I have a random assortment of leftover hops in the back of my freezer that is about a year old. I always freeze the unused portions right away so they don’t have a lot of room temperature time. I’d like to use them up and I am wondering if I should use them strictly for bittering hops and calculate the AAU they would contribute to the recipe, and if there would be any adverse effects. Also, should I be accounting for any hop storage factor when calculating AAU?
Poughkeepsie, New York
As long as you used some sort of method to properly prepare your leftover hops for storage in your freezer, you can use these hops for either bittering or aroma. Hops have a good storage life when stored cold and in the absence of oxygen, and it is the norm for brewers all over the world to store hops for well over a year. After all, hops are harvested annually and the bulk of the hops harvested globally are products of the northern hemisphere. This means that if brewers really wanted to limit hop storage to six months that the global supply would not permit this practice.
So how is oxygen minimized from hops during storage? Hop growers literally smash the air from hops after the hops are kilned. The traditional method is to tightly pack whole cones into bales. In the industry, these hops are referred to as whole, compressed hops. Although a better preparation than a loose pile of dried cones, whole, compressed hops do contain some air. When pellet hops are made, whole, compressed hops are milled and further compressed into pellets. This whole process usually occurs under the cover of nitrogen, and the pelletizing process results in individual packets of tightly compressed hop powder that contain less oxygen than whole, compressed cones. Pellet hops are then typically packaged in vacuum-packed, foil, or Mylar pouches that have oxygen barrier properties. Hop processors and hop brokers do indeed store pellet hops in freezers, even though the hops are dry, to drastically slow oxidation reactions. This is very different from how hops were processed and stored when many of the famous brewing textbooks still referenced by many brewers were written.
There are probably a few readers who are thinking “why bother baling hops if the pellet process begins by unpacking the bales in preparation for milling?” The reason this seemingly unnecessary step is performed is for speed. The key to hop harvesting is to get the hops out of the field at the right time, kiln the harvest and quickly pack into bales. After the rush of harvest is complete and the crop put up in bales, hop processors can then start the relatively slow process of making hop pellets.
The key to saving leftover hops is proper storage. Since home freezers often concentrate sulfur aromas from food stored in the refrigerator, frozen foods can pick up aromas over time if stored in containers that permit gas transfer. Think plastic storage bag. A better container is a glass jar, but glass jars are hard to squeeze if you want to remove air! Fortunately, you can buy an adapter that allows a vacuum sealer to suck the air from a canning jar. While this rig may seem pretty extreme, it allows for leftover hops to be placed in a safe storage container for prolonged storage. And if you want to store different varieties in the same jar you can use sandwich bags to separate different varieties. You can also use zipper bags, squeeze the air out and put the zipper bag in a jar; many ways to tackle this problem. Just remember to do something to remove air and consider that your freezer may have some sulfur aromas wafting in from the refrigerator.
Now for some practical thoughts about using older hops that have been properly stored in a freezer. The hop storage index (HSI) is something that was developed to help describe and measure alpha acid degradation over time. I’ll try avoiding the ditch here with useless techie details … the HSI is a ratio of UV light absorbance at two wavelengths, where a larger value is indicative of oxidation of alpha and beta acids. Since a UV spectrophotometer is needed to determine the HSI, homebrewers are not going to be changing their recipes based on this value!
There are a few interesting things about hop storage. One is that certain varieties have better storage properties than others, making the HSI somewhat varietal dependent. Another interesting thing is that oxidized hops with a higher HSI value than fresh hops retain much of their sensory bitterness, and alpha acid oxidation during storage
does not translate to a proportional loss in bitterness. This is because the oxidation products are also bitterness. And the last little note about oxidation is that properly stored hops lose a very small amount of alpha in a year of cold storage.
The take home message is that storing hops in a freezer is a great thing to do with leftover hops. When properly handled, you can easily store hops for well over a year without significant loss of the brewing value of the hops. Since homebrewers and most small commercial brewers do not have labs equipped with the sorts of tools to chemically analyze hops, the best thing to do is smell stored hops (hop teas help with this evaluation) before use, and if you have hops that seem OK but not great, consider blending these hops with fresh hops and using them only for bittering additions.
I know that egg whites are used in clearing wine, but I’ve never used it for aiding in clearing beers. I was wondering if Mr. Wizard has any comments and advice on the use of egg whites in clearing beers. Waiting for the intakes of breath and cries of “No you heathen!”
No cries of heathen coming from me! This is a good question about a fairly common method used by winemakers. And the question that comes to my mind is why are egg whites used by winemakers?
