At first, fermentation was a thriller. We now know that the conversion of fermentable carbohydrates into ethanol and carbon dioxide is completed by Saccharomyces cerevisiae (or Saccharomyces pastorianus if we’re speaking lagers). We additionally know that there’s extra to fermentation then simply alcohol and CO2 — different yeast metabolism byproducts reminiscent of esters, carbonyl compounds, acids, increased alcohols, and sulfur compounds can all contribute to the ultimate taste, aroma, and mouthfeel of beer. Much like altering wort composition or dry hop regimes, altering your yeast pressure or various fermentation parameters is without doubt one of the quickest and best methods to change your beer.

The genetic make-up (genotype) of the yeast pressure used can dictate the categories and portions of those organoleptic compounds (phenotype) — subsequently altering the yeast pressure can vastly have an effect on the sensory attributes of your beer. Nonetheless, altering the yeast pressure isn’t the one strategy to have an effect on a beer’s last sensory. Altering fermentation parameters can be instrumental in honing in on the ultimate taste and aroma of your beer. It is because the atmosphere that your yeast ferments in will have an effect on its metabolism, progress, and general well being. This isn’t to discredit the function that wort composition or hopping regimes have on beer taste and aroma; they play large roles as nicely. 

However, experimenting with yeast strains and the parameters by which it ferments is an effective way for brewers to optimize fermentation flavors. What’s the best strategy to see this in motion? Carry out yeast trials of your individual, after all! 

Yeast trials may be performed comparatively simply with out the necessity of specialised gear. All you’ll want is your wort and a few vessels to ferment in. Relying in your brewing setup, you’ll be able to carry out ferments in something from 5-gallon (19-L) carboys to 1-quart (1-L) Erlenmeyer flasks. I’d suggest maintaining the kind of vessel constant inside an experiment and, after all, sanitation is paramount. So as to decide the affect that the yeast pressure is having in your ferment you’ll want to make sure that the one variable altering is the pressure of yeast getting used. This implies maintaining different components like temperature, pitch-rate, dissolved oxygen (DO) ranges, and many others., the identical.

Experiment with Yeast Strains

You may ask your self when designing a brand new recipe, “How do I do know what yeast to strive”? Take into consideration what sort of attributes you need your beer to have after which analysis the yeast strains that match these traits. When you’ve got your checklist of doable strains then it’s time to conduct an experiment.

Are you trying to make a hazy IPA? Don’t select a brilliant flocculent pressure. Are you searching for a cool saison? Select a excessive phenol-producing pressure. You may be searching for one thing fully out of the blue. Attempt brewing your award-winning pale ale in a break up batch, one fermented with the recipe’s typical pressure and one with a pressure that has somewhat funk like WLP644 (Saccharomyces Bruxellensis Trois). The world is your oyster with regards to selecting strains to experiment with.

One other attention-grabbing experiment you might strive is to carry out dry yeast versus liquid yeast trials. You’d be amazed on the variations that you may detect when it comes to modifications in metabolites. Even issues like readability or head retention, which you may not instantly attribute to a yeast pressure, may be noticeably totally different as a result of yeast’s interplay with wort proteins and hop compounds.

So far as wort goes, you’ll be able to carry out these experiments in any type of medium like an IPA, a stout, or a blonde. Sometimes, when within the lab (I’m a Senior Analysis Scientist at White Labs), I are inclined to make a quite simple all-malt wort with a selected gravity of 1.061 (15 °P) hopped to 25 IBUs with Iso-hop. Sounds interesting, proper? Of coruse, you don’t have to work with something this bland to be able to acquire an understanding of the yeast’s character; you need to have the ability to drink your experiment in any case. Nonetheless, the extra impartial in taste the beer is, the simpler it will likely be to guage the variations in your experiment. So, at house, it’s possible you’ll contemplate brewing a light-weight lager, golden ale, or different model that has a low hopping price and few
specialty grains.

If the totally different yeast strains you’re utilizing in your experiment differ of their optimum fermentation temperature (they need to be in the identical ballpark if you’re selecting between a number of strains for a specific beer model), it’s normally a secure guess to ferment at 68 °F (20 °C) for ales or 54 °F (12 °C) for lagers. Consistency is essential with regards to one of these experimentation, so no matter you select to do, do it the identical each time.

So as to see an experiment utilizing totally different strains on a single wort in motion, we carried out mini ferments at White Labs on a benchtop scale and ran the beer via gasoline chromatography to quantify among the fragrant compounds current. Whereas some compounds don’t change a lot between strains, some compounds like Isoamyl Acetate, an ester that’s usually described as banana, have large variances between strains (Desk 1, above). This experiment was carried out within the lab wort I discussed earlier, nevertheless comparable tendencies must be seen with a extra advanced medium. Bear in mind, this was the very same wort break up into a number of vessels; all fermentation parameters have been managed.

This experiment was carried out to be able to illustrate how these metabolites can differ between strains. You’ll discover that the values for the compounds listed are all totally different throughout strains; no two strains produced the very same quantity of a given metabolite. This knowledge is cool (in my humble opinion) as a result of it validates what we already know from a sensory facet. As an example, esters, that are fruity in aroma, are increased in each the Belgian golden pressure and the hefeweizen pressure — two beer kinds by which esters are a typical descriptor.

