Smack-Pack Activator System™ for Home Enthusiasts


Wyeast Premium Liquid Yeast has been the choice of professional winemakers, cidermakers, meadmakers, and more since 1986, and we have offered the same quality and diversity of cultures to home enthusiasts since then, too, in our innovative and one-of-a-kind product: the Smack-Pack Activator System™. 

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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 you pitch. Activator™ packages include a sterile liquid nutrient pouch that, when smacked, releases its contents into the yeast slurry. The available 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. The Smack-Pack Activator System™ provides optimum conditions for storage, while providing proof of healthy yeast ready for inoculation of must, juice, wort, or seed mash.


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 healthy 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 6 gallons (22 L) of must, juice, wort, or seed mash - the same pitch rate used by professionals. We recommend inoculating at warm temperatures (70-75 °F, 21-24 °C), waiting for signs of fermentation, and then adjusting to the desired temperature. For higher gravities, we recommend increasing this pitching rate. This can be achieved by pitching additional Activator™ packages or by making a starter culture. For additional gravity 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. Shake well, sanitize package, open and pour the Activator™ into 6 gallons (22 L) of well-aerated or oxygenated juice, must, or wort at 65-72 °F (18-22 °C). Maintain temperature until fermentation is evident by CO₂ bubble formation, bubbling airlock or foaming on top of must, juice, or wort. For Saké, add to seed mash (Koji/steamed rice/water) to produce your saké starter (Shobu or Moto).
  6. Adjust to desired fermentation temperature. For more information on temperature selection, visit our Strains sections for WINEMAKING, CIDERMAKING, MEADMAKING, or SAKÉ BREWING 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 the 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.

We think you’ll agree our unique “Smack Pack” is preferable to all other liquid yeast packaging options to assure the success of your fermentations.