Smack-Pack Activator System™

Wyeast Laboratories, Inc. Activator™ packages are designed for direct inoculation of 6 gallons of must or juice.

The Smack Pack System™ provides optimum conditions for storage, while providing proof of healthy yeast ready for inoculation of must, juice, wort or seed mash.

Activator™ packages include sterile liquid nutrient pouch that, when “smacked”, releases its contents into the yeast slurry and “activates” the package. The available nutrients initiate the culture’s metabolism which in turn generates CO₂ and causes swelling of the package. This process will reduce lag times by preparing the yeast for a healthy fermentation prior to inoculation. Activation also serves as a viability test of the culture. Expansion of the package is an indicator of healthy (viable and vital) yeast. Although beneficial, cultures do not need to be activated prior to inoculation.


The Activator™ package contains a minimum 100 billion cells in a yeast slurry. The Activator™ is designed to directly inoculate 6 gallons (22 L) of must or juice with the same pitching rates used by professionals.

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. 
  2. To Activate, locate and move inner packet to a corner, place this area in palm of one hand and firmly smack package with the other hand to break the inner nutrient packet. Confirm the inner packet is broken.
  3. Shake the package well to release the nutrients.
  4. Allow package to incubate and swell for 3 hours or more at 70-75 °F (21-24 °C), this allows for yeast metabolism to begin prior to inoculation, the CO₂ produced causes the package to swell. If you do not require proof of activity, bring package to room temperature and proceed to the next step immediately and Direct Pitch.
  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 70-75 °F (21-24 °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.

Full swelling of Activator™ packages is not required for their use. The contents of Activator™ packages may be direct-pitched without prior activation. Our smack pack technology is intended to be a tool for your use in determining viability, and in initiating metabolism for faster starts to fermentation.

Sterile Packaged Product – UV Light Barrier – 100% Guaranteed Pure

Refrigerate between 34-40 °F (1-4 °C).

Do not freeze.

Best if Used by: This package is best when used within 6 months of the manufacturer’s 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.


Our Product Warranty states that we guarantee the viability of the yeast in our Activator™ packages for 6 months from the manufacture date 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 6 month guaranteed shelf life, some loss of viability is to be expected. This will vary from one strain to another. Activator™ packages that are 4 months old or older may require additional time to swell after activation. Activator™ packages will sometimes swell slightly, or moderately, during shipping or later while properly stored. This is not an indication of deterioration if the package is less than 6 months old and has been properly handled. This is result of trace amounts of nutrients, still available at the time packaging, causing 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.