Pitching rate is an important factor in the brewing process. Although not the only variable in clean fermentation, pitching rate plays a key role in lag-time, attenuation, and yeast-derived flavor production. From the brewing literature, “rule-of-thumb” pitching rates are tailored for harvested and re-pitched yeast on the commercial scale. However, when using lab-grown, propagated yeast cultures, often sold in liquid form to homebrewing consumers, these pitching rates are less clear and can be better qualified for small batch brewers. In this series of Small Batch Brewing, I attempt to provide clarity on pitching rates for lab-grade yeast. In particular, I hope to answer this important question: What is a good pitch rate for healthy, lab-grown yeast when pitched directly into wort without a starter? In Part 1 (linked here), I provide a short introduction to pitching rate, lab-grade yeast cultures, and their effect on fermentation. In Part 2 (this post), I review the literature and yeast manufacturers guidelines, narrowing in on a good pitch rate for lab-grown yeast. In Parts 3 and 4 (later posts), I explore the considerations of these pitching rates for small batch brewing; in particular, brewers looking to direct pitch liquid, lab-grade cultures. As always, cheers, and happy brewing!
What does the brewing literature say about pitching rates?
As often in brewing, it depends who you ask. A professional brewer “rule-of-thumb” pitch rate for average gravity ales and lagers is 1 million cells/ml/°Plato. However, as a “rule-of-thumb”, this pitching rate applies to harvested and re-pitched yeast without propagation. A more specific pitching rate can be found in George Fix’s Principles of Brewing Science. Here, he recommends separate pitching rates for ale and lagers of 0.75 and 1.5 million cells/ml/°Plato, respectively. Although more nuanced for ale and lager yeast strains, this rate still pertains to re-pitched yeast. Thus, both “rule-of-thumb” and Dr. Fix’s pitching rate can be seen as upper-bounds for healthy lab grade liquid yeast.
A more focused recommendation for lab-grown pitching rate comes from Yeast: A Practical Guide to Beer Fermentation. On page 121, it states:
“When pitching a fresh, laboratory culture grown with aeration and good nutrition, a brewer can use up to 50 percent lower pitching rate.”
This is particularly interesting. Given proper sanitization, oxygenation, wort nutrition and fermentation temperature, it would seem lab-grade yeast may need significantly less pitch rate. Although a solid recommendation from Jamil and Dr. White, it would be best to identity what yeast manufacturers recommend before using this rate.
What do lab grade yeast manufacturers suggest to homebrewers on pitching rate?
It’s clear from both Wyeast and White Labs, the two primary liquid yeast manufacturers, that pitch rate for lab-grade yeast is in agreement with Yeast, in particular, that a lower pitching rate is appropriate.
From Wyeast: Looking through their website technical data, they are surprisingly specific on the recommended “direct-pitch” rates with their lab-grown yeast. However, rather unpleasantly, their recommendations use gravity independent pitching rates. For standard gravity ale and warm pitch lager, below 1.060 starting gravity, Wyeast recommends a volumetric pitching rate of 6 million/mil which translates to a pitching rate range of 0.40-0.60 millions cells/ml/°Plato. This is a good agreement with Yeast which recommended pitching rates roughly half of Dr. Fix’s pitching rate at 0.375 million cells/ml/°Plato for ales and warm-pitch lagers. More specifically, quoted directly from the Wyeast:
The quantity of yeast needed varies for style of beer and yeast strain to be used. Original gravity and temperature are both also major factors. When the original gravity increases, the amount of yeast added also needs to increase. For lagers that are fermenting cold, the pitch rate needs to increase.
