What Red Green didn't Know About Hops
By Mark Tumarkin
What are hops? I remember watching a Red Green episode in which Red was trying to turn an old washing machine into a mini-brewery. Ya gotta love it. At any rate, despite the fact that he felt himself to be a beer expert (having consumed vast quantities), he had no idea what a hop was. Even his consultants (the rest of the Possum Lodge members) were no help. Someone remembered from a brewery tour that hops were small pellets. Through some impressive deductive reasoning, Red concluded that since rabbits hopped and rabbit food was small green pellets, rabbit food must be hops. Rabbit pellets were easily available and he was on his way to beer heaven; though since this was the Red Green Show, there were a few other small stumbling blocks along the way.
We know that hops are the cone-shaped flowers of Humulus lupulus, a vining plant that is a member of the Cannabis family, a cousin of our old friend marijuana. Though Red's friend Buzz Sherwood, the burned out American hippie pilot, neglected to point this out to Red or the episode might have taken a different twist. Hops are used in brewing to balance the malty sweetness of beer. Before hops became commonly used, many different herbs and plants were used for this purpose. Collectively, these were called gruit. In addition to providing a balancing bitterness, many of these plant materials had medicinal or psychotropic properties.
Hops are indigenous to many parts of the world. North America, Europe (including England), and Asia all have their own unique native species. Just when hop use became prevalent in Europe is unclear. The first written records indicate that monasteries in the Hallertauer region of Germany were growing hops as early as 736 AD. Brewing references commonly state that hops were in accepted use in most of Europe by the late 1500's to mid 1600's. Though, as Mark Garetz points out in his book Using Hops, the Reinheitsgebot dates to 1516 and requires the use of hops by law. Hops certainly had to be widely used and accepted for some time prior to this before their use would be legislated by law.
In addition to bittering the beer, hops also have anti-microbial properties. This provides a preservative quality to the beer. Long before our modern understanding of yeast and sanitation practices, hops were used to allow beer to be kept for longer periods of time. Hopping rates were generally much higher than today because of these preservative effects. Beer brewed for immediate consumption was probably hopped much like our homebrews today, while beer brewed to be stored (often called Stock Ale) was hopped at a much higher rate. India Pale Ale, which had to survive a 5-6 month sea voyage through tropical climes, was probably the epitome of hoppage, being bittered to Dr. Bob levels. Keep in mind that high hop rates not only protected the beer, but also helped cover up any off-flavors. Thanks to Fred's educational talk at our recent meeting; we now know that Burton-on-Trent was the home of the IPA brewers, not a British gay porn novel. It's probable that hops were first used to provide bitterness and that the preservative qualities were discovered later as an added benefit. Other benefits of boiling hops in our wort is that they lower the surface tension of the water (allowing us to more easily maintain a vigorous boil) and their tannins help form a good hot-break by combining with the unwanted proteins, thus contributing to a clearer beer.
Although arguably the most important contribution of hops, bittering is just one of the ways hops affects beer character. In addition to bittering, hops affect beer flavor and aroma as well. In order to understand these contributions, we need to look at the mechanics of how hops affect our beer. The hops contain a number of compounds that come into play. These compounds, mainly hop resins (alpha and beta acids) and oils, are contained in the lupulin glands at the base of the leaf like structures of the cones, or female flowers. For bittering, we are primarily concerned with the alpha acids. There are many of these compounds but the most important are humulone, cohumulone and adhumulone. The levels of these acids vary with the particular hop variety. A high cohumulone content is thought to produce a harsher character in the bittering. These alpha acids are easily soluble in wort at high temperature. However, they don't bind with the other wort components and will drop out of solution once the beer is cooled, thus loosing the bittering qualities. Luckily, a long and vigorous boil causes the compounds to go through a chemical change known as isomerization, which rearranges the molecules into iso-alpha acids which remain soluble in wort and allow a more permanent bittering. Even so, hop character will fade over time with long storage.
The beta acids are not thought to be as directly important to bittering. However, they do oxidize to more soluble components as the hops age. The alpha/beta content ratio is important as a quality indicator. The essential oils are a more important contributor to hop character, particularly hop aroma and flavor. These oils are very complex, including components containing hydrogen, oxygen and sulpher. The hydrogen compounds (like humulene and mercene) and the oxygen compounds (like linalool and geraniol) are the most desirable to capture in our beer. Most of the sulpher compounds are driven off in the kilning process. These are the compounds that are responsible for the skunking process when beer is exposed to light or heat. A key factor to keep in mind is that hop oils are very volatile. They can be easily driven off in the boil.
