Part I: From Farm to Market to Brewery, Hops Lead a Fascinating, Delicate Life
Originially Published By Don Put (Brewing Techniques, Volume 4, Number 2)
As an ingredient that plays such a major role in the taste and character of your beer, hops deserve a close look, smell, and taste.
Ever since the first hops were added to beer, they have been a lively ingredient of considerable interest to brewers. When the first hopped beer, known as “hopping beer,” was introduced in England many hundreds of years ago, it met with considerable opposition. The use of hops was even banned on several occasions. But once the hop took hold in brewing practice, its impact was so great that it even changed the name of the finished product. Traditionally, an unhopped fermented malt beverage was referred to as an ale; once hops were added, the drink became beer. Today, this distinction has been lost, and the term ale has more to do with the fermentation characteristics of yeast than the addition of hops. Nevertheless, the importance of hops remains.
A basic understanding of the role that hops play in the brewing process is essential for any brewer wishing to progress quickly along the path toward brewing excellence. The topic can easily fill a book (and has, in fact [1,2]). For our purposes, this installment of Home Brewery Basics begins a two-part series on the fundamentals of hops and their application in the brewing process. This first installment provides an overview and background of hops and hop products. The next issue will cover the specific details of their use in the brewhouse and equipment considerations.
Botanical Background
The hop plant is native to North America, Asia, and Europe. Hop cultivation and breeding spread from the region that is now Belgium and the Netherlands to England and, finally, to the colonies in America. The exact date of the introduction of hops into brewing is open to debate, but we can presume it was standard practice by the time of the Reinheitsgebot, the Bavarian Beer Purity Law of 1516. This law mandated that beer be made only from water, malt, and hops (yeast was, of course, unknown at the time).
Breeding: Many of the varieties now used for brewing were selectively bred from “wild” ancestors to increase the characteristics that make them desirable in beer. Hop breeding programs today concentrate on producing high-quality hops that are easier to cultivate (higher disease resistance and greater yield) and that possess a higher bittering potential along with the correct level of essential oils and attributes that allow stable storage.
The hop plant that brewers use, Humulus lupulus, belongs to the same plant family as Cannabis, which we know of as marijuana. The hop plant, however, lacks its relative’s psychoactive resins. (Stories persist about marijuana cultivators’ attempts to make an “unbustable” hybrid through grafting the stems of hops to the base of marijuana plants, but any such effort is doomed to failure because the illicit chemicals are produced in marijuana’s leaves and flowers, not in the stem or roots.) Hops have traditionally been thought to induce sleep; herb teas and even hop pillows are sold to people with sleeping trouble. Of greatest interest to us, however, is that brewers figured out early on that highly hopped beers didn’t spoil as quickly as their unhopped or lightly hopped counterparts. So hops became a welcome addition to beer not only because of their bittering, flavoring, and aroma qualities, but also because of their preservative qualities.
Plant structure: The hop plant consists of a rhizome, the underground stem from which the roots develop, an above-ground vine (or bine), and hop cones, or flowers. During the growing season, a hop vine can grow up to 1 ft a day, potentially reaching a height of 25 ft or more. When it comes time to harvest the cones, the plant is cut back to ground level, leaving the rhizome to lie dormant until the next growing season. Once harvested, the cones are immediately dried and then packaged.
When it comes to brewing qualities, the hop cone is where the action is. Within the cones are lupulin glands that contain resins and essential oils. The female plant bears cones that contain thousands of these all-important glands. Because a fertilized female hop plant will turn its energies from resin-making to seed-making, male hop plants are unwelcome in all circles. Most hop cultivation regions have very serious eradication programs to rid their area of pollen that might drift in from errant males growing wild along stream banks. Hop breeders very carefully pollinate selected plants in highly controlled laboratory-type environments and then remove selected females for production farming.
Resins and Essential Oils
Of the two types of resins — hard and soft — that make up approximately 15% of the hop plant’s composition, the soft resins contain the chemical component that imparts the bittering qualities for which hops are known and valued. This component of soft resins is called alpha-acid. The alpha-acid itself is bitter, but it becomes even more bitter when isomerized in the boil to iso-alpha-acid. The amount of alpha-acid present in a particular variety and harvest year is given as a percentage on a hop analysis sheet; it should be clearly marked on the packaging of any hop variety that you purchase.