The answer is that the albumen proteins found in egg whites bind with tannins. Young wines, especially red wines, have a palate-drying characteristic from grape tannins and egg white fining is a method used to round out a young, rough wine. Egg white fining is not primarily used to clarify cloudy wines, although removal of tannins does indeed reduce haze. Like all process aids, usage rate varies, but a common rule of thumb used by home winemakers is one egg white per 5–6 gallon (19–23 L) carboy.
So let’s discuss beer clarity and tannins in beer for a moment. Beer is cloudy during and after fermentation. The primary cause of turbidity at this stage of things is due to yeast suspended in solution. After fermentation is complete, yeast begins to settle and the beer starts to clear. This process is greatly improved by chilling beer because yeast flocculation is influenced by temperature. When unfiltered beer is chilled, other types of haze form. Temporary haze, commonly known as chill haze, forms when tannins associate with polypeptides (protein fragments). However, as the beer is warmed, the chill haze clears, hence the term “temporary haze.”
When beer is cycled from cold to warm and back to cold, temporary hazes begin to become permanent. This is why some consumers believe it is bad to buy cold beer if the beer is anticipated to become warm before eventually being cooled down again. I don’t prescribe to that line of reasoning since refrigeration slows oxidation and the transition from temporary to permanent haze takes several cycles.
Permanent haze also forms when beer is held cold for a prolonged time period. Both temporary and permanent hazes settle during beer aging and both types of haze can be removed by filtration. Temporary hazes explain why cold filtration is so important; if beer with a temporary haze, or the components of a temporary haze, is filtered warm enough to prevent the formation of the temporary haze, the haze will appear when the filtered beer is chilled.
Some beer finings are used to clear beer in lieu of filtration, and other finings are used to combat haze formation in filtered beer. Isinglass is the traditional beer fining used to settle yeast from cloudy beer. Silica gels are used to remove certain haze causing proteins and PVPP (short for polyvinylpolypyrolidone) is used to remove haze-forming tannins. There are of course other finings, but these are the primary types.
So how do egg whites relate to this? Well, the albumen proteins found in egg whites have similar properties to the collagen proteins found in isinglass. Although egg whites are primarily used by winemakers to influence flavor, brewers can use egg whites as a substitute for isinglass. I have used isinglass finings in beer, but have not used egg whites. Sounds like something I need to try!
The method used by winemakers is to add the white of one egg to 100 mL of water along with a pinch of salt to help dissolve the albumens. The mixture is gently stirred, added to the wine, gently mixed by stirring or pumping and allowed to settle for 2–3 weeks. The reaction between the albumen and tannins occurs very rapidly, but the settling process takes longer, explaining the 2–3 week rest.
When isinglass is added to a cloudy beer the yeast flocculation size and density is greater than the albumen-tannin flocculation (haze flocculation). This means that beer that is primarily clouded with yeast will clear fairly quickly, usually in a couple of days, when using isinglass. I suspect that egg whites would behave similarly. And if you don’t mind chill haze in your beer or don’t chill your beer cold enough for chill haze to form, this method may be all that you really want and something that is worth trying.
The bottom line is that egg whites may very well have a very handy spot in your brewing toolbox!
Here’s my take on IBUs, and I’d like it if you would weigh in — feel free to criticize or agree! I believe IBUs are nonsense. The IBU is calculated by factoring alpha acids added to the wort and the time of boil. There is a maximum calculated IBU of 100, even though some beers can seemingly go over this. One big issue seems to be the fact that hops are bitter … if you taste them before boiling, hops are BITTER! Which means that even dry hopping should increase bitterness. To add to this there are cohumulone compounds that are documented as giving a harsher bitterness, and this is not calculated into IBUs. The final blow comes from hard vs. soft water. It is well known that hard water causes a more predominant bitterness so a hard water Pilsner with the same IBUs as a soft water Pilsner will have more bitterness! I rest my case; IBUs are nonsense and should only be a crude guide.
This is an interesting take on things! You did not ask me a question, so I will share with you my view on this topic. But before I begin I will relay part of a story . . . last year at the Master Brewers Association of the Americas Annual Conference in Chicago, Illinois, Dr. Tom Shellhammer from Oregon State University led a series of talks about the International Bitterness Unit. After listening to three talks over the course of 90 minutes I really wasn’t sure if I was more or less confused about the IBU. And when I asked a question about what the IBU meant to the speakers the response was a bit of head scratching. It was a pretty interesting moment, and one that certainly got me thinking.