This leads us to how we get the hop character into our beer. Hops are added at three possible stages during the boil; these are called the bittering, flavor, and aroma additions. The bittering, or kettle hops, are added at the beginning of the boil as a vigorous boil of at least 45 minutes (and preferably 60-90 minutes) is needed to allow for the isomerization of the alpha acids. Since the hop oils responsible for flavor and aroma are volatile, flavor additions are made in the last 15 minutes (more typically the last 5-10 minutes) of the boil, while aroma additions are made at knock-out (when the burner is turned off). Some brewers use a hop-back or hop-jack for additional aroma contributions. The hop-back is a container that holds hop leaves and filters the wort on its' way to the fermenter during the cooling process. Another method for adding hop aroma is dry hopping (or what used to be called raw hopping). Additional hops are put in the fermenter (after the primary, vigorous fermentation is finished so that the hop oils aren't scrubbed from the green beer by escaping CO2) or into the keg during the finishing and conditioning period.
These are the most common practices, though other processes such as first wort hopping and mash hopping are gaining more acceptance recently. Actually, these are both old traditional processes that are regaining their place in modern brewing practices. First wort hopping is the practice of placing your flavor and aroma additions into the kettle as you finish your sparging process so that they are in the kettle as the wort collects and before the boil begins. Mash hopping, as you'd imagine, puts hops into the mash itself. These processes are believed to achieve a more refined flavor and aroma from the hops than more traditional boil methods.
Based on the above methods, hops are commonly divided into two main categories; bittering and aroma hops. There are hops which have characteristics of both categories and are called dual purpose hops. Typically, bittering hops are varieties that have a high alpha acid content, usually twice (or even more) that of the aroma varieties. Alpha acid is stated by percentage. Traditional aroma hops have alpha ratings of 5% or less, while bittering hops can range between 5-10% or higher. New varieties with alpha content above 10% are often called super alpha hops. Some of the oldest European aroma hops are considered to be the most desirable varieties and are called Noble hops. These include Hallertauer, Tettnanger, Saaz, and Spalter. These noble hops are also used for bittering in the finest lagers. Some examples of commonly used bittering hops would be Centennial, Perle, and Brewer's Gold. Examples of popular aroma hops would include Cascade, Goldings, Fuggles, and Willamette. Some dual purpose hops would include Northern Brewer, Cluster, and Centennial. Super-alpha hops would include Chinook, Galena, and Nugget.
One thing to keep in mind is that industry needs drive hop breeding programs. The needs of the brewing industry are foremost, but agricultural factors also play a large part. Hops are a crop and farmers must turn a profit. Thus, factors like disease resistance (against powdery and downy mildew, spider mites, etc) and high yield per acre are crucial. Storability is another factor. Alpha acid and volatile oils degrade over time, even while hops are kept in cold storage. Current breeding programs seek to produce new varieties that combine disease resistance, high yield, and good storability in high alpha (often super alpha) hops that are dual purpose and can be used for both bittering and flavor/aroma additions. Some new examples are Sterling (a cross of Saaz/Cascade/Brewers Gold, 7% alpha, which combines the herbal spiciness of Saaz with the Citrus character of Cascade) and Simcoe (a very floral, high alpha hop of 15 % which is a cross of Cascade and Chinook).
We also want to look at the various forms in which hops are available. The two most common forms are whole or leaf hops (though often called leaf hops, they are really the cones, or female flowers) and pellets. The pellets are made by grinding whole hops and then compressing them into small pellets (remember Red Greens' misunderstanding?). There are several forms of pellets, but the most common is called the Type 90 pellet. A third and intermediate form is hop plugs. Plugs (or Type 100 pellets) are simply whole hops that have been compressed into ¸ oz cylinders. Once the plugs are put into the boiling wort, they return to their original form. Another form is Iso-alpha acid or super-critical extract. These hop oil extracts are generally not of concern to the home or craft brewer, although they are available if you wish to experiment. Miller claims that their use of specially treated hop extract prevents skunking, despite the clear glass bottles they use, to which I reply - who cares? The beer still sucks. But I digress. Each type has its advantages and disadvantages. Some of the factors to consider are utilization, system issues (possible plugging problem with pellets), degradation over time, etc. Whole hops don't have the plugging problems that are possible with pellets. In fact, they provide an excellent filter bed, useful in trapping hot and cold break. However, they are much more bulky (up to four times the space required for pellets, a real issue when storage is limited) and can suffer more degradation while being stored over time until the next hop harvest. Whole hops are the traditional form and it is believed that they provide the best aroma contributions. The lupulin glands are generally intact, and this supports this belief. Pellets are more likely to be fresh than whole hops, but heat is applied in their manufacturing and this causes the loss of some of the essential oils. However, pellets are much better protected against oxidation and other storage problems, and because the resins in the lupulin glands are more exposed by the process, it is believed that pellets provide better bittering potential. When dry hopping, whole hops float while the pellets tend to sink. This can be a utilization issue if the pellets get covered by trub in the fermenter. Plugs are an intermediate form sharing more similarity with whole hops, but having better storability - both because of smaller space requirements and also better protection against oxidation. Plugs are only produced in England, so there is a smaller number of varieties available and the process may be discontinued in the future. Also American hop varieties need to be shipped to England and then back to the US before we can use them. Thus freshness can be an issue. In general, the industry handles hops much better now than in the past. Both in the cold storage used by the hop brokers and also the better handling, packaging (especially the use of oxygen barrier bags), and cold storage by the retailers. Each form has its proponents and critics. The choice is really personal, depending very much on your own equipment and brewing processes.