It is important to keep one caveat in mind: Alpha-acid analyses can be used only as a rough guide, because they give only a representative percentage for the hops you are buying and can’t possibly account for deterioration once the hops have been packaged, stored, and transported. In spite of this, it doesn’t hurt to have some good reference numbers from which to work.
Resins: Depending on variety, the amount of alpha-acid present can range from 2% to 15%. The lower part of the range usually represents the noble hops (those descended from the Central European, land race varieties such as Hallertauer Mittelfrüh, Hersbruker, Tettnanger, Spalter, and Saazer [3]).
The other two constituents of the soft resins, beta-acids and uncharacterized soft resins, play a far less defined role in beer production. Some of the bittering products that result from the oxidation of beta-acids during storage compensate a little for the loss of the alpha-acid’s bittering potential over the same period of time. Nevertheless, it is preferable to use fresh hops, because they deliver a “cleaner” bitterness than those associated with oxidation by-products.
Essential oils: Essential oils make up about 0.5–3% of the hop cone’s composition. The hop presence and aroma in finished beer is directly related to essential oils. The two main constituents of essential oils, humulene and myrcene, are volatile hydrocarbons that evaporate quickly once the hops are added to the boiling wort. Although humulene and myrcene — and the by-products that result from the oxidation and boil reactions of these two oils — make up a major part of a beer’s hop signature, it is more likely that a synergistic action of many components makes up a hop variety’s characteristic aroma. Essential oils contain many components, and their contributions to the finished beer remain, for the most part, a mystery.
Hops’ Many Forms in the Marketplace
Hops are commonly available to home brewers in whole (“loose”), plug, or pellet forms. The decision about which form to use depends on your preference, based on both a subjective evaluation of the hop’s characteristics and the demands of the brewing equipment being used. Each form has its good and bad points.
Whole Hops: The most unprocessed hop form is, of course, the whole hop cone. Ideally, the cones appear to be in a just-picked state; in reality, though, a lot of the cones are not completely intact after handling.
In my brewing setup, I like the way whole hops filter out the trub once I’ve finished boiling and chilling the wort. I use stainless steel “Chore boys” (scrubbing pads) — the large ones available from restaurant suppliers — as filter media because whole hop cones are too large to pass through the small openings in the coils of stainless steel. The whole hops coat the stainless steel loops and form a kind of secondary filter. Whole hops also look pretty good churning around in the boiling wort. When they are fresh, they provide the most unspoiled form of essential aromatic hop oils.
The key word here is “fresh,” although freshness has become less of a problem with the advent of numerous high-quality hop suppliers for home brewers. The downside to whole hops is that, once the original package is opened, great care must be taken to prevent the staling effects of oxygen. Whole hops also take up considerable storage space.
Plugs: Plugs (also known as Type-100 pellets) are whole hops pressed into ½-oz disks about 1¼ in. in diameter and ¾ in. thick. They are usually sold in vacuum-sealed oxygen-barrier bags in 5-oz quantities. At first glance, plugs appear to be the ideal form of hops because they have most of the “fresh” characteristics of whole hops, are more protected from damaging oxygen, and take up less storage space. When tossed into boiling wort, plugs quickly expand and break apart into the whole cones from which they were made.
All of this sounds fantastic; however, a couple of drawbacks merit attention. First, a majority of the available hop varieties are not processed into plugs because they must be shipped to England for production (England currently has the only operational plug-making equipment). Second, difficulties arise when you try to break up the ½-oz plugs into small pieces (this is mainly inconvenient, not impossible).
Pellets: Pellets look just like rabbit food and are made by grinding the whole hops into powder and then pressing and extruding them through a die. The hop processors take care to avoid excessive heat during this process to prevent the destruction of the resins and essential oils. Hop pellets seemingly offer the best of all possible worlds and, as a result, are very popular in breweries of all brew lengths.
When the hop powder is forced through the extrusion die, a layer of resin hardens on the outside of the pellet, effectively preventing oxygen from passing into its interior, making for a small, tightly sealed package about 3/16–¼ in. in diameter and ⅜ in. long. The lupulin glands are also crushed during processing, so resins and essential oils are readily dispersed in the boiling wort once the pellets are added. The hop charge can also be cut back by about 10%, because the pellets offer up their alpha-acids more readily than do other forms. Weighing out hop pellets is a snap, and they take up less than one-quarter of the space occupied by the original volume of whole hops.
