Whether you prefer to work with liquid yeast that is packaged in vials or in foil pouches, the amount of yeast contained within them may not be the proper volume for pitching into a 5-gallon batch –it depends on the original gravity of your beer. Whenever you brew a higher gravity beer you should propagate the yeast upward by feeding the yeast more sugar and nutrient in a separate container (to propagate simply means to increase by natural reproduction). This is called making a yeast starter.
By feeding your yeast more fermentable sugar in liquid form, you are encouraging it to eat heartily and multiply. Eventually, over the span of a few days, you will have the proper volume of yeast to pitch into a 5-gallon batch of beer. Remember- these procedures are recommended for liquid cultures only, not freeze-dried yeast.
Beer Gravity
High-gravity worts -those with gravities of 1.056 or higher- have a greater need for more yeast. For every gravity increase of 0.008 above 1.048, you should double the yeast volume. For more information on how to ascertain the gravity of your homebrew click here.
Propagating Vessels
Propagating can take place in any glass vessel that can be sealed with a rubber stopper, such as a mason jar, an old wine carafe, or an expensive pyrex flask. The bottom line is that the propagating container must be thoroughly sanitized and sealable with an airlock, just as with any other fermentation vessel.
You can create the perfect, sterile holding tank with a large 22-ounce or quart-size beer bottle. The small rubber stopper that fits the hole in the primary fermenter lid should also fit the bottle’s opening.
Here’s how to put your “sterile holding tank” to good use:
- Sanitize your bottle as you would any other piece of homebrewing equipment, along with a rubber stopper and an airlock. For more information on sanitizing equipment click here.
- Boil two cups of water with a half-cup of (pale) dry malt extract mixed in.
- When the extract and water mixture has cooled, pour the wort into the bottle, add the yeast culture, and give a good shake to introduce some oxygen into the wort.
- Seal the bottle with the stopper and airlock.
Lager yeast tends to reproduce slower than Ale yeast, even at proper temperatures. Therefore, higher pitching rates are needed in order to achieve the same concentration of yeast cells in the fermenting beer. The general rule is to pitch double the amount of lager yeast, or 2 cups of yeast slurry per 5-gallon batch.
You need to maintain a fairly high temperature (70° F) for the first 24 hours of the incubation period to encourage rapid yeast growth. The best time to pitch the yeast into your wort is while there is visible, active fermentation taking place; definitely pitch the yeast before it sediments out of suspension. For batches of beer larger than 5 gallons or for batches of beer with gravities greater than 1.056, you can easily increase the yeast volume by propagating your culture a second or third time, using the same procedures outlined above.
Remember that every time the yeast is transferred to a new vessel, there is an increased risk of contamination. Always practice immaculate sanitation when it comes to yeast handling.
Yeast Energizers and Nutrients
Just like the pills that are gulped by vitamin-deficient humans, energizers and nutrients have been developed for beer yeast. These vitamins and minerals are dietary supplements for yeast, designed to accelerate cell growth.
These products, which are easily obtained through your regular homebrew supplier, are fairly inexpensive but not always needed. You only need to use energizers and nutrients for high gravity worts (those over 1.056), or fermentable beverages with less than 60 percent malt content, such as Cider or Mead (most of the essential nutrients needed for yeast nutrition is contained in malt and to a lesser degree in your brewing water).
