An Experiment in Suspension

As I’ve been learning more and more about homebrewing, one thing I’ve read is that if struggling to get a beer to carbonate, you can gently agitate the bottle to put the yeast back in suspension and thus help get it back to work on those unused sugars. I’m also a fan of aging beer, so this idea got me thinking and eventually led to an experiment. If settled yeast normally continues to work on a beer over time, would a beer’s yeast that is continually put back into suspension, thus increasing its efficacy on unused sugars, cause the beer to “rapidly age” or taste as though it were older than it is?

Disclaimer: I am by no means a scientist, but I’m married to one so I feel that my methods were vicariously scientific. I did my best to apply the controls and methodology I vaguely remember from middle school chemistry. I tried my best to be scientific throughout this process, but recognize that this was not done in a lab and that there are plenty of variables outside (and probably inside) my control that I did not account for.

Objective:
Test the effects of consistent yeast resuspension in a finished beer over the course of 1 year.

Methods:
I selected three beers that were bottle-conditioned or had an obvious yeast bed: Boulevard Tank 7 (Farmhouse/Saison), Rush River Double Bubble (DIPA), and Founders Backwoods Bastard (BA Scotch/Wee Heavy). While it is arguable whether each of these styles and/or specific beers are supposed be aged, it should not matter in the spirit of the experiment, which was designed to only assess how the beer changed over time if the yeast was put back into suspension. All beers selected for the experiment were purchased within two weeks of bottling to ensure the experiment began with fresh bottles.

I filled a six-pack holder with two of each beer, where they remained throughout the experiment to ensure that storage methods were consistent. One bottle of each beer was designated a resuspension bottle and marked with an X on the label. The six-pack was stored in my cellar, which is dark and averages 55F.

Each week on a Thursday evening, I would gently overturn the X-marked bottles five times to resuspend the yeast. I did this as delicately as possible to avoid oxidation. The resuspended bottles were then placed back in the six-pack and remain undisturbed until the following week. The control bottles sat untouched throughout the experiment.

After 1 year of weekly resuspension, each beer pair was opened and evaluated against one another. Evaluation criteria were the standard appearance, smell, taste, mouthfeel, overall categories used in BeerAdvocate ratings. The same style glasses were used in order to limit variables.

Observations:
Overall: As the experiment progressed, I noticed that Tank 7 took the longest for the yeast to settle out (3-5 days at first), followed by Double Bubble (2-4 days at first), then Backwoods Bastard (1-3 days at first). As the experiment went on, the yeast settled out more quickly as there were progressively fewer unused sugars available. After 1 year, the yeast beds between the two bottles were markedly different: the resuspension bottle had fine-grained, easily unmoored yeast while the control bottle had large, flocculated yeast chunks that remained anchored.

The color of each beer was largely unchanged by the experiment, so it is not noted in the findings below.

Rush River Double Bubble: much larger head but dissipated more quickly; fruitier and more floral nose; boozier/hotter; rougher, spicier malt profile; lots of honey; more bitter; fruitier with lees mixed in; drier; lighter

Boulevard Tank 7: significantly more carbonation (at least double); more dense head structure with better retention; less floral nose; smoother malt with greater depth and complexity; more molasses, vanilla, caramel, orange, and bread/wheat cracker; less fruity and sweet; slightly more bitter; more balanced; lighter body by deeper flavor; drier

Founders Backwoods Bastard: longer head retention; much creamier, less bourbon and vanilla on nose; smoother, and balanced; more prominent bourbon, vanilla, caramel, fruit, date, fig, vague rye; fuller mouthfeel; NOTE: when the control bottle was opened and carefully poured, all the yeast chunks went into suspension and did not settle out.

Conclusions:
Yeast resuspension predictably increased the head size and carbonation of each beer. It also produced a drier finish with less residual sweetness. Typically the malt profile was smoother and better balanced.

The nose varied in intensity for each beer. It was difficult to discern how individual flavors were affected by
resuspension, but obvious that the profiles of each were different.

Like any aged beer, the resuspended bottles were not necessarily better than the controls, just different. I think I enjoyed the resuspended versions of Tank 7 and Backwoods Bastard more than their counterparts.

Further experimentation:
Less time between resuspensions. Daily resuspension versus weekly could make a difference.
Longer experimentation period. 1 to 3 year durations could produce more drastic end results.
Compare to bottles older than 1 year. Resuspended yeast bottles could be closer to 2 year bottles than 1 year.

I’m open to any questions, discussion, or skepticism. I’d love to hear any scientific perspective or input as well.

 

After she explained to me what that is, that would have been a great way to do it! I could have had two controls and one resuspended, and done a blind taste test of all three. It would probably also help to have someone else try these with me to get more sensory observations. Although doming three bottles of Backwoods Bastard does make for an interesting afternoon.

I know! I wish I had thought of that earlier in the experiment. Had I been more proactive, I probably could have easily traded for some '11 or '12 Backwoods. Ah well, next time.

 

I think I'm going to try this again but go for a longer time with a few more bottles of each beer. I'd probably do controls of different ages and then both daily and weekly resuspension bottles for 1, 2, and 3 years. I'll definitely choose some different styles that will stand up to the longer aging process; likely a barleywine or a Belgian. Originally I picked from whatever was fresh in the cooler at the time and had a visible yeast bed. Plus Backwoods Bastard is way too expensive to use again. I could try a sour or farmhouse with brett, but I don't know if they would explode after a while. I'd be open to suggestions on this.