Author: Marshall Schott

Fermentation is the seemingly magical, though entirely scientifically explainable, process that turns the wort brewers make into delicious beer. The microorganism responsible for this wonderful conversion is yeast, a single celled fungi that, like all living organisms, work better when provided an optimal environment.

Brewers have adopted various strategies to ensure their yeast are well taken care of including propagation in starters and precisely controlling the temperature throughout fermentation. Another common method said to further reduce the risk of problematic fermentations involves the use of yeast nutrient, a common one of which is produced by Wyeast, who makes the following claim:

A wort that is nutrient-deficient, or which has adequate nutrients but limited bioavailability to the cells, can experience inhibited yeast growth, disrupted or incomplete fermentations, inconsistent attenuation rates from batch to batch, and diminished cell viability.

I’m aware of brewers who use such nutrients as a matter of course, some who dose each batch of beer they make as a better-safe-than-sorry measure, while others contend it has some positive impact on fermentation and even finished beer quality. In the nearly 15 years I’ve been brewing, I’ve never once used yeast nutrient, as I never saw a need. However, after dosing a recent batch of hard cider with nutrient and noticing a fairly drastic reduction in lag, I became curious as to the impact it might have on beer and put it to the test!

| PURPOSE |

To evaluate the differences between a beer produced using yeast nutrient and the same beer that received no yeast nutrient.

| METHODS |

In the hopes of creating a relatively stressful fermentation environment, I opted to brew a cool fermented lager that was direct pitched and went with an adapted version of my May The Schwarzbier With You recipe.

Kräftig

Recipe Details Batch Size Boil Time IBU SRM Est. OG Est. FG ABV 5.5 gal 60 min 26.3 IBUs 26.1 SRM 1.053 1.014 5.2 % Actuals 1.053 1.012 5.4 % Fermentables Name Amount % Lamonta American-style Pale Malt (Mecca Grade) 4 lbs 36.78 Pelton Pilsner-style Malt (Mecca Grade) 3.75 lbs 34.48 Metolius Munich-style Malt (Mecca Grade) 2 lbs 18.39 Gladfield Light Chocolate Malt 12 oz 6.9 Caramel/Crystal Malt - 15L 6 oz 3.45 Hops Name Amount Time Use Form Alpha % Horizon 11 g 60 min First Wort Pellet 14.1 Tettnang 31 g 15 min Boil Pellet 3.5 Yeast Name Lab Attenuation Temperature Harvest (L17) Imperial Yeast 72% 50°F - 60°F Notes Water Profile: Ca 71 | Mg 1 | Na 10 | SO4 100 | Cl 50 Download Download this recipe's BeerXML file

I prepared for this 10 gallon no sparge brew by collecting the full volume of filtered water in my mash tun a day ahead of time.

With the water collected, I weighed out and milled the grain.

I placed my heat stick in the water and set the timer to turn on a couple hours before I started brewing the next day.

The next morning, I was greeted with perfectly heated strike water, into which I incorporated the grains using my large doughball buster.

A check of the mash temperature showed I was close enough to my 152°F/67°C target.

I let the mash rest for 60 minutes, gently stirring periodically to improve efficiency, after which I collected the sweet wort in my trusty graduated bucket.

After transferring the wort to my kettle, I brought it up to a boil and added hops per the recipe.

At the completion of the 60 minute boil, I quickly chilled the wort to slightly warmer than my groundwater temperature.

A refractometer reading showed the wort was smack on my target OG.

Equal amounts of wort were racked to separate sanitized Brew Buckets.

The filled fermentors were placed in my chamber to finish chilling, the wort at this point was 74°F/23°C. I then proceeded with preparing the yeast nutrient for one batch per the recommended method of dissolving a measured amount of the powdery substance in hot water. To keep things as equal as possible between the batches, I added an identical amount of hot water sans nutrient to the other batch.

I left the worts alone for a few hours to finish chilling before returning to direct pitch a single pack of Imperial Yeast L17 Harvest into each batch.

The following morning, approximately 12 hours post-pitch, I noticed airlock activity in both batches, indicating minimal difference in lag. I let the beers ferment at 55°F/13°C while I vacationed with my family and opted to skip any temperature increases.

With neither beer showing signs of fermentation activity after 15 days, I took hydrometer measurements indicating both had achieved the exact same FG.

I replaced the airlocks with CO2 filled BrüLoonLocks before reducing the temperature in my chamber to 32°F/0°C for cold crashing.

Curious if yeast nutrient might have an impact on appearance, I decided to skip my regular gelatin fining process and kegged the beers after 2 days. The filled kegs were placed in my keezer, burst carbonated, and left to lager for 2 weeks before they were ready to serve to tasters.

| RESULTS |

A total of 21 people of varying levels of experience participated in this xBmt. Each participant was served 2 samples of the beer made without yeast nutrient and 1 sample of the beer made with yeast nutrient in different colored opaque cups then asked to identify the unique sample. At this sample size, 12 tasters (p<0.05) would have had to identify the unique sample in order to reach statistical significance, though only 8 (p=0.40) made the accurate selection, indicating participants in this xBmt were unable to reliably distinguish a Schwarzbier made using yeast nutrient from one made without the use of yeast nutrient.

My Impressions: As usual, I began sampling these soon after getting them carbonated and, even in my non-blind side-by-side evaluations, I was unable to tell them apart. Needless to say, my performance on semi-blind triangle tests was completely inconsistent, I guessed the odd-beer-out in 2 out of 7 attempts. As for the beer, I’ve got to say, this Schwarzbier hit the goddamn spot! Even after all these years, I continue to be reminded that simplification of recipes often results in good outcomes, which is certainly the case for this slightly adapted version of a beer I’ve made many times before.

| DISCUSSION |

It makes sense that by supplying yeast with nutrients, they’ll perform better during fermentation in a way that could ultimately have a positive impact on the finished beer. This seems even more plausible when the yeast is forced to work in relatively stressful conditions, such as those caused by a cool fermentation temperature and pitching direct without propagation in a starter. Interestingly, not only were blind participants unable to reliably tell apart a cool fermented Schwarzbier made with yeast nutrient from one made without nutrient, but no differences in fermentation were observed either, suggesting the yeast nutrient had little if any impact on the beer.

Considering the hundreds of batches of good beer I’ve made without yeast nutrient, these results did little to convince me to change my current practices. However, as easy as it’d be for me to write-off the potential benefits of using yeast nutrient altogether, I’m not quite ready make that leap. Not only did this xBmt focus on one specific brand of yeast nutrient, of which there are many, but the lack of a perceptible difference may not necessarily be a function of the yeast nutrient. For example, the yeast used to ferment both beers was very fresh, which could have mitigated the need for nutrients despite the somewhat stressful environment.

Overall, while I may not integrate yeast nutrient into my standard brewing routine, I can understand why some might opt to use it regularly purely as a way to help protect against problematic fermentations. Given the reduced lag time I observed when I used nutrient in a recent batch of hard cider, it’s clear to me it does something, and I look forward to seeing the impact it has when used in even more stressful conditions such as a high OG beer.

If you have any thoughts about this xBmt, please do not hesitate to share in the comments section below!

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