Use of fresh yeast and yeast starter

Although the quality of dried yeast has massively improved in recent years, fresh yeast is still far superior when it comes to selection. One must also remember that yeast is a living organism and that it is liquid in its natural form.

Dried yeast, on the other hand, is dehydrated. It should therefore be rehydrated before use. This has been tested and is somewhat debated, but essentially, we largely agree that dried yeast will benefit from rehydration. This is to get it started faster and ensure there is enough yeast.

Why make a yeast starter?

The advantage of dried yeast is that it is relatively inexpensive, has a long shelf life, and is easy to use. On the other hand, you often need to use several packets to ensure there is enough yeast.

With fresh yeast, it will often be necessary to make a yeast starter. This is to ensure you have enough yeast cells to achieve optimal fermentation. Fresh yeast must be stored cold, which causes the yeast to go dormant. Over time, more and more yeast cells will naturally die. If the yeast has been stored too warm, for example during transport, these can die even faster. This is why we make a yeast starter that both awakens the yeast from dormancy and ensures there is enough yeast for a trouble-free fermentation process.

If there is too little yeast, it can lead to off-flavors in your finished beer or fail to ferment down to the expected FG. In the worst case, some yeast types can stop the process entirely because they are not happy. Other benefits of a yeast starter are that you can make a larger starter than necessary and save some yeast for future use. Making a yeast starter will also be cheaper than buying several packets of fresh yeast, although that is also an option.

What do I need to make a yeast starter?

The principle of a yeast starter is simple. To get the yeast going, we essentially make a small wort so that the yeast gets nutrients and wakes up from dormancy. It then begins to multiply so that there is enough yeast. With a magnetic stirrer, we incorporate plenty of oxygen along the way and ensure the yeast stays in suspension.

Here is a simple list of the basic equipment you need. We also have this available as a starter kit for yeast starters with the following contents:

1. Magnetic stirrer: For homebrewers, a stirrer that can handle up to 5 liters will suffice.
   If you brew large quantities at a time, or make a lot of strong beer that requires a lot of yeast, it might be wise to invest in something larger.
2. Stir bar: The variant you use depends on how large a starter you are making. As a homebrewer with relatively small brews, the smallest stir bars, like 40x8mm, will usually suffice.
3. Erlenmeyer flask: The size of this will depend on how large a starter you need. If you primarily brew small batches, 2 to 3 liters will usually suffice. If you plan on larger or high-alcohol brews, or brew a lot with lager yeast, it might be wise to invest in a 5L flask right away. It's also worth considering that some air space is needed in the flask, as it can be difficult to get enough oxygen mixed in with a magnetic stirrer if it's too full. For example, if you are making 2 liters of yeast starter, a 2-liter flask will be too small.
4. Spraymalt (DME/Dry Malt Extract) to make wort: The color of this plays a minor role, as most of it will be discarded after the yeast has done its job. Choose the lightest type to be safe. It is also possible to use liquid malt extract, but the dry variant is easier to handle, weigh, and store if there's any left over.
5. Cotton stopper: This should be placed in the top of the Erlenmeyer flask. Cotton is a breathable material, which means it allows oxygen in, but still keeps flies, bacteria, wild yeast, and other unwanted organisms out of the flask.
6. Yeast nutrient: Yeast waking from dormancy needs sugar to multiply. To optimize the growth phase, it's beneficial to add yeast nutrient.
7. Antifoam: If you have a very full flask, or a particularly active yeast, it can quickly climb over the edge of the flask and onto your counter. If you boil the starter in the flask, antifoam also reduces the risk of boil-overs.

Procedure for making a yeast starter

1. Disinfect the cotton stopper beforehand. The simplest method for this is to wrap it in aluminum foil and place it in the oven at 150 degrees Celsius for about 15 minutes. If you boil the starter in a pot instead of directly in the flask, the flask must be disinfected with, for example, Star San.
2. Measure the correct amount of water, either in a pot or directly in the Erlenmeyer flask where you will make the starter. Then bring it to a boil. Feel free to add the stir bar, and the boiling process will disinfect it at the same time.
3. When the water boils, add the correct amount of spraymalt and yeast nutrient. As a rule of thumb, we use 100g of spraymalt per liter of water. This gives a starter with an OG of approximately 1.040, which is perfect for getting the yeast started.
4. Stir well to avoid lumps or burning at the bottom. Let this boil for 5-10 minutes.
5. After boiling, the starter must be cooled to below 25 degrees Celsius. This can be done in a water bath or ice bath.
6. Disinfect the yeast packet with Star San or similar. The same applies to scissors or a knife you use to open the packet.
7. When the starter has reached a low enough temperature, you can pitch the yeast.
8. Put on the disinfected cotton stopper and place the flask on the magnetic stirrer. It doesn't need to be high speed, but enough so that you see "dimples" on the surface of the starter.
9. Leave at room temperature with the magnetic stirrer running. How long it should run varies depending on the yeast type: how old the yeast is and how large the yeast starter is. This takes at least 12 hours, but often longer if the yeast is old. Most healthy yeast starters will be finished when the starter has turned milky white, and you can see the yeast flocculate (settle at the bottom of the flask) if you stop the magnetic stirrer for a few minutes.
10. Place the flask in the refrigerator. It should stay there for at least 24 hours before use, so the yeast can separate from the rest of the liquid and settle at the bottom of the flask.
11. Once the yeast has separated, you can pour out the liquid from the flask. Avoid shaking the flask and pour very carefully. The liquid will be heavily oxidized beer that adds nothing to your beer. Therefore, you want to get rid of this, but keep the yeast. When what you are pouring out starts to become cloudy: Stop. Depending on how much starter you have made, a few deciliters of liquid should remain in the flask in addition to the yeast. This is now your finished, built-up, and healthy yeast, ready to be added to your next brew. Feel free to taste the liquid you pour out. This will give you an idea of what flavors the yeast will add to your next brew, and you will also know if any infections or anything else you don't want in your beer have occurred.
12. It can be beneficial to take the flask with the finished yeast out of the refrigerator and let it slowly warm to room temperature before use. This is to allow the yeast to "wake up" before it does its job, and to avoid too large a temperature difference from the refrigerator to your wort.

