Getting Off to a Good Start

Jump-Starting Fermentation With a Yeast Starter

The first time that you ever home brewed beer you probably spent a day or two after the brew nervously checking the fermentor for signs of activity. Any bubbles in the air lock yet? You had read that it could take a while for fermentation to start, but you did not think it would be this long. Finally, after a day and a half, you see signs of bubbles and you are relieved that something is happening.

It does not have to be like that, though. There is a way to promote faster, stronger, and more complete fermentation for beer. It is called a yeast starter.

Two Liter Yeast Starter

With Foam Stopper and Stir Plate

Yeast Starter

Gearing Up

The Equipment You Need for a Yeast Starter

If you would like to create a starter for your beer the only piece of equipment that is really necessary is a Pyrex Erlenmeyer flask with an airlock or foam stopper to seal it off. The entire yeast starter process can be performed in just this flask.

There are different sizes of Erlenmeyer flasks available for this process, usually in 1 liter, 2 liter, and 4 liter sizes. The size that you will need depends on several factors. These factors include the age of the yeast you are using (all brewing yeasts come with a "produced on" date), the starting specific gravity that is expected for the beer you are brewing, and the size of the batch of beer you are creating. 

For most batches of beer I have found a 2 liter flask to be ideal. Erlenmeyer flasks for yeast starters are available at just about every home brewing supply store. I always recommend visiting your local supply store for home brewing equipment and advice if there is one nearby. 

There are also optional pieces of equipment that you can use to improve the performance of your starter, including a stir plate or an air stone. More on these later.

Creating a Starter

Creating a yeast starter is actually quite simple - it is similar to creating a miniature batch of beer. You simply mix a light-colored dry malt extract into boiling water and let it boil for 10-15 minutes to sterilize the mixture. The proportions are usually half a cup of dry malt extract to two cups of water, although the totals of each are going to depend on the size of the yeast starter (which is determined by several factors, as discussed above).

This boil can take place directly in the Erlenmeyer flask, although there is a strong risk of a boil-over in the flask. Most brewers avoid a boil-over by either performing the boil in a pot and then transferring the mixture (now called "wort") into the flask, or by adding just a drop of a substance called "Fermcap-S," which prevents boil overs, to the wort in the flask at the start of the boil. Fermcap can also be found at your local home brewing store.

After boiling, the wort is cooled quickly to room temperature. The beautiful thing about Pyrex Erlenmeyer flasks is that they can be taken off of a hot stove and placed directly into an ice bath to cool without shattering. You do want to cool the wort quickly in an ice bath because it will form compounds with bad flavors if it sits warm too long.

After the wort is cooled the yeast is added and left to start fermenting the sugars present for 18-24 hours. This kick-starts the metabolism of the yeast and allows the yeast cells to multiply. If the real batch of beer that you are preparing to brew is very strong this yeast will be better equipped to handle it, rather than being shocked by the sugars. If the beer is not quite as strong the yeast starter is still effective because it will speed up the fermentation process.

When the yeast starter is ready it can be added directly into the real batch of wort that you are brewing.


Enhancing Yeast Starters

While simply creating a yeast starter will improve your beer, there are ways to enhance the yeast starter for an even better final product.

A great way to improve the results of the yeast starter is to swirl it. If you swirl the starter every couple hours it will keep the yeast in suspension in the wort, helping the yeast cells to keep working and multiplying. This process can be enhanced even further if you buy a stir plate, which constantly keeps the yeast in suspension. Note: this should only be done in the yeast starter, not during the fermentation of the actual beer.

Another option is to aerate the starter by shaking it regularly. Adding oxygen to the mixture promotes yeast growth. Again, you can take this up a step by using an air stone to constantly aerate the wort. It is important to note that introducing air while the yeast is working on wort produces diacetyl, which will give beer a bad flavor. If you aerate a yeast starter you will have to let it settle for about a day and then gently pour off most of the liquid in the flask before adding the yeast to the real batch of wort so that the off-flavor is not transferred.

Making a Yeast Starter

Using a Stir Plate