Article

Hop Creep Explained, Backsweetening, and Maximizing Malt Freshness

Q
Alright, can somebody please explain this hop creep phenomenon to me? I had a DIPA that I bottled, which ended up way over-carbonated. A friend mentioned it may be due to hop creep, but he didn’t know the specifics of it.

John Sullivan
Avon, Indiana

A
Hop creep is a term that has been recently popping up in commercial craft brewing circles to describe increased attenuation following dry-hopping. Reports in brewing literature indicate that a small handful of craft breweries may have been aware of this general phenomenon for the past few years, but most were not. The industry’s understanding of what was happening was changed in 2017 by research conducted at Allagash Brewing that followed their very first dry-hopped beer, Hoppy Table Beer, brewed in May of 2016. Allagash closely follows the progress of carbonation and attenuation in their quality-control (QC) lab because they bottle condition almost all of their beers. Because of their diligent practices, they were able to flag that something was amiss with their first foray into dry hopping.

What they observed were increases in carbonation and decreases in real extract that exceeded their experienced expectations. After 3 weeks, the carbonation level in bottles of Hoppy Table Beer were over 4.5 volumes, or more than 1.5 volumes greater than their 3.0 volume target. On the surface, this looks similar to beer that contains Brettanomyces, but that was not the case here.

The QC group at Allagash embarked on a series of experiments to determine the root cause of this phenomenon and ended up using dry-hopped Coors Banquet beer as a model system. Their model system behaved like their Hoppy Table Beer when yeast was present and became dryer and more carbonated after being dry hopped; samples without yeast did not demonstrate the same behavior. Allagash collaborated with Dr. Tom Shellhammer’s research group at Oregon State University (OSU) to further the investigation. Shellhammer’s team began by repeating the trial using dry hopped Coors and were able to repeat Allagash’s experiment.

After digging deeper into the potential causes of the phenomenon, the OSU team found the smoking gun; hops contain several amylolytic enzymes, including amyloglucosidase (AMG). When AMG is added to wort or beer, limit dextrins (those carbohydrates left behind after alpha and beta amylases hydrolyze amylopectin) are broken down into the fermentable sugar glucose. What Allagash and OSU observed in the model system with Coors Banquet, hops, and yeast was glucose production and subsequent fermentation by yeast as a direct result of AMG degrading limit dextrins in the beer. This is what brewers call hop creep, a phenomenon last reported in the brewing literature by Janicki and others in 1941 and, nearly 50 years earlier in 1893, by Brown and Morris.

The odd thing about this topic is that dry hopping bottle-conditioned beers is not a new thing for craft brewers, and reports of hop diastases are certainly not new. But over-carbonation in dry-hopped, bottle-conditioned beers does seem new. Take Sierra Nevada as an example; their Bigfoot Barleywine and Celebration Ale are both generously dry-hopped, contain plenty of chewy dextrins, are bottle-conditioned, and neither are known for their extreme levels of carbonation after cellaring (contrast this to Orval that is bottle-conditioned with Brettanomyces). Hop creep has turned into a very hot hop topic and it will be interesting to learn more about this as brewing scientists uncover more findings. Practical brewers anecdotally know that this phenomenon is not associated with all hops, and there does not seem to be any obvious association with specific varieties or hop growing regions. In other words there is still a lot of mystery in this occurrence.

What makes hop creep a very big deal is its potential to cause package explosions at home or in the market. It’s bad enough for commercial brewers that hop creep results in over-carbonated beer and increases a beer’s ABV beyond what the label states, but the liability concerns surrounding package failures is huge. Homebrewers definitely need to be mindful of hop creep by paying attention to changes in carbonation levels in bottle-conditioned beers and staying abreast of this topic as research continues peeling back the layers of this interesting topic.

Q
I recently had an excellent draft honey wheat at Whole Foods. As I enjoyed the brew I realized there was a nice honey aroma and flavor, but none of the additional alcohol caused by the honey. In the past when I’ve added any additional sugars (honey, fruit, etc.) in the secondary it caused additional fermentation and additional alcohol.

I know I can add preservatives to the secondary to stop or at least limit the yeast, but if I do add these how will I then be able to bottle carbonate the brew? Won’t the yeast be prevented from processing the priming sugar and therefore prevent carbonation?

Joe
Mars, Pennsylvania

A
Joe, thanks for the good two-part question about using brewing sugars like honey for special flavors and the question about how to bottle condition beers that may contain fermentable sugars. These are two independent brewing questions and are best addressed as such.