If you want to skip the wort boiling process for the yeast starter, there is a ready-made solution for this. Propper Starter is pre-boiled starter liquid that only needs to be mixed with water. This can be a good alternative if you don't brew large quantities or particularly often. Cost-wise, a homemade yeast starter is a better alternative.

Quick / simplified yeast starter (Viability starter)

Sometimes you don't have time to make a yeast starter, or you simply forget about the whole thing until it's too late. There are also many who simply don't trust a starter that has to sit in the refrigerator before decanting. Cooling before decanting means that the cells go dormant again. Then it's difficult to know how much living yeast you have at pitching, even if the yeast is tempered before being added. Fortunately, there is a quick method that can solve this for you.

In short: You make a yeast starter in the same way as described above, but instead of letting it ferment completely, the entire starter is added at the right time.

Detailed explanation: Dormant yeast needs time to get going, i.e., a "lag phase." It is this lag phase we want to shorten with a yeast starter. With a regular yeast starter, we get the yeast going and let it do the job of consuming all the sugar in the wort. With the quick method, this process will not be fully completed. The principle here is that the yeast is added when it is most active. This means 6-8 hours after the yeast starter has been started. In other words, you will be able to make the yeast starter and have it ready for use as soon as brew day is over.

This will not be an optimal replacement for a classic yeast starter where we build up and increase the number of yeast cells, as the yeast may not have multiplied enough. However, this will still be a better solution than adding too little yeast that is also dormant, as the yeast added is already at its most active and will start working on your wort as soon as it is added. You also don't need to oxygenate the wort with this method, as the starter is full of oxygen when you pitch.

• The procedure is almost identical. You need about 1 liter of starter to get the yeast going.
• The starter should have an OG a few points higher than what you expect in the wort after brewing.
• Assume that 100g of spraymalt in 1 liter of water gives an OG of approx. 1.040.
• After 6-8 hours, you can add the entire starter to your finished wort, liquid included.
• Since the OG of the starter and the wort are roughly similar, it will not dilute the wort. Nevertheless, it is worth considering that this method increases the final amount of beer in the fermenter.
• With this, the color of the spraymalt can also play a role, especially if you brew small quantities. Therefore, avoid dark spraymalt if you are brewing a light beer.

Yeast storage

If you need to make more starters, don't have time to brew, or make a larger starter than necessary, you can save some of the yeast for future use. For this, we recommend a disinfected borosilicate flask. This can be placed in the refrigerator for future needs. Be aware that the yeast can continue to work here, so unscrew the lid occasionally to ensure that too much pressure does not build up in the flask. If the yeast is used within a short period, it can be used directly from the flask. If it has been stored for a longer time, it is advantageous to make a new starter with it.

How large a starter do I need to make?

It is difficult to give a definitive answer to this, as the amount of yeast you need depends on several factors.

• How old is the yeast?
• How has the yeast been stored?

Fresh yeast will die over time, so the older the packet of yeast is, the fewer live cells you have left that can multiply. If the yeast packet has been stored warm, the yeast cells can die even faster.

• How much beer are you brewing?
• How strong will the beer be?

The more beer you brew, the more yeast you need. The same applies to the strength of the beer, as wort with a higher OG needs more live yeast cells to carry out a healthy fermentation process.

• Which yeast type are you using?

There is a big difference between ale and lager yeast. Lager yeast usually needs almost twice as many yeast cells as ale to ferment cleanly.

We recommend a calculator

The best method to find out how large a yeast starter you need is to use a calculator specifically designed for this. You can find this, for example, on White Labs' pages or in Brewers Friend. Most recipe building programs also have a variant of this calculator built-in.

We can also recommend the Brewfather app, where you will be able to calculate this by stating how old the yeast is. The app will then base its calculations on your recipe and determine exactly how large a starter you need.