Author: Ray Found

It’s become commonplace for homebrewers to use yeast pitch rate calculators to determine starter volumes in order to ensure healthy fermentation. These tools are based off of pitching rates used in commercial brewing applications, generally accepted to be 0.75 million cells per mL of wort per ˚Plato for ale, double the amount for lager, ostensibly to compensate for the slower activity associated with cooler fermentation temperatures. This model encourages the use of starters to establish a larger amount of viable yeast cells, which usually involves producing the starter 24-48 hours before pitching.

However, another purported benefit of starters is the impact they have on vitality, which can briefly be described as a combination of yeast health and activity level. By agitating a starter regularly, whether via shaking or stir plate, the starter is constantly oxygenated, allowing the yeast to build sterol reserves critical for reproduction and cell wall development, among other things.

I’ve long been curious about this topic. In my own experience, beers pitched with yeast from a starter always show signs of fermentation activity faster, ferment more vigorously, and finish sooner than those pitched with a single vial/pack. Why? I’ve always assumed, based off of what I’ve read, that higher cell counts were responsible for this stuff. Perhaps there’s something else to it?

While working on the first water chemistry xBmt, Marshall had a back-and-forth with co-author of Water: A Comprehensive Guide for Brewers, Colin Kaminski, that moved from water to other topics, including yeast. Colin shared the following information:

Coors England developed an amazing method that is perfect for homebrewers to steal. Take a stir plate and make a starter. Add yeast and 10˚P wort [1.040 SG]. Aerate for 4 hours. At the end of 4 hours pitch into the wort. Do not aerate the batch. This maximizes “vitality.” Vitality is the most difficult to measure and important parameter in yeast. A standard starter is fermented out and then re-pitched. This [a vitality starter] uses continuous air and only allows the starter to spin for 4 hours. No alcohol is produced. The yeast respires but does not enter fermentation until after it’s pitched into the wort.

Marshall asked specifically about viable cell counts, which Colin explained will remain unchanged while vitality will be nearly 100%. I was intrigued and excited to put this one to the test.

| PURPOSE |

To evaluate the differences between a conventional yeast starter made to increase viable cell count and a starter produced a few hours pre-pitch to increase yeast vitality when used to ferment a split-batch of the same wort.

| METHOD |

To test the merits of this vitality idea, I decided to make a reasonably high-gravity beer for this xBmt. With my lupulin supply running low, I reworked my favorite MACC IPA recipe to be a DIPA through specialty malt reductions and the additions of simple sugar. It basically named itself…

Big MACC DIPA

Batch Size Boil Time IBU SRM OG FG ABV 11 gal 60 min 130 6.9 1.075 SG 1.010 SG 8.6 %

Fermentables

Name Amount % Domestic 2-Row 28 lbs 1 oz 80.6 Munich (10L) 4 lbs 9 oz 13.1 Gambrinus Honey Malt 11 oz 2.0 Sucrose 1 lb 8 oz 4.3

Hops

Name Amt/IBU Time Use Form Alpha % Magnum 63 IBU First Wort Addition FWH Pellet 12.6 Mosaic 60 g/11 IBU Flameout w/ 20 min stand Boil Pellet 11.7 Centennial 120 g/19 IBU Flameout w/ 20 min stand Boil Pellet 10.2 Citra 190g/37 IBU Flameout w/ 20 min stand Boil Cone 13.9 Amarillo 56 g Dryhop 2-5 Days Dry Pellet 8.8 Mosaic 60 g Dryhop 2-5 Days Dry Pellet 11.7 Centennial 66 g Dryhop 2-5 Days Dry Pellet 10.2 Citra 150g Dryhop 2-5 Days Dry Pellet 13.9

Yeast

Name Lab Attenuation Ferm Temp California Ale Yeast White Labs 001 85.8% 66°F

I am completely sold on this hop combination, to the point I am worried I am stuck in a bit of a rut with it. A delicious, fruity rut. Anyway, for this batch, I started with 2 vials from the same production lot.

Using my preferred calculator, I determined the conventional starter batch would need to be 1.8L, which I overbuilt a bit to harvest some for future use. About 42 hours prior to pitching, I pitched 1 of the yeast vials into a flask of boiled and chilled wort.

After spinning for about 32 hours, I moved the flask to the fridge to cold crash. Per my normal process, the starter beer was decanted and the flask returned to the stir plate on brew day.

While my strike water was heating in the garage, I made a 500 mL starter, hit it with the other vial of yeast, then placed it on my lego stir plate (build instructions to come) where it remained until the wort was to receive it.