Pellets have only a few processing disadvantages worth considering. Some people have argued that the processing negatively affects the essential aroma–contributing oils. In addition, processed hops are harder to keep out of the fermentor without whirlpooling (a process in which trub and hops collect on the bottom of the kettle in a small, centered mound, allowing the clear wort to be drawn off from the sides). Many brewers prefer using a kettle filter, which may make them lean toward a more easily filtered hop form. The topic of kettle filters falls into the minor-equipment-that’s-vital-to-the-brewer’s-mental-health category and could easily be the topic of an entire column. (Stay tuned, keep brewing, and look for this topic to come up again in the future.)
Other hop forms: The homebrew market also offers hop extracts, essences, and oils that provide a means of enhancing certain hop characteristics in finished beer. These products can be used to increase bitterness (iso-alpha-acid extracts), late hop presence or flavor (otherwise obtained by adding hops late in the boil), or hop aroma.
Current extraction processes involve the use of either solvents or carbon dioxide, though solvent-based methods are falling by the wayside in favor of the cleaner carbon dioxide method, which extracts compounds using high-pressure, relatively low-temperature, liquid carbon dioxide. I encourage you to seek out only those extracts made using this process. Lower temperatures are less destructive to delicate hop components, and the use of carbon dioxide ensures that no processing chemicals carry over into the finished product.
Isomerized hop extracts. If your goal is to add more bitterness to a batch of underbittered beer in a hurry, then iso-alpha-acid extracts are the product of choice. Added after fermentation — either in the bottling bucket or keg — they provide an effective and reliable means of correcting deficiencies; however, care must be taken to avoid overdoing it.
Some extracts are calibrated in international bitterness units (IBUs) per gallon and are easy to use because the quantities are already figured out for you. Although these extracts work great for “patching up” finished beer, don’t use them as the sole source of your beer’s bitterness because boiling the hops with the wort provides other benefits besides just adding bitterness.
Hop essences. Late hop essences contribute to the taste profile of the beer. The ones that I’ve seen add either floral or spicy notes along with an increased perception of mouthfeel. They can be used to correct for blandness — with an emphasis on the word “correct.” To my mind, the best way to remedy faults is to adjust aspects of the brewing process in subsequent batches, rather than to rely solely on extracts. It is nice to know, though, that products are available to help you salvage a marginal batch. As with iso-alpha-acid extracts, currently available products take most, if not all, of the guesswork out of using late hop essences.
Hop oils. Although hop oils have been around for quite a few years, only recently have they become readily available to home brewers in a user-friendly form. The essential aroma-producing oils are suspended in water to form an emulsion that is easily added to the finished beer. Once added, the effect is similar to dry hopping in that the hop aroma of the beer becomes greatly enhanced. As with iso-alpha-acid extracts, the calibrated oil extracts on the market make measuring easy.
The only downside to the oils results from the slim selection of hop varieties represented. Oils are available in single-variety (East Kent Goldings, Cascade, Fuggle Northdown, and Challenger) or blended forms. As you can see, the selection of single varieties is small but will, no doubt, increase with demand. Judiciously used, hop oils can enhance the presentation of your hand-crafted beer.
Hopped malt extracts. This topic may seem a bit out of place in a discussion about hops, but many beginning extract brewers rely on hopped malt extracts to form the base of their brews. Although there has been a great deal of rumbling and a few articles on the fermentable makeup of malt extracts, relatively little information has been available on the “hoppiness” of hopped malt extracts. The most thorough treatment of this subject was six years ago (4), and I’m sure that an up-to-date reassessment would be welcomed by the home brewing community, if for no other reason than to correct for any formulation changes with regard to IBU levels that have taken place since. Those of you who use hopped malt extracts and would like to know the basic IBU level so that you can tweak it a bit should contact the manufacturer and request the information. Unlike the issue of fermentable makeup, the bitterness level of hopped malt extracts is noncontroversial and the information should be readily available.
One thing to keep in mind when using hopped malt extract is that the hops will contribute only to the bitterness of the final beer; they do nothing for the hop presence or aroma. If you currently use hopped malt extract, you may wish to start adding fresh hops later in the boil to add to the hop profile of your favorite recipe. Once you have started experimenting in this manner, you can switch to unhopped malt extract and add all the hops yourself, giving you ultimate control over one of the most important ingredients in your homebrewed beer.
