Yeast Specifications

We pride ourselves on accurate and consistent package cell counts every pitch, every time!

You can find our product specification data sheets here.

Ale & Lager Culture Cell Counts

Imperial Yeast packages slurry with a specification of 1.29 x 10¹² total viable cells per Verified Unit (VU). This is true for every pitch every time. 

In an effort to save our customers shipping costs, Imperial Yeast customizes each pitch by concentrating slurries to deliver the same number of total cells (1.29 x 10¹²) in the least amount of liquid.   Each order and amount of concentration is strain and batch dependent.  Each unit of 1.29 x 10¹² total cells is referred to as a “Verified Unit.” What that means is the yeast slurry volume/weight may change, but the total cell count will always be what you ordered.

Pitch Rates

As a brewer, it is important to decide which pitch rates perform best for your brewery and how to consistently quantify them from batch to batch. Imperial Yeast offers many tools, including our brewing calculators, to help you decide what is best for you and how to optimize pitch rates for your yeast management program. 

Pitch rates are a major driving force in the consistency and quality of your beer.  They play an important role in the health and growth of yeast cells, fermentation kinetics, and flavor and aroma outcomes. Managing your pitch rate ensures repeatable results from batch to batch.

Why Pitch Rates Matter

• Under-pitching risks: 
• Slow or stalled fermentations
• Incomplete attenuation
• Extended VDK (diacetyl) reduction times
• Poor harvests
• Increased off flavors
• Potential over-carbonation in packaged beer.
• Over-pitching risks: 
• Reduced ester profiles
• Increased sulfur compounds
• Decreased new, healthy cell growth
• Over-pitching leaves a higher percentage of older, less healthy cells for subsequent generations, leading to sluggish and inconsistent fermentations.

Standard Industry Recommendations

• Ales (≥ 60°F): 0.75 million cells/mL/ºP
• Lagers (< 60°F): 1.0 - 2.0 million cells/mL/ºP

The Imperial Yeast Verified Unit (VU)

Every Imperial Yeast commercial pitch is delivered as a Verified Unit (VU), guaranteeing a specific number of viable yeast cells in each unit, regardless of slurry volume.

• Cell Count per VU: 1.29 x 10¹² (1.29 trillion) viable yeast cells.
• Standard Pitch Rate: Pitching 1 VU per barrel of 14.5ºP wort delivers a pitch rate of 11 million cells/mL. When we divide 11 by 14.5ºP we get 0.75, which is the standard pitch rate for an ale.

Oxygenation

In addition to pitch rates and temperature, oxygen has a major effect on the growth and health of yeast cells during fermentation.  Oxygen is required for yeast membrane unsaturated fatty acid (UFA) and sterol synthesis which maintain cell flexibility and permeability, and is critical for cellular transport of energy sources and nutrients.  UFA and sterol content is also the primary factor limiting cell growth.  With each cell doubling, UFA and sterol content is diluted until it reaches a critical point where the cells can no longer divide.  Without proper oxygenation and subsequent UFA/Sterol synthesis, less growth occurs reducing the amount of yeast available to do the work.  This can result in impacts on beer flavor and aroma, extended VDK (diacetyl) reduction times, long fermentation times, stalled or incomplete attenuation, long tank residency, and potential over carbonation in packaged beer. 

To ensure adequate oxygenation, we recommend adding pure oxygen inline through a sintered stainless steel stone during knockout using an Oxygen Flow Meter measuring in liters per minute (LPM).  There should be at least 10 ft. of hose between the oxygen stone and the receiving tank to limit oxygen breakout.  This method allows the brewer to achieve accurate and consistent dissolved oxygen (DO) levels with the delivery of a set amount of oxygen to a specific volume of wort.

By generally accepted brewing industry standards, it is best practice to verify DO levels by using a DO meter like this Portable Dissolved Oxygen Meter to ensure proper oxygenation.  A helpful tool for estimating oxygen flow rates is available online using Imperial Yeast’s  DO Calculator. The recommended levels of dissolved oxygen may vary, but in general, lager strains require ~8-12 ppm, ale strains require ~12-14 ppm, and high-need strains like A38 Juice, require 20-25 ppm. Highly flocculant strains and/or low pitch rates may also benefit from higher levels of dissolved oxygen.

Temperature

Understanding the role that temperature plays in yeast health and fermentation is critical, if we want to create quality beer consistently and maintain happy healthy yeast. 

In addition to pitch rates and oxygen, temperature has a major effect on the growth and health of yeast during fermentation. As a result, fermentation kinetics and the final character of the beer are greatly impacted. Warmer or cooler temperatures during fermentation can increase or decrease yeast’s growth and their rate of growth, the rate of fermentation, the levels of ester and alcohol expression, and influence a plethora of other fermentation by-products. 

In extreme cases, yeast that become too cold may struggle to grow during the lag and log phases and/or flocculate prematurely, resulting in less new healthy yeast cells and poor harvests. Slow, or inhibited growth may also result in sluggish or stalled fermentation, increased VDK (diacetyl) reduction times, and often less ester and alcohol expression.  Yeast that become too hot can experience rapid growth, high levels of stress,  and potentially lower viabilities. Higher temperatures often result in rapid fermentation and VDK reduction times, as well as higher alcohols and esters. 

In order to maintain healthy yeast cell growth and healthy fermentation, temperature, along with pitch rates and oxygen must be in balance.

For more questions regarding pitch rates and other yeast management topics, please see our technical support, or contact techsupport@imperialyeast.com for assistance. Cheers!