It was a rather uneventful brew day. The mash settled in nicely at my target of 150˚F, where it sat for about an hour before running off.

The sweet wort met a heap of Magnum hops in the kettle, enough to impart a calculated 65 IBU.

This batch reminded why I hate whole cone hops– 190 grams of Citra required 2 huge bags, without which my valve would clog. It looked like loaves of bread going into my wort. One of my side goals for this xBmt was to use up all of my Citra whole cone hops that I’d been avoiding for that last couple months. Mission accomplished.

I quickly chilled the wort with my Hydra IC to 75˚F, about 7˚F above the temperature of my groundwater.

I then filled two 6 gallon PET carboys and placed them in my fermentation chamber to finish chilling. A few hours later, both worts were sitting at my 64˚F target pitch temp and the yeasts were pitched. In stark contrast to the first pitch rate xBmt, both the conventional starter and vitality beers were showing signs of active fermentation just 7 hours in. They were roaring along by the next morning.

Throughout the course of fermentation, I never observed any differences. Both had reached 1.013 SG after a week of fermentation and signs of activity were rapidly dwindling. I added a massive dry-hop charge to each carboy at this point.

A hydrometer measurement 2 days later revealed both beers had reached my target FG of 1.010. I cold crashed, fined with gelatin, then packaged these beers and put them in my keezer to carbonate.

| RESULTS |

The majority of the data for this xBmt was gathered at a BeerMe Brew Club meeting held at Skyland Ale Works. A huge thanks to our hosts and everyone from the club who participated!

The tasting panel consisted of 17 participants including provisional BJCP judges, experienced homebrewers, and enthusiastic craft beer nerds. Each taster was blindly presented with 2 beers from the conventional starter batch and 1 from the vitality then asked to identify the unique sample. In order achieve statistical significance given this sample size, 10 tasters (p<0.05) would have had to correctly identify the odd-beer-out, while only 6 (p=0.86) were capable of doing so, a result consistent with chance.

My Impressions: I never actually triangle tested myself on this one, but in multiple side-by-side comparisons, I failed to reliably ascertain any differences. On the other hand, when Marshall stopped by with friends Aaron and Matt on their trek to NHC, all 3 got it right, which admittedly gave me pause. Matt and Aaron were included in the results since they were blind to the nature of the xBmt, Marshall obviously wasn’t. Still, even with their correct responses, 6/17 isn’t remotely close to significance. My hunch– if served blind multiple times, my ability to pick the different beer would be equally as consistent with chance as the participant panel.

Hey, Marshall here, I wanted to chime to give my impressions since I got to try these beers. For what it’s worth, my guess during the triangle test was, well, just that- a guess. The beers tasted exactly the same to me, I doubt I’d be able to reliably identify the odd-beer-out over multiple triangle tests either. Also, if you’re looking for a tasty IIPA recipe, holy shit, this beer was delicious! I might consider fermenting it with TYB Vermont Ale or WLP090 for fun, but it’s money as is. Cheers!

| DISCUSSION |

I am not terribly shocked by these results and didn’t really expect there to be a significant difference given the results of the first pitch rate xBmt. What I was surprised by was how both fermentations appeared to be effectively identical. I wondered about the possibility the conventional starter didn’t produce as many yeast cells as the calculator predicted, meaning it had a similar cell count as the vitality starter. This seems highly unlikely given what we know about yeast propagation, which leads me to believe the broader interpretation we’ve intended to test in this xBmt deserves some consideration– yeast vitality may be as, if not more, critical than high amounts of viable cells. Something is going on here. Of course, one test is obviously far from conclusive in this manner and the usual caveats about this being a single data point still hold. But the fact these results corroborate those from Coors England lends credence to the idea that healthy starters may not necessarily require more than a few hours on a stir plate.

So, as long as vitality is increased, cell count doesn’t matter– I can pitch an old ass vial of 10% viable yeast into a starter, spin it a few hours, and all will be fine!

Ehh, probably not. Although, at this point, I am comfortable accepting that cell count isn’t the only metric by which we should be evaluating yeast pitch and, personally, I’ll be less inclined to delay brewing because I failed to make a starter in time. This seems like a practical solution for those who, like me, are limited in the times they get to brew, making the spur-of-the-moment brew day using my favorites liquid yeasts a much more viable option.

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| Read More |

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List of completed exBEERiments

How-to: Harvest yeast from starters

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