Heady, Hazy observations
This post is somewhat of a follow up to a recent post titled What in the haze are you doing? In that post I talked a bit about some of the new techniques that we're employing at Hops and Grain to try and coax new and exciting characteristics from the hoppy beers that we produce. Things like fermentation dry-hopping have been of particular excite for me.
Today's post is going to focus on a few other areas of hoppy beer production that we've been trying to improve at the brewery. Namely, dissolved oxygen and protein-polyphenol bonding. First let's discussed dissolved oxygen. DO, as it's usually referred to, is for the most part always something to avoid. At the end of any brew we intentionally introduce oxygen into the wort before adding yeast and allowing fermentation to carry on. After that our intent through all of our cold side processes is to avoid the introduction of dissolved oxygen as it's no longer desired. Nay, at this point it is abhorred.
We've implemented many different techniques for reducing the pickup of DO during transfers, centrifuge runs and packaging. Some have been very successful and some we are continuing to refine to produce the best packaged beer possible. The best beer ever made can be completely ruined by the introduction of too much dissolved oxygen at packaging. You can do everything right all the way to brite tank but a leaky gasket or faulty packaging process can introduce this demon and forever ruin a beer. Once that stuff is in there you really cannot get it out.
DO is a problem with any beer style. Lighter lagers that don't have as much flavor to hide behind can be particularly susceptible. If you've ever had a beer that reminded you of wet paper or cardboard you've likely experienced a beer that was oxidized. If you've had a beer that tasted like buttered popcorn you've likely had a beer that was oxidized (or just rushed through fermentation). Oxygen, especially when introduced into light colored beer brings about a chemical reaction creating trans-2-nonenal. This is produced through an enzymatic or nonenzymatic oxidation of lipids and oxidized free fatty acids. These lipids can be introduced via malt as well as hops. Most of the research that I've been able to find only discusses the carryover of malt and hop lipids derived from the brewhouse. One major reason why it's important to separate trub from wort that is headed to the fermenter is avoiding this lipid carryover. The small amount of hot side derived lipids that do carry over are mostly reduced during fermentation leaving just a small amount in finished beer.
The area that I've had a hard time finding any research is that involving the introduction of hops after or during fermentation and the potential lipid contribution to finished beer. In my previous post I mentioned that we've been testing new dry-hopping processes where we introduce hops to a fermenter at the height of fermentation. There are many desirable characteristics brought about by this but on a few occasions we've noticed some detrimental effects. Namely, rapid staling and in one case even browning of the finished beer when incubated at around 100 degrees F. So this got me curious about the potential introduction of lipids during this fermentation dry-hopping that wouldn't be present in our standard dry-hopping process. One area that I could imagine is simply that hops contain lipids and adding them during or after fermentation is introducing more than you would otherwise have without dry-hopping. I'm also curious if the interaction of yeast and hops during fermentation could cause a bonding of the lipids to yeast and increased carryover. Most of the hops that are introduced to a tank during dry-hopping eventually make their way to the bottom of the tank and are removed after the desired aroma, flavor and texture are achieved. But with fermentation dry-hopping we've noticed that the hops are almost immediately distributed throughout the wort and create a permanent haze that continues after fermentation. This, to me, would indicate that something different is happening with this type of dry-hopping as opposed to dry-hopping after fermentation with much less yeast in suspension.
Or could it be the increased polyphenol content contributed by the hops? Does fermentation dry-hopping create a more permanent polyphenol protein bond that wouldn't occur after fermentation? It is known that there is a small reduction of protein content in wort during fermentation but does the introduction of large doses of hops during early fermentation interrupt this reduction process and carry over larger quantities of protein than would otherwise be present? And what about high protein grains like wheat and oats that make up a sizable portion of the grain bill for the hoppy beers that we produce? SO MANY QUESTIONS!!