Experiment with Fermentation Parameters

One other strategy to conduct yeast trials at house could be to differ fermentation parameters. These are issues like dissolved oxygen ranges, head stress, temperature, pitch-rate, beginning pH, mineral ranges, agitation, and many others. For the sake of brevity, we’ll deal with two of those variables: Fermentation temperature and pitch-rate. Much like our yeast pressure setup mentioned earlier than, you’ll solely need to change one variable at a time to be able to actually see the affect that this variable has on the ultimate sensory of your beer.

Pitch-rate may be altered and performed with very readily at house. Adjusting pitch price will result in totally different quantities of progress in fermentation. This modification in progress will have an effect on the sort and quantity of metabolites produced. Pitching charges will differ relying on the kind of beer you’re producing and the yeast pressure that you simply’re utilizing, however usually talking 0.75–1.5 million cells per milliliter per diploma Plato is really helpful. 

In our yeast lab we use a cell counting setup that permits us to find out the precise variety of cells being added to every fermenter. However, how will you do that at house? 

If you happen to’re pitching immediately from the producer’s yeast packaging (with out a yeast starter) strive including two packets of yeast in the event you usually add one. Most producers will checklist the focus of the yeast on the package deal, so in the event you don’t have a microscope, don’t fret, simply use the knowledge given to you by the producer. The overall rule of thumb is that the upper the pitch price the extra fusel alcohol manufacturing and the decrease the ester content material.1 Bear in mind, the viability of your liquid yeast will lower with age. The quantity of dying is yeast strain- and manufacturer-specific, however an overarching estimate for liquid yeast could be that about 5–10% of the yeast will die every month.

Various fermentation temperature may be performed at house if in case you have fermentation management or with somewhat ingenuity. Arrange your ferments as earlier than, this time solely differ the temperature at which you’re fermenting. You’ll need to guarantee that the temperatures aren’t out of the realm of regular fermentation temperatures. Most strains will include a really helpful fermentation temperature vary. Attempt fermenting on the high and backside of that vary. For many ale strains I’d keep between 61–77 °F (16–25 °C) and most lager strains between 48–59 °F (9–15 °C). Typically talking, the next temperature will enhance the metabolic compounds shaped.1 The impact that temperature has will probably be yeast strain-specific as nicely. Sure yeast strains have the capability to deal with increased fermentation temperatures higher that others and the identical is true for decrease temperatures.

I carried out a trial at White Labs utilizing WLP001 (California Ale) within the aforementioned lab wort at 66 and 75 °F (19 and 24 °C). Curiously, you don’t see a lot distinction between metabolites aside from acetaldehyde (inexperienced apple), which was considerably raised with increased temperatures (Desk 2). Acetaldehyde is taken into account a significant off-flavor in beer, subsequently on this occasion I might conclude that this pressure performs higher at decrease fermentation temperatures.

How you can consider your experiments

Whereas I do know that lots of you’ve got homebrew setups that might make even essentially the most skilled brewer jealous, there’s a good likelihood that almost all of you don’t have a gasoline chromatograph at your disposal. So how do you consider the impact that your yeast trials have had in your last product? A simple and quantifiable metric that you may measure is the pace of fermentation. This entails taking day by day pH and gravity readings to trace the progress of your fermentation. It’s doable that you simply may not discover an enormous sensory distinction between two strains, however one pressure may attain last gravity a full two days earlier than one other and everyone knows time is cash.

In case you are within the quantifiable sensory attributes of your beer, you might ship your experiment to an out of doors lab (like White Labs, nevertheless labs that may carry out these exams are scattered throughout most areas). These providers value a variety of cash relying on what precisely you might be after, however as they’re consultants within the area and have the correct gear, you get outcomes you’ll be able to belief. Otherwise you may be fortunate and have a good friend who works at a college or biotech firm which may be capable of run your samples for you in change for beer, (these are among the greatest buddies to have).

One other straightforward and pleasing strategy to consider your outcomes is to carry out sensory in your last product. This may be performed in additional refined methods than asking your self “is that this good or unhealthy?” (although that may be a legitimate query to ask). Sensory analysis ought to embody 4 points of your beer – taste, aroma, mouthfeel and look. When making an attempt to find out whether or not your experiment in yeast pressure or fermentation parameters causes a noticeable change in sensory, strive organising a sensory take a look at like a duo trio or a triangle take a look at after which recruit some samplers. Particulars of tips on how to arrange these exams may be discovered on-line. Each strategies are straightforward to arrange and can assist you consider whether or not there’s a distinction between your yeast trials. One other technique you might use to guage your trials is to ask your panel (buddies, homebrew membership members, beer judges, and many others.) to rank your beers utilizing a 5-point hedonic scale.

On the subject of performing yeast trails, the most important factor to recollect is to solely change one variable at a time so that you simply get a real understanding of how that variable impacts the ultimate final result of your beer, mead, or cider. In case your system permits for it, strive your experiments at a small scale earlier than ramping as much as bigger ferments. This can assist preserve you from making a bunch of unhealthy beer. Total, experimenting at house may be very pleasing, particularly whenever you get to drink your experiments.


1 Van Laere, S.D.M., Saerens, S.M.G., Verstrepen, Ok.J. et al. Appl Microbiol Biotechnol (2008) 78: 783.