A yeast starter is a nano-batch of beer brewed with the sole purpose of getting your yeast ready to cleanly ferment your main wort.
Starters provide the perfect environment for the yeast to replicate and build up, so you have a solid cell count to ferment your beer. You will have a shorter lag time and your wort will ferment more quickly and fully.
If done properly, a starter lowers your chances of infection from bacteria and wild yeast.
Making a starter also ensures your yeast is viable and active before pitching.
The end result – you’ll get much better homebrew!
Equipment needed for a yeast starter
Large glass bottle (two quarts/liters or more).
Steps to making a starter
Rehydrate your yeast if using dried yeast.
Clean and sanitize your bottle, funnel and thermometer.
Boil half a pound (100 g) of dry malt extract with
¼ tsp of yeast nutrient and 1.5 quarts (liters) of water for 10 minutes.
Seal and chill in an ice bath until you hit the top of the yeast’s working range.
Pour your chilled wort into your bottle.
Pour in your yeast and cap with sanitized aluminum foil.
Shake it until you get sick of it.
Move to somewhere warm enough to ferment.
Between 4 and 24 hours your yeast will hit krausen, which means it is actively fermenting and has developed a thick creamy head.
I typically make my starter the night before I brew.
This process will make starter a bit over one quart/liter, which is perfect for moderate strength ales.
Double this volume for lagers and strong ales.
Tips for Yeast starter success
Bottle a few quarts (liters) of wort from your fermenter in plastic bottles before you pitch your yeast.
You can freeze these and reuse as your starter wort.
Just make sure you dilute to 1.020, and then boil and cool to sanitize.
When you make your starter, also clean and sanitize your fermenter at the same time.
You can sit the starter in your sealed fermenter for a sanitized environment. Plus you now have one less job to do on brewday.
For an extra layer of paranoia, you can sit your fermenter in your scrupulously cleaned and sanitized fermenting fridge.
Shaken and stirred
Your yeast starter will work best if it’s oxygenated and the yeast is in suspension.
The simplest way to do this is seal the starter and shake the hell out of it. Repeat a couple of times a day.
You can also use a stir plate which keeps the yeast in constant suspension through a magnetic bar. They are fun to make and use but not essential.
You are making a healthy yeast population, not beer, so ferment on the warmer side of your yeast’s temperature range.
This will help the yeast replicate and prepare for the task of fermenting your main wort.
Pitch the lot or just the slurry?
As you may imagine, the starter’s fermented wort isn’t A-Grade homebrew. It was fermenting warm, over-oxidized and had an over-the-top pitching rate.
Will this impact your final beer quality? Possibly.
If you are making a large starter (over two quarts/liters) and a lighter flavored beer, it may.
In this case, let the yeast settle out (chilling will speed this up).
Pour off most of the starter wort and pitch the remaining slurry.
If your starter is less than two quarts (liters), you can safely pitch the lot with negligible impact on beer quality.
Pitch at full krausen or wait?
Yeast runs through a cycle of taking in resources, fermenting your wort, preparing for hibernation and sleeping.
In preparing to hibernate, yeast cells take in resources so they are supercharged for the next fermentation.
You may rightly ask whether you should let your yeast starter run through a full cycle of fermentation before pitching.
There are a few variables and it gets a bit sciencey.
Basically if your starter is made on only malt (ie no refined sugars) and similar strength and style to your main wort, you are better to pitch at high krausen.
Be warned, this space gets academic really quickly.
Far too many forum threads are taken up debating things with marginal impact on your beer quality.
As long as you pitch your starter somewhere between high krausen and three days, it’ll be fine.
Make a starter at all?
You may be thinking that starters sound like a fair bit of work. There must be another option...
Yes! Instead of making a starter, you can rehydrate and pitch two packs of dried yeast.
This will give you the benefits of making a starter in exchange for an extra five bucks on your homebrewing budget.
If you’re time poor and still trying to brew, this could work for you.
Want To Step Up Your Homebrewing Game?
Take your homebrewing to the next level with our advanced extract kit homebrewing guide.
We've packaged nearly 20 years of medal-winning homebrewing experience in this practical and results-focused guide.