When adding fermentable brewing sugars to a batch, it is important to consider how these sugars will be expressed in your beer. I like formulating beers from the ground up, and factor in all ingredients when developing a recipe. This means that if the plan is to develop a brew with 5.5% ABV, for example, that everything added to the beer will be considered; a bit different than simply adding honey to a recipe that is designed to produce 5.5% ABV beer without any honey. The description of your tasting experience describes a beer that was designed with honey from the ground up with the honey an integral part of the beer’s balanced flavor profile.

Using brewing sugars does take a bit of mental calibration however, because when most of these sugars are added to wort they are fermented along with the malt sugars (lactose being the one exception to this rule). This means that what we perceive as honey flavor, for example, expresses differently in the finished beer. The first word that comes to mind for most folks when pondering honey is sweet, but adding honey to wort does not necessarily make for a sweet beer. What honey does add to beer are honey aromas, and those aromas can cue the perception of honey in beer, especially when the beer may have a sweet finish that mirrors our natural perception of honey. This is one reason why a malty brown ale works well with honey.

Brewing with brewing sugars is not always about trying to preserve sweetness

Brewing with brewing sugars is not always about trying to preserve sweetness. The herbal and floral notes of honey marry well with the nose of a saison, and the simple sugars in honey ferment to dryness and can be used to produce a dryer finished beer if that is desired. Some brewing sugars, like Belgian candi sugars, may contribute color and special flavors. Table sugar can be used to boost alcohol and dry out a beer with little else. Fruit sugars usually bring acid, color, and aroma to the party. And lactose can be used to boost final gravity, add body, and serve as a canvas to layer decadent flavors onto an otherwise typical beer. The point is that most brewing sugars are used to contribute fermentables to wort and some sort of special component that malts are unable to achieve.

A key thing to keep in mind when adding sugars to wort is that they dilute yeast nutrients. As long as they contribute less than about 25% of the total extract, the nutrient dilution is not an issue. But sugars can dilute wort nutrients when used in excess and lead to solvent-like and “hot” flavors. Keeping the yeast basics in mind is always important, especially when pushing sugar additions; always use fresh, healthy yeast cells, pitch appropriately, consider adding zinc and/or nitrogen and phosphorous in the form of yeast nutrients, and aerate your wort. Rome was not built in a day, and using brewing sugars may require practice before yielding really great beers. Paying attention to off-flavors related to fermentation and adjusting your practices as needed is one tip that can really take these brews to a higher level.

Your second question is not so easy. Preserving residual sugars in a style like honey wheat, presents a real dilemma. One way to accomplish this goal is to use a preservative, such as sodium metabisulfite or potassium sorbate, to prevent re-fermentation. But as you point out, these preservatives will also prevent bottle conditioning. This is just one of those cases where a sacrifice has to be made, and the easiest thing to do is to force carbonate these types of beers and do something that prevents re-fermentation.

Current popular styles where in-package fermentables are desirable include fruit beers, pastry stouts, and milkshake IPAs. Not all brewers are keen on using preservatives and there are two other approaches that can be used. The best method is to pasteurize these beers in the package, but most breweries who are brewing these styles do not have tunnel pasteurizers, and pasteurizing at home is not a realistic option unless you simply want to conduct a science project. The other method many brewers are turning to is simply packaging beers with fermentables and storing cold. There are four words that succinctly describe this last method; it is no guarantee! Contrary to popular belief, ale and lager strains can continue fermenting at much lower temperatures than those used for rapid fermentation given the proper conditions.

This is where homebrewers really have a leg up on commercial brewers. What is the purpose of brewing beer at home? Is it to create a product that mirrors commercially available beers, or is it to brew something that you can enjoy at home? Dumb question, for sure, since the obvious answer is that homebrewers brew beer for friends and family. This means that you can give instructions to your consumers that probably would fail for a commercial brewer. Consider these styles as beers that require some user participation.

Imagine you want to brew a dry, tart, and slightly salty Gose, plus a little sweetness for balance. There are some clever things that could be done here, but the most solid options are in-package pasteurization or force carbonate plus preservatives. Or you could simply add a shot of sugar to the beer before drinking! Seriously, take a page out of the Berliner weisse playbook and add that shot of waldmeister syrup, herbed honey shrub, or flamed sugar and Bourbon when the beer is poured. Where does it say that all of the flavors in a glass of beer have to be in the bottle, can, or keg prior to imbibing, and where is written that Berliner weisse is the only style where finishing at the time of consumption is allowed? I hope this simple approach is not a disappointing answer to a challenging question. The one downside is that this won’t work well if you plan to enter a competition!

