Liquid Yeast for Brewing


Elevate the quality of your homebrews with Wyeast Premium Liquid Yeast. One-of-a-kind Activator Smack-Packs™ double as a yeast viability test and proven quality control - allowing your craft brewing skills to ascend to new heights.


Wyeast Premium Liquid Yeast has been the choice of professional brewers and craft beverage makers since 1986, and we have offered the same quality and diversity of cultures to homebrewers in since then, too, in our innovative and one-of-a-kind product: the Smack-Pack Activator System™. 

Wyeast Smack-Pack


Why Brew with the Smack-Pack Activator System™?

For over 30 years, the Wyeast Activator™ is the only product that "proofs" the yeast and shortens lag time when it hits your wort. Activator™ packages include a sterile liquid nutrient pouch that, when smacked, releases its contents into the yeast slurry. The available sugars and nutrients initiate the culture’s metabolism which in turn generates CO₂ and causes swelling of the package, serving as a viability and vitality test as well. Although beneficial, cultures do not need to be activated prior to inoculation.


Activator™ Product Information and Usage

Activator™ packages contain a minimum of 100 billion live yeast cells in a liquid slurry. This yeast slurry is packaged in an optimum condition for storage, while maintaining the ability for rapid and complete fermentation. The reliable cell count of all Wyeast yeast ensures that you are pitching the same amount of yeast every time while avoiding the issues that arise with over- and under-pitching. 

One Activator™ package is designed for direct inoculation of 5 gallons (19 L) of standard gravity ale wort - the same pitch rate used by professional brewers. For lagers, we recommend inoculating the wort at warm temperatures (65-72 °F, 18-22 °C), waiting for signs of fermentation, and then adjusting to the desired temperature. Alternatively, for pitching into cold conditions (34-58 °F, 1-14 °C) or higher gravity wort, we recommend increasing this pitching rate. This can be achieved by pitching additional Activator™ packages or by making a starter culture. For additional gravity, temperature, and style pitch rate recommendations, visit our PITCH RATES section.


Instructions for the proper use of Activator™ packages:
  1. Remove Activator from refrigeration (34-40 °F, 1-4 °C) and allow to come to room temperature just prior to use.
  2. To activate, locate and move the inner pouch to a corner. Place this area in palm of one hand and firmly smack the package with the other hand to break the inner nutrient pouch. Confirm the inner pouch is broken. If you do not require proof of activity, proceed to the 5th step and Direct PitchContents of inner pouch do not need to be transferred to your wort when not Activated.
  3. Shake the package well to release the nutrients.
  4. Allow the package to swell for 3-5 hours or more (it is not necessary for this package to fully swell before use) at ambient temperature (approx. 70 °F, 21 °C).
  5. Use sanitizing solution to sanitize the package before opening.
  6. Shake well, open and pour the Activator™ into 5 gallons (19 L) of well-aerated or oxygenated wort up to 1.060 OG at 65-72 °F (18-22 °C). Maintain temperature until fermentation is evident by CO₂ bubble formation, bubbling airlock, or foaming on top of wort. For high gravity or low temperature fermentations, additional yeast may be required.
  7. Adjust to desired fermentation temperature. For more information on temperature selection, visit our YEAST STRAINS section and select the strain being used.

Watch the Smack-Pack Activator System™ How-To video to see the process in action!


Sterile Packaged Product – UV Light Barrier –  Guaranteed 

Keep Refrigerated. Do not freeze.

Best if Used by:

This package performs best when used by the Best if Used By date when stored between 34-40 °F (1-4 °C). Older yeast or yeast that has been exposed to higher or lower temperatures may take longer to become active or swell. 


Product Warranty

Our Product Warranty states that we guarantee the viability of the yeast in our Activator™ packages for a minimum of 6 months assuming that they have been properly shipped, stored and handled. Our superior packaging material provides 100% oxygen barrier and UV light protection making this exceptional guarantee possible. During this guaranteed shelf life, some loss of viability is to be expected. This will vary from one strain to another. Activator™ packages that are within 2 months of the Best if Used By date may require additional time to swell after activation.

Wyeast does not recommend using viability calculation tools to estimate pitching or starter volumes. These tools were not developed with Wyeast and do not accurately reflect the quality of our products.

Activator™ packages will sometimes swell slightly to moderately during shipping, or later while properly stored. This is not an indication of deterioration if the package is within the Best if Used By date and has been properly handled. This is result of trace amounts of nutrients still available at the time packaging, and causes a small amount of culture activity and CO₂ production. Some strains are more prone to this than others.