The IBU was developed as a way of assessing bitterness in beer. A brief history goes something like this: Moltke and Meilgaard developed a quantitative spectrophotometric method to approximate beer bitterness in 1955. Rigby and Bethune also published a spectrophotometric method in 1955 to approximate iso-alpha acids in beer. The Moltke and Meilgaard method better correlated with perceived bitterness and European breweries soon began using an adaptation of the method. Meanwhile, US brewers were using the Rigby and Bethune method. Eventually these two research groups collaborated to unite their methods, and in 1968 the method that is now known as International Bitterness Unit was adopted by the brewing industry.
Like many analytical methods, the IBU method starts with an extraction step and a measurement step. Bittering compounds are extracted from acidified beer using isooctane in a special shaker device. This method actually gives different results from the same beer sample if the shaking step is varied … hmmm, that’s a bit disturbing. After the sample is carefully shaken for a prescribed time period a gel-like clot develops in the shaker tube. A portion of the liquid around the gel is removed, placed in a cuvette, the cuvette is placed in a UV spectrophotometer and the absorbance at 275 nm is measured. The IBU value is equal to the absorbance at 275 nm x 50. A pretty simple method.
So what does the IBU represent? According to most things written about the IBU, 1 IBU represents 1 mg of iso-alpha acids per liter of beer. And this is how the coefficient of 50 was determined. But do compounds other than iso-alpha acids also absorb light at 275 nm? The answer is a resounding “Yes!” This brings up another obvious question; are there compounds in beer other than iso-alpha acids that absorb light at 275 nm? The answer is another resounding “Yes!” And to make things even more interesting, some of these compounds are not even bitter.
By the way, hops are certainly bitter, and anyone who has ever chewed a hop pellet can attest to that fact. But alpha acids are not soluble in beer, so dry hopping does not increase beer bitterness. There are numerous studies that clearly document this.
Your first point is that IBUs are calculated. While this is true, they are also measured. So what’s the practical message here? To me, it is that many brewers use calculations to go about determining how much hops to add to produce a target bitterness, and the reality is that our prediction is usually off. That in itself does not mean that the IBU is nonsense, it just means that analytical methods should be used to verify our calculations.
Major Question #2; is there a limit to iso-alpha solubility in beer? Yes. Most sources cite about 100 mg/L as the limit. In practice this means that is pretty hard to over-hop a beer if your goal is somewhere in the 100 IBU range. Cool!
The other practical point to consider is the way in which our senses work. Some things that are different are perceived as the same because the level is beyond our threshold of differentiation. Bitterness is like this. Beyond about 80 mg iso-alpha/L, things don’t get much more bitter. The value may increase but the response is about the same. This gets another “hmmm” in my book.
Notice how I just shifted my units from IBU to mg/L. This was pretty sly, and was done to avoid a circular argument. Let’s assume we brewed some big hop monster of an IPA with a calculated bitterness level of 90 IBU and decide to check our handy work using the isooctane method. The analysis is performed and the results indicate that our beer actually has 130 IBU. Holy Cow Batman! I must immediately post this on Facebook and advertise the beer’s 130 IBU at the pub, because this is one bad brew!
I think this is when the nonsense really starts to get piled on. If the isooctane method is supposed to correlate to iso-alpha acid concentration, and the solubility limit is 100 mg/l, how can the measured IBUs in this beer be 130? It’s the other stuff in beer that influences the method. As it turns out, these other compounds come from hops added for aroma in the form of late hop additions to the kettle or whirlpool or dry hops added to the fermenter. And if you are adding gobs of hops late in the boil, after the boil before wort cooling and in the fermenter as dry hops, chances are that you are boosting the IBU value without adding much to the perceived bitterness of your beer. This is really the Achilles heel of the method.
You are spot on that different hop acids have different bittering qualities. You mention cohumulone, and this is the alpha acid that is associated with a harsh bittering quality (this is a topic of debate). Incidentally, all of the noble hop varieties are low cohumulone. And there is no question that water salts influence the perception of bitterness, and at times, as with magnesium, contribute bitterness.
The IBU is not the “one number” that tells the whole story about beer bitterness. And when the isooctane method is used the number itself may tell different stories depending on how the beer was hopped. Fortunately high performance liquid chromatography (HPLC) separation and subsequent detection is able to tell a more complete story about iso-alpha acid content and this method is becoming the norm among growing craft brewers (larger brewers have been using this method for the past 20-25 years). But even with this, perceived bitterness cannot currently be measured with physical/ chemical methods and sensory evaluation is a vital component to this whole discussion.
In conclusion, the IBU was a number developed as a quality control tool. Measure IBUs in the same beer brewed the same basic way day in and day out and variations in the IBU do indicate that something has changed. Comparing IBUs among different beers is not as useful. Using the IBU as a marketing tool . . . to each their own! Thanks for the provocative thinking, Matt.