Q
There is a specific flavor and aroma that I am trying to coax from my beer. The best way I can describe it is truly fresh malt flavor and aroma, not malt sweetness, that makes it into the finished beer. I was sitting at Founder’s a while back and ordered a PC Pils, this beer had the flavor and aroma of fresh baked bread and boiling wort. It melded perfectly with the fresh American hops. I have been chasing this dragon for quite some time. I have tried different malts (Munich, Vienna, Aromatic, Melanoidin, etc.), different maltsters, single infusion mashes, decoction mashes, even different boil times and intensities. Looking for other variables to explore; maybe mash pH? I rarely, if ever, stray from 5.3.

Brad Lawrence
via Email

A
I have been on this same journey before and it can be a real challenge chasing elusive flavors that sometimes seem impossible to capture, and perfect malt flavor is one such genie. It’s hard to play this game without starting with malt: They may be lacking in the flavor you are chasing. Although you state in your question that you have tried different malts, don’t walk away from that exploration. Malt flavor is influenced by where barley varieties are grown, the variety itself, and how the barley is malted. Try to uncover more about the malts used in the beers you really like; there may be some commonalities. For the sake of this question I am going to assume that you are seeking maltiness in styles like Pilsner and helles lagers, and pale, and lightly hopped, ales.

When I troubleshoot brewing problems, I roll through the brewing process in my head to think about places to focus attention. Water, malt, yeast, and hops. Milling, mashing, boiling, cooling, aeration, fermentation, racking, and packaging. I am going to venture out on a limb with this one and suggest that you focus on water, mashing, and oxygen pick-up in your process following wort production. The flavors you seek are delicate, and nuances do have a significant influence on things when you start to strip layers of complexity back to focus on the subtle.

Water represents ~90% of most beers and you need to check that box when embarking on this journey. Very pale beers, especially those with superb balance and cleanness of flavor, greatly benefit from water that has very little in it other than 50-100 ppm calcium and the requisite balance of calcium and chloride. Readers of my column know that I am a fan of reverse osmosis (RO) water because it is easy to adjust, and free of components that may not show up on the brewing radar until a problem pops up with flavor. Consider using RO water adjusted with an equal blend of calcium sulfate and calcium chloride (10 L/2.6 gallons of RO water with 1.7 g calcium chloride and 1.7 g calcium sulfate gives 100 ppm calcium, 96 ppm sulfate, and 107 ppm chloride).

When contemplating malt flavors, it is tempting to take a deep dive into thoughts about how decoction mashing just makes all traditional lager styles better. The problem with this sort of thinking is that traditional wort production methods were developed in conjunction with malt types that are all-but-extinct from the world of brewing. Most commercial breweries these days use relatively short and simple mashing methods when possible because modern malts are generally well-modified and highly enzymatic, and simply do not require long, complex mash methods. Plus, breweries with newer brewhouses are focused on minimizing energy consumption during wort boiling, reducing thermal stress caused by excessive wort boiling, and using engineering solutions to reduce wort dimethyl sulfide (DMS) that also reduces energy use. This means color and flavor development during wort boiling is something not seen much in many commercially-brewed craft beers. You reference Founder’s Brewing in your question; Founder’s is well-known for their use of infusion mashing. Their largest brewhouse in Grand Rapids, Michigan features a 300-BBL system where they mash directly into the lauter tun using two, very large, grist hydrators, and a kettle designed to minimize thermal stress while maximizing DMS removal.

How does mashing and boiling relate to preserving these delicate malt flavors? Depending on a variety of factors, such as lipoxygenase activity in very pale malts, degree of malt modification, and complexity of mash; wort composition and wort flavor can be skewed in a direction that often ends in aged-beer flavors. May I suggest for your winter reading, which may further your understanding of these general concepts including the relationship between malt lipoxygenase activity and staling flavors in beer, wort FAN and its influence on beer flavor, and how thermal stress during wort boiling influences the thiobarbituric acid index (TBI).

The last topic that I really believe relates to your quest is oxygen pick-up in the downstream processes following wort production. Chasing oxygen pick-up is all about the details, and examples include removing air from empty hoses used in racking, completely purging carboys and kegs of air before filling with fermenting or finished beer, evacuating air from bottles during filling, capping on foam, making sure that fittings and couplers do not have leaks that can suck air into the system during use via the Venturi Effect (especially real when pumps are used), and using deaerated water whenever adding water to fermenting or finished beer. This pursuit can be taken to the next level by pursuing low dissolved-oxygen procedures in the brewhouse, but I don’t think those methods are required to sate your thirst for beautiful malt notes.

There is no single approach to chasing this dragon, but if I were to design a plan it would begin simply. Excellent base malt, very limited use of specialty malts, simple water, mash method aligned with malt, minimal thermal stress in wort boiling, clean fermentation, and obsessive attention to oxygen pick-up. Additional complexity only added as needed. Good luck in your pursuit of the elusive!

Issue: January-February 2019