Mash Out! December 2019

Each month, I will attempt to answer your questions here on the Canadian Homebrewers Association website. Please email me your questions at mike@canadahomebrews.ca

What is a yeast starter and why do we make them? How and when do we make a yeast starter?

Eric Formo

CHA member Eric Formo wrote in and asked about yeast starters. Here we go!

A yeast starter is basically a smaller batch of beer that is made prior to your actual brew day. The purpose of a yeast starter is to get your yeast ready for making beer by ensuring that your yeast are alive, that you have enough yeast cells and to get those little critters revved up and ready to go!

Typically, starters are only make for liquid yeasts. Dry yeasts tend to have more than the necessary number of yeast cells for a healthy fermentation (220-230 billion cells). For a standard strength ale (1.060 OG or below), 200 billion yeast cells will give you good results. Most homebrew liquid yeast pitches contain 100 billion cells, so we need to amp it up a bit. It is also important to make starters for yeast pitches that may have passed their expiry date or that you have harvested from previous batches.

You don’t really need a conical flask or a stir plate to get a yeast starter going.

To make a starter, you need some wort. It’s super easy to grab a can of Propper Starter canned wort from your local homebrew shop, or even using the final runnings off of a previous batch (providing that the runnings are 1.030-1.040 and you’ve saved it in a sanitary way), but making a starter using some dried malt extract (DME) is pretty simple too.

You will need: 

  • a half gallon pot with lid 
  • a liquid measuring cup 
  • a whisk 
  • half a cup of DME
  • ice
  • a vessel to prop up your starter (an erlenmeyer flask or a 1 gallon growler works)
  • a funnel
  • some tin foil
  • a thermometer 
  • scissors
  • sanitizer
  • a stove
  • a stir plate is optional and does provide better results but isn’t 100% necessary

In your half gallon pot, measure out 1100 ml of water. Put it on the stove and bring it to a boil. Add your DME and whisk vigorously. Be careful to watch for boil overs. Boiling wort will burn you and isn’t fun to clean up. Let the wort boil for 10 minutes. After that, sanitize your lid and put it on the pot. Then you’ll want to make an ice bath in your sink. Place your pot of wort in the ice bath and give it a swirl once in a while. You’ll want to cool the wort to the optimal temp for fermentation depending on your yeast strain. Check your yeast package or the yeast lab’s website for the correct temp.

While your wort is cooling, sanitize your funnel, the container that you’re using to prop up your starter, your scissors and the outside of the yeast package. Once the wort is cooled, pour it into your container. If you’re using a stir plate, you’ll want to sanitize your stir bar and add it to the wort. Then cut open your yeast package and carefully pour it into the container.

Sanitize a piece of aluminum foil that is large enough to cover the mouth of your container, then cover the mouth of the container just tight enough so that it doesn’t fall off. You want oxygen to be able to get in. If you’re using a stir plate, go ahead and put the container on the stir plate, line up the stir bar with the magnetic base and turn it on. If you are not using a stir plate, place one hand over the mouth of your container, hold the bottom with your other hand and shake the snot out of the container. Shake it until the whole container is filled with foam. Then place it in your fermentation chamber or somewhere close to your yeast pitching temperature.

Let the starter sit in the warm space or on the stir plate for around 24 hours. Some people will cold crash and decant the starter, others will just pitch the whole thing into their full batch of chilled wort—it’s up to you.

That is the basics of how you make a starter. It is definitely recommended and you really don’t need much to be able to do it. It will significantly improve your yeast health and fermentation. 

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