The Next Generation: Better Viability

Category : Technical
Date : June 12, 2023
Author : Dr. Chris White

From the beginning, White Labs has focused on high cell counts, high viability, and high strain diversity.  In 1995, we coined the term “pitchable” as a way to bring a new type of liquid yeast into homebrewing and integrated into our strain numbers (WLP = White Labs Pitchable). The term ‘starters’ originated before White Labs, and was commonplace among homebrewers because liquid yeast culture packages designed to pitch into wort at ranges over 1 million cells/mL did not yet exist. As a result, it has evolved into a fascinating effort to obtain the best pitching rates for different beer styles.

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Still want to make a yeast starter? Click here for a quick 101!

Knowing how much yeast is needed in every case can be confusing and complex.  This is why many homebrewers turn to online pitching rate calculators to help determine how much yeast is needed by strain, beer parameters, and yeast supplier brands. There are many pitching rate calculators on the web today, such as MrMalty, BeerSmith, Brewer’s Friend, and they are great tools that have helped homebrewers create the best-tasting beer. One of the unique tools that was first introduced by MrMalty was a culture viability value. You can enter the yeast packaging date, and the calculator provides you with a viability number that will be utilized in the calculation. Most online calculators are based on similar formulas.
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One major difference with these early studies is that those estimators were based on other supplier cultures at the time, not White Labs Yeast.  Since yeast is a living organism affected by thousands of variables, remember that this is very much an estimate. The only way to truly know the viability of any yeast culture is to use a microscope or other automated, expensive pieces of equipment and sound scientific techniques. The viability estimators are useful because they are based on packaged yeast and time/shelf-life studies.

"The only way to truly know the viability of any yeast culture is to use a microscope or other automated, expensive pieces of equipment and sound scientific techniques."

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I was asked by another liquid yeast company's employee in 1998, “How are your viabilities so high?” As a fledgling homebrewer and science post-doc, it was important to me to grow and use yeast that was the right cell concentration with better viability and without the need to make a starter.  We focused on small batches to make freshly packaged yeast daily and grew them patiently over 3 weeks to create the best plump cells possible at every stage. This gave us a much higher viability over time than other producers. Since the late 90s, we have continued to push the boundaries of liquid yeast viabilities, taking into account worldwide delivery logistics, and....we achieved the next milestone with the release of PurePitch yeast in 2014 to produce even better yeast!  


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PurePitch is the same great collection of strains propagated in a novel, patented process called FlexCell. Instead of stainless steel vessels, yeast is grown and collected in the same film, reducing exposure to potential contaminants. It’s a more expensive way of making yeast, but it resulted in a marked improvement in cell physiology and longer-lasting viability.

This improved our already-productive propagation for 2 main reasons:
  1. Heat-sealing the yeast inside the film for packaging created very little oxygen pick-up (compared to filling a bottle, for example). Oxygen lowers viability as yeast consumes it for the beginning lag phase and breaks down the stored glycogen that is so important for long-term storage.
  2. The film itself was created to release CO2 so it is not trapped inside the yeast package, and CO2 lowers viability because it is toxic to yeast cells.  
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With PurePitch Next Generation released to homebrewers in 2022, we have further improved the film, allowing more efficient CO2 gas transfer through a fused bi-layer film., Think of the yeast side as a soft, permeable layer while the outside film creates a racing glove grip. PurePitch Next Generation is also constructed with a thinner film, so it reduces our plastic use by 40%, supporting our strive for better sustainability.

"PurePitch Next Generation is also constructed with a thinner film, so it reduces our plastic use by 40%, supporting our strive better sustainability."

Along with this new technology, we have continued to evolve the White Labs estimated yeast viability calculator which we developed over time using data collected from all of our strains over the last 10 years. This large amount of data gives us great statistics for our packaging viability. This number can be plugged into any Pitch Rate calculator, giving you the best recommendation for how much yeast to use or what kind of starter to make. 


To find our estimated yeast viability calculator scan our QR Code on PurePitch Next Generation packaging or enter the lot under the QC tab on
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No matter how large the homebrew package gets today, most pitching rate calculators advise a starter to achieve a certain cell count. PurePitch Next Generation was developed to pitch directly without a starter for 5 gal/20L at 7.5 million cells per mL, a commercially popular ale pitching rate. Yes, we say starters are great, but we wanted to ensure a more precise cell count for everybody, which means a more controlled beer fermentation and overall beer flavor.