In our quest for better beer, one of the small things you can do to turn out a better brew is to make yeast starters for every batch. The added benefit is that you don’t have to buy yeast as often.
The basic concept is that you take a small of wort, ususally made from dry malt extract, and add a small amount of yeast, which may not be so healthy. In 24 hours, you get a much larger amount of healthy yeast.
Whether you are starting with a new vial of liquid yeast, or taking it off the top of a fermenting beer, the process is the same. I choose to buy new vials of liquid yeast and make it last for as many generations as possible. I make a starter larger than I need (generally 1 quart for 5 gallons), and pour some off for future use. 8 ounces go in a mason jar in the fridge, the other 24 go into my freshly made wort. I have done this as many as 8 times before buying a new vial of yeast!
If you have brewing software, create a beer using light dry malt extract (DME) with a starting gravity of 1.040. To grow yeast, we don’t need a high sugar content. If you don’t have brewing software, you can use 4 ounces per quart. If you don’t have a scale, just use a cup per quart.
I then filled up the flask to the 600 mililiter mark and place it on the stove. I bring it to a boil and let it go for 5 minutes to sanitize everything. It’s a good idea to place a hop pellet in the wort, but I didn’t have any laying around this time.
As soon as it is done, I put it in a sink filled with water and cool it down. You don’t have to get it down to fermentation temps, body temp will be just fine. We are trying to grow yeast, not make beer. Within 24 hours, the yeast should have done it’s job and reproduced like crazy, but you can give it more time if you like. Here’s a picture of my DME starter and a 4th generation sample of California Ale Yeast.
I poured off 8 ounces into a mason jar, and dumped the rest into my beer. Just a few hours later, it was bubbling away.