The following chart outlines recommended pitch rates based on specific wort and fermentation conditions. Pitch rates are valid for both direct pitching Wyeast products and for pitching with a starter culture of Wyeast products
From White Labs: Overall, they are not as specific on recommended pitching rates for homebrewers as Wyeast. However, in lieu of any particular recommendation, they repeating the core sentiment from Yeast on lab-grade liquid yeast. Quoted directly from the White Labs pitching rate link:
Most professional breweries re-pitch their yeast because they have the fermentor design and facilities to reuse yeast. So most brewery pitches are actually re-pitches, and only 2-10% of brewery pitchings are using freshly propagated yeast. One of the main sources of contamination in a brewery is the pitching yeast. So in order to out-compete other organisms, large quantities of yeast must be pitched. When propagated by a professional yeast laboratory, the yeast is grown under sterile conditions, sterile oxygen and special nutrients are used to improve cell construction and performance. This does not occur in a brewery, so numbers they use to “pitch” take into account the inadequacy of their brewers yeast. The yeast is also unhealthy due to prolonged growth without oxygen and nutrients. In addition, brewers yeast will always contain some contaminants that need to be out-grown, and 1 million cells per ml per degree Plato has been found to be the best marriage of high pitching rates and no negative flavor effects. Liquid yeast grown by a professional laboratory should have no contaminants, so out competing contaminants found in the pitching yeast is not a concern.
Essentially the “rule-of thumb” is a perfectly adequate pitching rate, especially for pro brewers harvesting and re-pitching yeast. However, using a lab-grown yeast, the homebrewer likely does not need this rate especially when pitched into well-aerated, nutrient-sufficient wort. Also, given that Dr. Chris White, co-author of Yeast is also founder of White Labs, it’s likely that it’s in agreement with a ~50% reduced pitch rate when using a lab-grade pitch rate.
Based on all this reading, what is a recommended pitch rate for direct pitching of lab grade liquid yeast?
As a starting point for a new recipe, using fresh, healthy lab-grade yeast, a pitching rate of ~0.50 million cells/ml/°Plato is appropriate in conjunction with proper brewing practices. For cold pitch ales and lagers, an increased the pitching rate of ~1.0 million cells/ml/°Plato is also a good starting point. For big beers, these pitching rates may need to be increased appropriately, along with increased oxygen dosing, wort nutrition, etc. From my experience (for what it’s worth), these direct pitching rate work very well, producing nice, clean beer without detectable yeast-derived off-flavors on the palette. Additionally, noticeable fermentation begins within 12 hours of pitching and high krausen 24 hours after pitching, a desired fermentation cycle when using appropriate pitching rates. For these reasons, I use these pitching rates when direct pitching lab-grade yeast in my apartment brewing. I diverge slightly from Wyeast recommendations in that I like to maintain pitching ratio ratio in million cell/ml/°Plato as opposed to million cell/ml. For those curious, I recently used these pitching rates on the Session Helles. Using a fresh vial in 4 gallons of 1.040 wort, warm-pitched and slowly chilled to lager temperatures, this pitching rate produced a fine beer without detectable off-flavors.
Next Post in Series: Part 3, Considerations for Small Batch Brewers
In the next part of the lab-grade pitching rate series, I apply the above pitching rate recommendations to small batch brewing (1-5 gallon batches), in particular, categorizing pitch rate, yeast age, starting gravity, and batch size as key factors.
What are your thoughts on pitching rates of lab-grown yeast? Leave your brewing experiences in the comment section below. Cheers, and happy brewing!
Post Sources and Additional Links for Pitching Rate Info
Wyeast on Pitching Rates: https://www.wyeastlab.com/hb_pitchrates.cfm
White Labs of Lab-grade Pitching Rates: http://www.whitelabs.com/faq/beer-amateur/pitching-rates
Yeast: A Practical Guide to Beer Fermentation: http://www.brewerspublications.com/books/yeast-the-practical-guide-to-beer-fermentation/
Talking Yeast with Wyeast from Northern Brewer: https://www.youtube.com/watch?v=lEkwp_2Yezo&list=PLgOVeEqw5B8MkKdSZVKMHWdWpxNqn3uRv
BYO: The Latest on Liquid Yeast: https://byo.com/stories/item/1487-the-latest-on-liquid-yeast
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