How to Make a Yeast Starter
Making a starter culture to increase the quantity of yeast pitched into a particular beer is a great way to assure consistent results. If you are brewing a high gravity beer (greater than 1.065 original gravity) or a lager that will be fermented cold then you need to increase your pitch rate by pitching more packages of yeast or making a starter culture.
The WYeast smack-pack is designed to inoculate 5 gallons of standard ale wort (O.G. < 1.060, 65-72°F). When brewing high gravity beer (O.G. >1.060) or cold fermented lagers or ales (<65°F) additional yeast will be required. An Activator contains approximately 100 billion cells which will deliver slightly less than 6 million cells per milliliter in a 5 gallon batch of beer.
The easiest and best way to insure yeast growth and health requires using a malt based media (DME) fortified with nutrients. Gravity should be kept near 1.040 and cultures should be grown at 70°F.
- 0.5 cup DME (100g, 3.5oz)
- ½ tsp Yeast Nutrient
- 1qt.(1L) H2O
- Mix DME, nutrient, and warm water.
- Boil 20 minutes to sterilize.
- Pour into a sanitized flask or jar with loose lid or foil.
- Cool to 70°F.
- Shake well and add yeast culture.
Timing of Starter:
Starter growth is usually maximized within 24-36 hours. The gravity of the starter should always be checked prior to inoculation into wort to assure proper cell growth . Cultures should be used immediately, or refrigerated for up to 1 week before using. Cell viability will decrease rapidly if culture are left at ambient temperatures for extended time.
Stirring and O2:
Agitation aids in removing inhibitive CO2 from suspension as well as possibly adding small amounts of oxygen. Stirring or shaking the starter periodically or using a stir plate will improve cell growth. The use of stir plates has been shown to increase cell growth 25-50% over a non-stirred starter.
Caution: It is important to understand that creating a starter can increase the risk of infection by undesirable organisms. Small levels of contamination can multiply to unacceptable levels, causing undesirable effects on the finished product. Use all of the same sanitation practices that you would while normally brewing.