We commissioned a centrifuge in the brewery a couple years ago. We encountered a few issues with the first batches of hoppy beer that we ran through the centrifuge. First off, centrifuges offer many advantages to a brewery. Most manufacturers will tell you that you can reduce tank turn times as well as increase yields per tank. For us the intent was definitely to try and increase yields but the idea of turning tanks over faster was more important with our hoppy beers. After dry-hopping and crashing a beer it is my opinion that you immediately begin the process of degradation. While I will agree that many of our beers hit their stride about 5 days after canning I still believe that the quicker you can get a hoppy beer out of the tank after dry-hopping and crashing, the better. So we set about to reduce our post dry-hopping and crashing times with the "fuge". Pre-fuge we would dry-hop, rest and then crash the tank down to 32 degrees F. We would generally wait anywhere from 5-7 days while the yeast and hops settled, all the while taking cell counts to determine when the beer was ready for packaging. When we installed the fuge we starting transferring these beers sometimes just 24 hours after crashing. What we realized though is that the bonding of polyphenols and proteins that was taking place during the 5-7 days that we traditionally waited in the fermenter was now happening in the can. The increase in clarity that we would observe during those days in the fermenter was not just yeast dropping out of solution. It was also the formation of a bond between polyphenols and proteins that would then become heavy enough to fall to the bottom of the tank. Instead, that bond and ultimate fall to the bottom was happening in the can and leaving what we affectionately referred to as "asteroids" in the glass. Unsightly as it was, the flavor was not impacted at all. If you'd like to dive deeper into this process I would check out this article.
This particular observation from the article was most interesting to me and explained a lot about what we were seeing with these beers. "Proteins and polyphenolic compounds can combine to form soluble complexes. These can grow to colloidal size, at which time they scatter light, and grow even larger, which can lead to sediment formation. The protein/polyphenol ratio has a strong influence on the amount of haze formed; the largest amount occurs when the numbers of polyphenol binding ends and protein binding sites are nearly equal."
Knowing the cause of this sediment in our beer now, we set out to determine how to prevent it.
Enter the next character in our discussion, colloidal stability! Here's a simple explanation. The stability of a colloidal system is defined by particles remaining suspended in solution at equilibrium. Stability is hindered by aggregation and sedimentation phenomena, which are driven by the colloid's tendency to reduce surface energy. Seriously though, here's a much more digestible explanation taken from the Brewers Journal. The colloidal stability of beer refers to its propensity to form the non-biological hazes due to interactions between beer components, principally polyphenols and proteins, leading to the formation of visible precipitates. Colloid formation in beer typically presents as gelatinous or “jelly like” masses.
So we understand now that the "jelly like" masses that we were seeing in some of our packaged beers was the result of proteins and polyphenols bonding to form a colloidal haze that then became unstable in the can and formed visible precipitates. That left me with 2 huge questions.
Question 1. How do we create a permanent colloidal haze that doesn't become unstable and precipitate out?
Well that's a much harder question to answer and one that I don't yet have a definitive. We have employed some really interesting techniques to create a permanent colloidal haze and early tests have shown this to be successful. But much more exploration lies ahead. And I'll be honest, that's my favorite part.
Question 2. Does colloidal stability, or the lack thereof, accelerate oxidation in packaged beer?
I'll be honest, the first question has been a little bit easier to explore. With the second question I have found some research exploring the topic but, again, the missing variable is research that addresses fermentation dry-hopping rather than traditional dry-hopping in the absence of active yeast. Unfortunately the research leaves out a few variables to reach a definitive answer. That said, we do employ a dissolved oxygen meter at the brewery and have been able to track DO levels throughout our process as well as in the can during storage. The remaining analysis to date has been via sensory through tasting, smelling and observing the beers for signs of oxidative damage. But much more research is needed to fully answer my questions.
Another great resource to check out if you're interested in this topic is a blog by Scott Janish. His research is incredibly thorough but also very digestible to read. Check it out HERE.
At the end of the day if we were only selling our hoppy beers out of our tasting room and knew that every customer who purchases one was going to be consuming it within a week or so I wouldn't be so worried. But we thoroughly enjoy distributing our beer around Austin and beyond and thus take great responsibility in providing shelf stable beer to our distributors and customers. While we do control the timeframes of consumption via our canned on and best by dates we still want to be able to send a beer off to market and know that it's not going to go stale in a week or two.
So stay tuned for more results as these trials continue. And in the meantime swing on by the Hops & Grain Tasting room and grab a pint, six pack or crowler fill to go of some of our hoppy experiments. And let us know what you think!