Author: Cade Jobe

One of the keys to making consistently good beer is to ensure consistently good fermentation practices, which for many brewers involves using various nutrients to encourage solid yeast performance. Viewed as being one of the most important nutrients, zinc is readily available for purchase and generally gets added to the wort just before pitching the yeast.

Zinc is a co-factor for certain enzymes that assist with yeast growth and metabolism. Even at relatively low concentrations (0.2-2.0 ppm), zinc is said to have a noticeable impact on fermentation by allowing the yeast to work more efficiently during the growth phase, resulting in a quicker start and healthier fermentation, which ultimately leads to a cleaner tasting beer. While too much zinc can inhibit yeast growth, usage rates at the higher end of the recommended range are also believed to contribute to beer foam stability.

I’ve used a few different types of yeast nutrients over the years, though I hadn’t really considered zinc until a recent episode of the Masters Brewers Podcast. Interested to see what kind of impact it might have on my beer, I designed an xBmt to test it out for myself.

| PURPOSE |

To evaluate the differences between beers fermented with and without a zinc addition.

| METHODS |

With the goal of maximizing any perceptible differences caused by the variable, I went with a relatively high OG Helles Bock for this xBmt.

No Good Keister

Recipe Details Batch Size Boil Time IBU SRM Est. OG Est. FG ABV 5.2 gal 60 min 25.0 IBUs 6.7 SRM 1.070 1.011 7.8 % Actuals 1.07 1.01 8.0 % Fermentables Name Amount % Pilsner (2 Row) Ger 12.75 lbs 91.89 Honey Malt 1.125 lbs 8.11 Hops Name Amount Time Use Form Alpha % Hallertau Magnum 14 g 60 min Boil Pellet 14 Tettnang 14 g 5 min Boil Pellet 4.5 Yeast Name Lab Attenuation Temperature Harvest (L17) Imperial Yeast 72% 50°F - 60°F Notes Water Profile: Ca 56 | Mg 19 | Na 38 | SO4 47 | Cl 64 Download Download this recipe's BeerXML file

A couple of days prior to brewing, I made a large starter of Imperial Yeast L17 Harvest (using leftover dark malt extract) that would later be split.

I started off my brew day by collecting the proper volume of water for a 10 gallon/38 liter batch, adjusting it to my desired profile, then lighting the flame under the kettle.

While waiting on the water to warm, I weighed out and milled the grain.

Once the water was appropriately heated, I incorporated the grains before checking the mash temperature– slightly lower than expected, but nothing I was worried about.

During the mash rest, I measured out the kettle hop additions.

When the 60 minute mash was complete, I sparged to collect the target pre-boil volume then brought the wort to a boil.

Following the 60 minute boil, I quickly chilled the wort with my IC before taking a hydrometer measurement it had hit my target OG.

Identical volumes of wort were racked to separate Brew Buckets that I placed next to each other in my fermentation chamber. After determining the amount of zinc required to achieve 2 ppm, I weighed it out and added it to one batch.

At this point, I evenly divided the yeast starter between two jars then pitched one into either batch.

The beer was left to ferment at 54°F/12°C and I noticed the beer with zinc took slightly longer to show signs of activity than the non-zinc beer. After 7 days, I raised the temperature to 66°F/19°C and left them alone for another 10 days before taking hydrometer measurements confirming both beers had reached the same FG.

I reduced the temperature in the chamber to 38°F/3°C for an overnight cold crash, after which I pressure transferred each beer to separate sanitized kegs.

The filled kegs were placed in my keezer, burst carbonated, then left to condition for two weeks before I began serving them to participants.

| RESULTS |

A total of 15 people of varying levels of experience participated in this xBmt. Each participant was served 1 sample of the beer fermented with zinc and 2 samples of the beer fermented without zinc in different colored opaque cups then asked to identify the unique sample. While 9 tasters (p<0.05) would have had to accurately identify the unique sample in order to reach statistical significance, only 4 did (p=0.79), indicating participants in this xBmt were unable to reliably distinguish a pale lager fermented with zinc from one fermented without zinc.

My Impressions: Over the course of a couple weeks, I attempted multiple semi-blind triangle tests. Given what I’d read, I expected there to at least be a difference in mouthfeel between the two beers and even convinced myself that I could tell them apart prior to my own triangle tests. Nope, not even close. Out of 4 attempts, I picked the unique sample 0 times. The beers were indistinguishable to my palate, and thankfully, both tasted great, though a tad too boozy for my tastes.

| DISCUSSION |

Zinc is a nutrient for yeast that helps to facilitate growth and metabolism, but unfortunately it’s not abundantly present in malted barley. It’s for this reason many brewers have taken to adding zinc directly to wort prior to pitching yeast, the goal being to encourage the healthiest fermentation possible in order to ultimately produce the best beer possible. While there’s ample evidence yeast benefit from zinc, the fact tasters in this xBmt were unable to reliably distinguish a Helles Bock fermented with zinc from one fermented without it suggests it may not have much of an impact on perceptible characteristics.

It’s important to note that trace amounts of zinc are present in malted barley, and it’s possible even this small amount is enough to catalyze the enzymes used during yeast growth and metabolism, which would make any additional zinc unnecessary. Another possible explanation for these results is that the beers were in fact different, but the delta was too small for people to detect it. Indeed, my own experience with these beers was influenced heavily by what I’d read about the impact zinc can have on mouthfeel and foam, which unsurprisingly were the only areas I initially thought I was able to perceive a difference.

As a brewer who is interested in doing whatever I can to produce the best beer possible, I’m certainly open to using zinc if it has a positive impact. While I require more data before I’m willing to commit to a certain perspective, the results of this xBmt along with my own inability to distinguish the beers leaves me comfortable claiming that adding zinc at yeast pitch isn’t necessarily required to make good beer.

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

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