Why You Should Be Making Yeast Starters, And How To Do It

Yeast starters are often mentioned by advanced home brewers as the one thing they wish they’d starting doing earlier. When I finally got round to trying I realised why.

Here I’ll show you how to start. It’s not as difficult as you may think.

make a yeast starter

As well as good sanitation and a decent recipe, one of the most effective ways of improving your beer is with a yeast starter.

Since I started honing my brew process, I now use yeast starters almost as a matter of course. I’ve noticed an improvement in my fermentations – they start quicker and stop later.

I used to have beers that finished fermenting after a day or two and never reached the final gravity I was after. This meant the beers were sweeter to taste and weaker in terms of alcohol.

I’m not a brewer who particularly monitors alcohol content, but it’s handy if the beer’s come out more or less as expected. Since I started making yeast starters this is the case more often.

Basically, if you’re not making yeast starters you’re missing a trick.

What Is A Yeast Starter?

The best way to think of yeast starter is as a small batch of home brew.

You make some wort and ferment it. The fermentation encourages your yeast to multiply and prepare themselves for the real batch of beer.

When you pitch those yeast into your actual wort they’re already in a healthy state to begin fermentation straight away.

Also, the pitching rate (number of yeast cells) will be such that the fermentation runs smoothly.

In short, when using a yeast starter your beer’s chances are greatly improved.

Why Bother With The Extra Effort?

You may be happy with your beer already and wonder why you need to even think about making yeast starters.

So here’s a bit more detail about how they improve the beer.

Reduce Infection

When you use yeast from a starter the yeast cells are already lively and in fermentation mode. As soon as they land in the wort they start fermenting.

The immediate start removes a period where the wort would otherwise be at risk, potentially vulnerable to airborne infections.

Once the wort is converted into beer it becomes more stable, so it’s best if this happens quickly.

Reduce Off-flavours

The fermentation process takes advantage of the natural reproductive cycle of yeast, which converts sugar into alcohol and gas.

A number of by-products are also created by the yeast, and these increase in number with each reproductive cycle.

Many of the by-products taste off and damage the flavour of your beer.

Using yeast starters reduces the number of cycles and limits production of off-flavours.

Increase Pitching Rate Without Buying More Yeast

Most yeast vials and smack packs come in quantities that are too small for a typical 5 gallon batch of beer.

Unless you want to buy several packs, a yeast starter is the only way to get the yeast up to recommended pitching levels.

How To Calculate Yeast Pitching Rate

It’s possible to calculate the yeast pitching rate fairly easily, especially if you use an online calculator such as Mr Malty.

You enter the type of yeast along the top, along with your batch size, beer type and starting gravity.

The calculator then tells you how many packs of yeast you need, or how much yeast starter to use to get the same pitching rate.

make a yeast starter calculator

Making Yeast Starters

Now you know what a yeast starter is and why you should start making them, I’ll show you how I make mine.

As always, I’m preparing the wort using the brew in a bag method.

You will need:

  • saucepan (2 litres/4 pints)
  • brew in a bag bag
  • thermometer
  • container for starter (a plastic bottle will do)
  • yeast
  • malt

Start with 200g/7oz of malt. I typically use pale ale.

making yeast starter malt

Heat 1 litre of water to 63°C/145 °F. After losses to boiling and the grain this makes 500ml/1 pint yeast starter.

making yeast starter temperature

Position your brew bag in the pot.

making yeast starter bag

Add the grain.

making yeast starter mash in

Cover and leave for an hour to mash. Check the temperature every now and then to make sure the temperature doesn’t drop more than 1-2°.

making yeast starter mashing

Remove the grain bag and let the wort drain into the pan. Boil for twenty minutes to sterilise.

making yeast starter boiling

Put the lid on and cool quickly. Running tap water is a pretty efficient way of doing this with these small quantities.

making yeast starter cooling wort

Sanitise your bottle. I use Star San which only needs twenty seconds to work and doesn’t need rinsing.

It really is essential that the bottle is sanitised, and that anything that touches the cold wort or yeast is too.

Any infection greatly increases the likelihood of spoiled yeast and wasted effort.

making yeast starter sanitising jar

When it reaches room temperature pour the wort into the sanitised bottle.

making yeast starter pouring wort

Now you’re ready to prepare the yeast.

You have several options:

I’m using washed yeast that I salvaged from the fermenter on bottling day.

The washed yeast comes from the fridge looking like this.

making yeast starter jar starter

The yeast is the light brown layer you can see on the bottom.

You could pitch the whole thing, but to avoid mixing flavours I usually discard the “beer” that’s at the top of the jar. It’s easy to pour off without losing the yeast if you have a steady hand.

After pouring the beer, you end up with a yeasty slurry like this:

making yeaster starter jar yeast

Pour that it into the wort that you already put in the bottle and swirl it around. A good fermentation needs oxygen so give it a good mix and shake.

making yeast starter

Cover the bottle. A loose piece of cling film will keep bacteria out but let gas produced during the fermentation escape.

making yeast starter closed

Leave the mixture to ferment.

making yeast starter fermenting

After a day or so krausen (a foamy head of yeast) builds up on top of the wort…

making yeast starter krausen

… and settles down again. The yeast then sinks to the bottom.

making a yeast starter : yeast have settled to bottom of bottle

The starter is now ready. This should be about 18 hours after high krausen.

You can keep for a couple of days in the fridge without damaging it. Any longer and you’ll need another starter to revive it.

As with the washed yeast the top layer of beer can be poured away to isolate the yeast.

On brew day, simply pour the yeast starter into the fermenter after you’ve cooled and aerated the wort.

making yeast starter pouring starter into fermenter

Ferment as normal.

A Few Questions

Should you throw the wort away or pitch it?

According to Palmer it’s best if the wort for the starter matches the final beer. This makes a lot of sense from a flavour point of view, but he also explains that it encourages healthy fermentation as well.

Yeast adapt to the wort they’re given and prepare themselves for that environment. If you throw them into a totally different wort you’re working against that natural process.

What if you don’t want to do a mini-mash?

Many brewers use dry malt extract to make a starter, which is an easy way to quickly prepare a wort.

Is it suitable for all beer types?

Yes, but it’s especially recommended for lagers and high gravity (strong) beers.

If you have any more questions, ask them below.

Happy brewing!

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  1. Tamás


    What do you think?
    I have washed yeast that previously fermented 15 l ale and I’ll make a starter. Will it be enough for 20 litres? :)

    • John

      Hi Tamás,

      I’d say that it will be more than enough, provided that it’s healthy and in good condition.