How to Make a Yeast Starter for Beer at Home

Brewing beer at home is a rewarding hobby that combines science, art, and a bit of alchemy. One crucial step in ensuring a successful brew is making a yeast starter. In this blog post, we'll dive into what yeast starters are, why they are important, and how to make one at home, covering the equipment, ingredients, and best practices. Additionally, we'll explore what's happening at the microscopic level during this process.

What is a Yeast Starter?

A yeast starter is a small batch of wort (unfermented beer) that is used to grow and propagate yeast cells before they are pitched into the main batch of beer. It acts as a sort of yeast incubator, allowing the yeast to multiply and become active before being introduced to the larger volume of wort.

To keep things simple, there are two types of starters home brewers utilize.

1. Viability Starter - a viability starter is only intended to waken the yeast and get it ready to chew on your wort's sugars.  Brewers can utilize the same volumes and practices for each batch of beer.  Starters used for viability purposed are to return the yeasts cell count to its original value or better. If you are concerned about yeast pitch rates, you will want to use method two, Pitch-rate Starters.

2. Pitch-rate Starter  -  While the process of making any yeast starter is identical, a pitch-rate starter is intended to grow your yeast colony to a specific cell count to match the beer you will be brewing.  You will need to reference a yeast calculator to determine the appropriate size starter based on your yeast's current viability, the volume of your beer you will be fermenting and the original gravity (OG) of the wort. 

Why is a Yeast Starter Important?

1. Ensures Healthy Fermentation: By increasing the yeast cell count, you ensure that there are enough healthy, active yeast cells to ferment your beer efficiently. This helps to avoid off-flavors and incomplete fermentation.
2. Reduces Lag Time: A yeast starter reduces the lag time between pitching the yeast and the start of active fermentation. This helps to prevent unwanted bacteria and wild yeast from taking hold.
3. Improves Consistency: Using a yeast starter can lead to more consistent results in your brewing, as it provides a more controlled and predictable fermentation process.

What Happens at a Microscopic Level?

Yeast cells are living organisms that convert sugars into alcohol and carbon dioxide through the process of fermentation. In a yeast starter, you are essentially providing the yeast with an ideal environment to multiply. When yeast cells are pitched into a starter wort, they consume the sugars and nutrients, reproduce by budding, and increase their population. This propagation ensures that a sufficient number of yeast cells are available to efficiently ferment the main batch of beer.

Equipment Needed

• Flask or Large Jar: A 2000 ml (2 liter) Erlenmeyer flask is ideal, but larger or smaller sized flasks can be used depending on the number of yeast cells you wish to grow.
• Stir Plate and Stir Bar: Optional but highly recommended for continuous agitation, which helps oxygenate the wort and promotes yeast growth. Using a stipulate will significantly increase the volume of yeast cells you are able to propagate.
• Airlock: To allow gas to escape while preventing contaminants from entering. Three piece airlocks can be used in conjunction with stoppers. For simplicity sake, we tend to used sanitized aluminum foil for our own starters.
• Brewery Cleaner: We prefer PBW from Five Star Chemicals, this cleaner will remove even the toughest of organic contaminates.
• Sanitizer: To ensure all equipment is free of bacteria and wild yeast. We recommend the industry standard, Star San from Five Star Chemicals.
• Measuring Cup & Scale: If using a flask, your unit of measures will be printed on the flask. However, we find that a small kitchen scale is ideal for weighing out the dry malt extract.
• Thermometer: To monitor the temperature of the wort, an adhesive thermometer works great for this as it is permanent.

Ingredients

• Dry Malt Extract (DME): About 100 grams of Pilsner DME per liter of water.
• Water: Filtered or distilled water is best.
• Yeast Nutrient: Optional but can enhance yeast growth. We prefer the yeast nutrient from Wyeast.
• Yeast: The specific strain you intend to use for your beer.

Best Practices

1. Clean & Sanitize Everything: Thoroughly clean & sanitize all equipment that will come into contact with the starter wort to prevent contamination. Follow the recommended directions as outlined by the manufacture of the cleaning products.
2. Boil the Wort: Boil the water and DME for about 10-15 minutes to sterilize the mixture. If you wish to eliminate this step, Omega Yeast makes a prepared medium by the name of Propper. Simply empty the contents of the 16 oz. can into your flask and add 16 oz of sterile water. This eliminates the need for boiling and cooling the wort, saving time for more important tasks.
3. Cool the Wort: Quickly cool the wort to around 70°F (21°C) to create an ideal environment for the yeast. The fastest method is to submerge your flask into a bath of ice water, gently swirling the hot wort to improve surface contact with the ice bath. 
4. Aerate the Wort: Pour the cooled wort into your flask or jar and shake it vigorously to introduce oxygen, or use a stir plate for continuous aeration.
5. Pitch the Yeast: Add your yeast to the aerated wort. Always remember to sanitize your yeast package prior to opening it. If scissors will be used, ensure they are also cleaned and sanitized.
6. Cover and Ferment: Place an airlock on the flask or cover loosely with sanitized foil, and let it ferment at room temperature for 24-48 hours.

Step-by-Step Process

1. Measure and Boil: The volume of your starter (water and extract) will vary depending on your needs. The rule of thumb is 1 gram of DME per 10 ml of water. For a 1 liter starter, measure 1 liter of water and add 100 grams of DME. Boil for 10-15 minutes to create your starter wort.
2. Cool Down: Quickly cool the wort to <70°F (21°C) by placing the pot in an ice bath.
3. Sanitize and Transfer: Sanitize your flask or jar, and transfer the cooled wort into it. If you perform your boil in the flask, this step is eliminated (our personal preference).
4. Aerate Shake the flask or jar vigorously, or place it on a stir plate with a stir bar. Utilizing an inexpensive stir plate is ideal.
5. Add Yeast: Pitch the yeast into the wort.
6. Ferment: Cover with a sanitized airlock or foil and let it ferment for 24-48 hours. Keep your starter covered with a towel to prevent light from causing off flavors.

After 24-48 hours, your yeast starter should be ready. You’ll notice a layer of creamy yeast at the bottom of your flask or jar. This is your active yeast, ready to be pitched into your main batch of beer. We like to decant off the excess liquid which is spent wort, preventing it from making its way into the beer. This is not required, but helps.

Creating a yeast starter is a small investment of time that can significantly improve the quality of your homebrew. By ensuring a healthy population of yeast cells, you promote a clean, efficient fermentation process that results in better-tasting beer. With the right equipment, ingredients, and practices, making a yeast starter at home is a straightforward process that can enhance your brewing experience.

Happy brewing!