawn may need to be treated accordingly. A number of other pests, such as aphids, can harm hops, and can be treated with any number of pesticides. Since you will be consuming these hops, you should use low toxicity natural pesticides, such as 1% Rotenone dust, for direct pest control on the plants. As with any consumable, you should ensure that any pesticide is well washed before using the hops.
Ladybugs are the best, most natural way to get rid of aphids and a lot of other bugs. However, it can be difficult to keep them on your hop plants once you run out of food for them. A good idea is to plant some cilantro/coriander between your hop hills. Ladybugs are attracted to this plant and it will keep their attention between feedings of aphids. You can even harvest the cilantro (the leaves) for cooking and use the coriander (the seeds) in Witbier.
One other hazard is animals. A short fence of rabbit wire will keep cats, dogs, rabbits, etc. at bay, but won't do much against deer.
Rhizomes are available from an increasing number of sources. American Brewmaster in Raleigh, NC, Freshops in Philomath, OR, and The Hop Source in Silverton, OR, are all well-known suppliers. Cost is usually a few dollars each. They should be kept in plastic bags, moist and cold in your refrigerator until they are planted.
Additional information about hop growing can be found in "Homegrown Hops" by David R. Beach. Also, the 1990 Zymurgy Hops and Beer Special Issue is devoted to hops and contains an article about growing hops by Pierre Rajotte. The AHA also has additional hops-oriented publications.
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 can be thought of as "cold-hopping" or "raw-hopping", as these hops do not "cook" like the kettle hops. 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 use of a hop-back, where hot wort is passed through the hops, is another form of finish hopping; it is not dry hopping. Dry hopping gives no alpha acids to the wort, but it may contribute some oxidized beta acids; its bittering contribution to the final product is very small. It is more likely to add a perceived bitterness with the addition of the intense aroma rather than an actual bitterness due to bitter acids.
There are several ways to dry hop, if one considers the variations of making hop teas, etc. 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. Also, dry hopping early in the fermentation phase may result in hops on the bottom of the fermenter being covered with yeast, which results in inefficient extraction of aroma. Another consideration of timing dry hopping is with infection risk. Hops in contact with boiling wort are effectively sanitized. Addition of dry hops after primary fermentation allows them to contact a wort/beer with some alcohol and less sugars, which prevents infections from getting a foothold.
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.
Fuggles, Northern Brewer, Saaz, Cascade, all Hallertauer variants, and many other hops have been used successfully. It should be noted that the aroma of the beer greatly influences the profile, and that the "correct" aroma hop should be used to match the style (i.e. English hops for English ales). American brewers have traditionally used hops from all over the globe so European hops, for example, can be used without fear of an terrible mismatch. Note also that traditionally, German beers are not dry-hopped but that American versions of German styles are sometimes dry hopped.
The first and foremost way to dry hop is to simply put the hops into the fermenter. The most common worry with this method is about infecting a beer which is nearly ready to bottle/keg. Hops are natural preservatives, and infections from this method are very rare. Of course, an infection source in a homebrewery is impossible to prove, but this risk is certainly minimal. If loose hops or plugs are used, they will float, and many brewers use a sanitized hop bag and marbles to sink the hops for maximum contact. If pellets are used they will sink, but may be difficult to avoid when bottling or kegging. Also, the pellet hops can be easily covered by yeast falling out of suspension, so they should be added after virtually all fermentation activity has ceased, and a good amount of the yeast has fallen. Finally, it is worth mentioning that pellets are not well regarded for dry hopping because the pelletization process is very rough on the volatile aromatic compounds which the brewer is attempting to capture.
Another method used to dry hop is to steep the hops in a white alcohol (grain, vodka, etc.) and sometimes water solution for hours or days, then pour this solution into the fermenter. This is a common practice among those who want to protect against the remote possibility of infection with normal dry hopping. It should be noted that as the temperature of the alcohol/water/hops mixture is raised, the effect approaches that of finish hopping, as the most volatile hop oils are driven off.
Adding hop oil, a product recently introduced to the homebrewing market, is another way of "dry-hopping". It should be done after primary fermentation has slowed for many of the same reasons.
These dry hopping methods, and others, will produce different results, mainly because the desired compounds are so volatile. The variety of reactions taking place during processing and fermentation will affect the results. The "best" method is the one which gives the desired result to the individual homebrewer.