Evaluating and Purchasing Hops
Alpha-acids are unstable and deteriorate rapidly when exposed to oxygen, light, and high temperatures, so it is imperative that you buy your hops from a homebrew supply store or hop merchant who stores (and labels) the hops properly. Freshness is by far the most important criterion when shopping for hops. Choosing high-quality hops involves the use of your senses. If you pay attention to what you see and smell, choosing high-quality hops will become second nature.
Smell: First off, try to smell the hops through the packaging. If you get a big whiff of hops — or any whiff for that matter — find another supplier, because these bags are not of the oxygen barrier type and the hops have been exposed to air. In whatever form, fresh hops should smell strong and clean, but you should be able to smell them only after opening the package. Stale hops acquire an easily identifiable “cheesy” smell; they can also smell a bit “skunky” if they’ve been exposed to heavy doses of light. Avoid any hops that exude these olfactory sensations.
Color: Different hop varieties are different shades of green, but they should be green. The drying process can slightly shift a hop’s hue within the green spectrum (toward yellow). These variances, and an occasional brown cone in a bag of whole hops, are of little concern. Steer clear from a bag full of brown cones or pellets and run — don’t walk — to another supplier.
Shape/structure: As far as the physical shape of the hops, just make sure that you don’t have to search for an intact cone in a bag full of whole hops. Most bags of whole hops that I’ve purchased from reputable suppliers have contained a large percentage of intact cones. Some destruction of cones during handling is inevitable. The same holds true for pellets. Some hop “dust” is normal at the bottom of the bag, but be wary of a bag with more than a trace amount, because pellet dust degrades faster than any other hop form. When broken, pellets should “snap” apart and you should have two intact halves in your fingers. Any pellets that crumble into powder under the slightest pressure are old and are best used for composting.
With all of the education in the home brewing community over the past decade, the hop market has improved greatly for home brewers. The chances of finding an ill-informed or ill-equipped supplier has dramatically decreased, but it never hurts to be an informed and prudent buyer.
Packaging and Storage
With freshness the key to proper packaging, the ideal storage method involves using oxygen-barrier bags or, once at home, Mason jars, together with either vacuum-sealing (for bags) or an inert-gas atmosphere (for bags or jars). The usual gasses are carbon dioxide, which is inexpensive and readily available to keggers, and nitrogen, which is a little more expensive but can sometimes be found among brewers who seek the perfectly poured pint of Guinness. Once opened, repackage and carefully store the leftover hops, making sure they are not exposed to light.
The idea behind both of these storage practices is to prevent damaging oxidation reactions. The best place to store hops, whether in their original packages or not, is in the freezer. I use the Masonjar-and-carbon-dioxide-style of repackaging and have stored hops for more than a year without noticeable degradation. If you don’t have access to a vacuum food sealer or to protective gasses, just force as much air as you can out of the package, seal tightly, and store in the freezer. Ideally, though, you’d want to use up the hops as soon as possible to guarantee maximum freshness.
At minimum, the label should indicate the alpha-acid content of the hops. I recently received a bag of Hallertauer Mittelfrüh hop pellets from the Boston Beer Co. It has the most complete label that I’ve ever seen. There is no reason why all suppliers can’t make this information available to home brewers (Boston Brewing Company isn’t even a hop supplier, but periodically offers imported German hops to home brewers).
Personal Experimentation is the Key
As you can see, the hop flower holds many secrets in its role as a central player in the makeup of our beer. As with any brewing process, piece of equipment, or ingredient, a good general understanding is a necessity before jumping into specifics. The present article covers only half of the story — the nature of the hop, its various forms in the marketplace, and its care and handling. The next installment of Home Brewery Basics will cover the world of applications of hops in the brewhouse.
Until then, I encourage you to expand your experimentation with this critical ingredient of your fine, hand-crafted beer.
References
(1) R.A. Neve, Hops (Chapman & Hall, London, 1991).
(2) M. Garetz, Using Hops (HopTech, Danville, California, 1994).
(3) D. Van Valkenburg, “A Question of Pedigree — The Role of Geneology in Hop Substitutions,” BrewingTechniques 3 (5), pp. 54–59 (September/October 1995).
(4) “AHA Guide to Hop-Flavored Malt Extracts,” zymurgy 14 (4), (Special Issue 1990).
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