Yeast Starter

How-to: Making a Yeast Starter

You’ve finally decided to take your brewing to the next level, and you’re hoping that making a yeast starter might do that for you. Making a yeast starter is a great idea for getting the most out of your beer, and there are so many ways it can improve on your hard work and creativity. And best of all, hopefully you’ll realize that making a yeast starter is so easy and rewarding, you’ll want to do it for nearly every batch you brew.

In our post on planning a yeast starter you learned how to find your ideal pitch rate, calculate the number of yeast cells you need, and determine the size and number of steps needed to generate enough yeast from your existing smack pack or vial. In this post I’ll walk you step by step through making a yeast starter. So grab your calculations and let’s learn to make some yeast!

Making a Yeast Starter

Things you’ll need…

Items for making a yeast starter
Basic Yeast Starter items
  1. A smack pack or vial of liquid yeast (no dry yeast here)
  2. A glass jar (at least 1 qt), a growler, or an Erlenmeyer Flask (ideally 1L or 2L)
  3. A foam stopper or some tinfoil to cover your starter vessel
  4. Some DME – anything light-colored will do.
  5. Tap water
  6. A pot to boil in, potholders
  7. Ice water bath
  8. Sanitizing solution
Optional Items…
    1. Yeast Nutrient (helpful if you’re pitching older yeast)
    2. Stirplate – can improve the yield of your starter
    3. Refractometer to check the OG of your starter.
    4. Thermometer to check the temperature of your starter wort

Step 1.  Preparation

Yeast
Making a yeast starter
Wyeast 1056 for a starter

If you have a Wyeast smack pack, take it out of the refrigerator and smack it a few hours before you plan on making a yeast starter. While this isn’t required, it does prime the yeast with a small amount of nutrient-rich liquid to wake them up and get them going. Set this aside for later.

Equipment

Make a bowl of your favorite sanitizing solution. You’re going to want to sanitize the following items:

  • Foam stopper or tinfoil cover
  • Scissors (if you’re using a smack pack)
  • Yeast package
  • Starter vessel (growler, flask, jar)
  • Magnetic stir bar (if using a stir plate)

Sanitation is important when you are making a yeast starter because bacterial contamination in your starter can ruin your beer. If the yeast starter smells rancid or funny, don’t use it!

Wort Ingredients

Your starter wort will need water, dry malt extract (DME) and yeast nutrient (optional). In general, you want to target an original gravity in the range of 1.036 – 1.040 for your starter wort. A good ratio of DME to water in order to achieve that OG is about 1 gram of DME for 10mL of water. That means for a 1000mL starter, you would use 100 grams of DME(Tip: If you know the evaporation rate for your system you can add enough extra water so you hit your target starter volume after a 10-15 minute boil.)

It’s important to remember that when you are making a yeast starter, you are making a small batch of beer. However flavor, alcohol content, body, bitterness, mouthfeel, etc are not important. The purpose of the beer, when making a yeast starter, is to provide your yeast with an ideal environment to reproduce.

If you are using yeast nutrient, check the label on the package you are using to see how much. (I use Wyeast Nutrient Blend  with the recommended usage of ½ tsp per 5 gal of wort, or a pinch for a 1L starter.) Since our boil time is only 10-15 minutes you can add the nutrient just as the boil begins.

Step 2.  Make the starter wort

Add the water to your boiling pot and heat it on the stove. As the water is heating up add your DME and yeast nutrient. Make sure to mix thoroughly to prevent any DME clumps from forming (I like to use a whisk), and bring this mixture to a boil. As always, watch for boil overs. Even though this is a small batch of wort boil overs can and do happen.  You are going to be boiling this for about 10-15 minutes. There is no need to add hops here.

Step 3. Cool the starter wort

If you have an Erlenmeyer flask (or another vessel made of borosilicate, or Pyrex) you can transfer the wort directly into the vessel after boiling. Otherwise, you will need to keep the wort in the pot until it cools.

Take the pot or vessel containing the wort and place it in an ice bath to try and rapidly drop the temperature. If you have a thermometer now is a good time to put it in the wort (after you’ve sanitized it, of course) to monitor the temperature. Occasional gentle swirling to speed up the temperature drop is helpful.

Step 4. Pitch your yeast

Once the wort has cooled down to around 70ºF you can pitch your yeast. If you cooled the wort in your boiling pot, now is the time to transfer it to your starter vessel. Then either cut open your smack pack, or open your vial and pitch the yeast directly into the cooled wort contained in the starter vessel. If you are using a stir plate, now is a good time to add the (sanitized) magnetic stir bar.

Cover the starter vessel with either a sanitized square of tinfoil, or a sanitized foam stopper. In a pinch you can use an airlock as well, but something sanitized and breathable should be fine.

Step 5. Agitate your starter

Making a yeast starter even better: A stir plate
Yeast starter on the stir plate

Your starter will finish it’s job in about 24 hours, but you can make sure it does its best job if you agitate it during that time. If you own a stir plate, turn it on and sit back. If not, keep the starter at room temperature in a place where you will see it frequently, reminding you to periodically swirl it. Swirling, stirring, or agitating help expose the yeast to as much sugar in the wort as possible, and may aerate the starter as well.

Making a yeast starter
Active yeast starter

After 24 hours your yeast starter should be ready. If you’re not planning on using it right away, you can refrigerate it (covered) for up to a few days. It’s best not to let a starter go too long before pitching because your starter will not be an ideal environment for long-term hibernation. I’ve had success refrigerating for 3 or 4 days, but I wouldn’t go any longer.

Once you’re ready to use the starter you can either decant off the cleared wort above the yeast cake, or you can swirl it all up and pitch the whole thing.

This video depicts a yeast starter from pitching to high krausen in time lapse. This two minute video shows about two hours:

Notes on Settling & Decanting

After making a yeast starter, you can store it in the refrigerator to settle the yeast out. I find that if you refrigerate for 24 hours you get optimal settling. The gallery below shows a yeast starter when it was just put into the refrigerator, as well as at the 12 and 24 hour marks. Note how the initially cloudy starter becomes more dark and clear as time progresses.

Here’s a closeup view of the starter and the yeast cake at 12 and 24 hours:

If you decant the liquid portion at 12 hours, you are discarding less flocculent yeast and saving only highly flocculent yeast. If you’re decanting fluid to make a new starter you may be selecting out for highly flocculent yeast. If a specific flocculation is needed for your beer, you may be adversely affecting your fermentation and final product by decanting too early.


Last updated: June 2, 2014 at 7:03 am

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