A final note about dry-hopping: the volatile hop compounds will react quickly with oxygen. For this reason, extra measures should be taken to avoid mixing with air during bottling or kegging, in order to retain the hop aroma for extended periods of time. These extra measures may include purging the bottling vessel and keg with CO2, very quiet siphoning, oxygen scavenging caps, and possibly delayed capping after bottling. This method allows any CO2 coming out of solution during the bottling process to push the oxygen out of the bottle before the caps are secured. This method is used by many homebrewers but, as always, the results are inconclusive. The simplest method is to use the oxygen scavenging caps, which requires no extra effort and little extra cost. For further reference, the Summer 1993 Zymurgy contains an article by Mark Garetz on this subject.
Q: What is a "hop-back"? How is it used?
A: A homebrewer's hop-back is a reservoir connected in-line between the kettle and counter-flow chiller. It is filled with fresh hops before the flow is started. The hot wort flows through the fresh hops and is quickly chilled by the counter-flow before entering the fermenter. Many of the volatile hop aroma compounds are extracted and brought into the fermenter with this process. It is generally thought to produce a flavor/aroma profile somewhere between late kettle additions and dry-hopping. A good article on building a hop-back by Kinney Baughman is in the Zymurgy Gadgets and Equipment Special Issue. Another good article on a hop-back, written by Charlie Stackhouse is in the Fall 1994 Zymurgy edition.
Q: Can I use fresh hops rather than dried hops? How much do I use?
A: Yes, you can but at best it is a rough guess as to how much. The rule of thumb is to use 6 times as much (by weight) as you would dry hops. A safer rule would be to do this and to only use them for finish/dry hopping. Since these hops have not been tested, the AA% is unknown, and later additions are less sensitive to AA%. It should be noted that some homebrewers have had mixed results when using fresh hops (poor AA approximation for bittering, sometimes grassy aroma for finishing).
Q: If I use an equal number of HBUs (or IBUs) for bittering a beer with a high alpha hop and a low alpha hop, will the beers taste the same?
A: The short answer is: probably not. The longer answer has to do with the oils in the hops. As previously stated, hops bring much more to beer than bittering. There are different qualities of bittering and many respected brewers agree that a cleaner, smoother bitter can be attained by using an equal number of IBUs from a low alpha hop. To quote George Fix: "I have always had a strong preference for low alpha aroma hops, even for early additions for bittering. I find that they give (if fresh!) a clean and mellow bitter, which contrasts with the crude effects I pick up from high alphas." The ratio humulene/myrcene has been mentioned with respect to this, with higher ratios (> 1.5) being considered good. As in all areas where human perception is involved, proof is difficult.
Q: What varieties of hops are available to the homebrewer? Where are they grown? What do they taste/smell like? Who uses them in commercial beers? How much bitterness do they contribute? How do I use them? What are good substitutes?
A: The following table lists many common hop varieties available to the homebrewer:
DISCLAIMER: Hop substitutes should generally be thought of as "last resort" options. Some of them work better than others, and of course, the individual brewer must decide which substitutes are best. No attempt was made here to label "good" and "not-so-good" substitutes, because the opinions vary wildly.
The following hops are generally considered aroma hops although in recent years they have started to gain a following in the homebrew community for bittering as well:
Glenn Anderson (firstname.lastname@example.org)
Scott Barrett (adiron!partech.com!scott@uunet.UU.NET)
Jeremy Bergsman (jeremybb@leland.Stanford.EDU)
Jim Busch (email@example.com)
Nick Cuccia (Nick_Cuccia@talamasca.berkeley.ca.us)
John DeCarlo (firstname.lastname@example.org)
Alan Edwards (email@example.com)
George Fix (firstname.lastname@example.org)
Bill Flowers (email@example.com)
Jeff Frane (firstname.lastname@example.org)
Mark Garetz (email@example.com)
Russ Gelinas (R_GELINAS@UNHH.UNH.EDU)
Al Korzonas (firstname.lastname@example.org)
Rick Larson (email@example.com)
Don Leonard (firstname.lastname@example.org)
John Palmer (email@example.com)
Bob Regent (firstname.lastname@example.org)
Peter Soper (?)
Spencer Thomas (email@example.com)
Glenn Tinseth (firstname.lastname@example.org)
Rich Webb (email@example.com)
Patrick Weix (firstname.lastname@example.org)
Carl West (eisen@kopf.HQ.Ileaf.COM)
Ed Westemeier (email@example.com)
Dave Wiley (firstname.lastname@example.org)
Gene Zimmerman (EZIMMERM@UWYO.EDU)