Now that we understand a bit more about hop varieties and forms, the components that contribute to bitterness and flavor, and the methods for using hops; let's take a look at how we determine hop usage levels, or just how bitter is that beer? Hop utilization used to be expressed in pounds per barrel, in recent years we have developed the concept of a bittering unit. A common method is now used world wide (there used to be different measurements used in the US and Europe). This common system is called the International Bittering Unit, or IBU (sometimes shortened to BU, or bittering unit). The main difference here is that the old way measured the amount of hops used in making beer, the new method measures (or approximates) how much bitterness actually makes its' way into the finished beer. There are also older systems (AAU and HBU) that are still used by some. Actually, the AAU (Alpha Acid Unit) and HBU (Homebrew Bittering Unit) are essentially the same measurement system.
The higher the IBU number, the more bitter the beer. IBUs can range from as little as 3 in a style like Berliner Weisse to over 100 in some barleywines, not to mention highly hopped IPA's such as Alpha King (which some say is over 200 IBUs). Keep in mind that formulas and even instruments like the spectrophotometer provide only a approximation of what hops provide in beer. The best and most discerning instrument is your tongue and pallet when it comes to determining both bitterness and the more subtle nuances of hop flavor.
We must also consider hop utilization. Unfortunately for us, losses occur in many places in the system. Much of the alpha acid put into the wort is only potential. There are many factors that affect our hop utilization percentage. Among these are the amount of hops used, their form (whole, pellet, plug, use of hop bag) and age, the boil itself (conditions, temperature, time, whole or partial boil, batch size), wort gravity and pH, not to mention fermentation issues like yeast growth & flocculation, blow-off, loss to trub, etc. It is generally considered that hop utilization will be in the range of 20-30%.
Any formula to calculate hop utilization must take into account all of these factors (and more). This can get extremely complicated and I won't discuss it here. Suffice it to say that the most commonly used formulas were developed by Jackie Raeger and then later modified by Mark Garetz. If you want more info, a good place to check would be Chapter 8 of the Garetz book, Using Hops. Many spreadsheets are available online to do these calculations for you, or you could use one of the excellent brewing programs like Jeff Donovan's ProMash.
Let me conclude by saying that your attitude towards hops is a personal one formed by taste, style preferences, and brewing philosophy. Many brewers, as they gain more control of the process, begin to experiment with pushing the envelope, seeing just how hoppy they can make their beer. For some this is a passing phase, giving way to an interest in a more balanced approach. For others, the true hopheads, this only leads to a search for that Holy Grail, the Hoppiest of Beers. If you don't know yet where on the spectrum you fall, try answering this question. When you consider balance, do you first think of enough hops to balance the malt sweetness; or do you think is there enough malt to support the hoppiness?
I'd like to suggest that if you have any questions concerning hops, don't take them to either Dr. Bob (need I say more?) or to Sue. While Dr. Bob insists that he's never found a beer that's hoppy enough; Sue maintains that she doesn't like hoppy beers, much preferring malty styles like the Scottish Ales. But then the beer she's most likely to order at Market St Pub on a Saturday night is Flying Dog's Doggie Style Pale Ale. Not exactly a malty beer, eh? She's also come to really appreciate Wayne's Barleywine, obviously a confused woman.
In closing, I want to remind you of our Hogtown Brewers' motto; "Since 1985, more hops than our lawyers advise." And for extra credit for the BJCP study group, answer the following question - Is Mark a Hophead, and why?