How to propagate yeast (+3 things you need)

In this brief guide, we will answer the question ‘How to propagate yeast?’. Yeast can be cultured conveniently if you put aside a little amount and let it grow. Yeast can be grown without the store-bought pouch by using ingredients found in the kitchen.


  • potato
  • flour
  • sugar

How to propagate yeast?

To propagate yeast, we recommend dividing the yeast starter before we allow fermentation to occur. If we are sure to do that, we can obtain a clean and healthy sample for eight generations.

The industrial way

You will need the following tools and ingredients to propagate yeast at a large scale:

Kitchen scale

Yeast nutrients

canning jars 

Dry Malt Extract

Ferem cap S foam control 

Kitchen Scale 

Erlenmeyer Flask 


  1. Make sure your Erlenmeyer flask is sterile. If you have 3 to 3.5 liter of starter culture, you need a flask of a capacity of 5 liters.
  1. Weigh the Dry Malt Extract. You will need 100 grams per liter of starter. 
  1. Transfer the Dry Malt Extract into the Erlenmeyer Flask. Before you do make sure, the funnel and flask are completely dry. Any moisture that is left behind will cause the Dry Malt Extract to become sticky and cause havoc.
  1. Fill the required amount of warm water into the flask, be sure to rinse the Dry Malt Extract residues from the funnel.
  1. Use an aluminum flask to cover the mouth of the flask.
  1. Swirl the flask to let the Dry Malt Extract mix with the warm water. 
  1. When the water cools down, we put it on the stir plate. Place sanitized magnet beats inside the flask to allow the stirring to take place together with heating.
  1. If you do not have an Erlenmeyer flask, use the stovetop and a pot instead of an electric plate. Not every flask can withstand extreme temperatures, therefore choose accordingly.
  2. Now put two drops of Fermcap S Foam Control. Doing so will prevent the wort from boiling over and flooding the stovetop.
  3. Bring the wort to a boil, make sure that the foil allows some steam to pass through.
  4. Take the wort off the heat and let it chill as quickly as possible. 

To prepare the yeast that will inoculate:

  1. Make a starter of approximately 3 liters and leave it on the stir plate for twenty-four hours. A milky white appearance indicates that yeast cells are ready for fermentation.
  1. Divide the starter into three or four separate jars that are already sterile.
  2. Do not tighten the jar lid all the way through to allow some of the gas to escape.
  1. From the starter, isolate around 500 ml into a sterilized jar and store it in a refrigerator. This extra starter can build up to obtain harvested yeast 7 -8 times.

The following method is simpler, than the previous and makes use of utensils already found in the kitchen.

How to make Sourdough Yeast starter?

You need

  • Potatoes
  • Jar
  • saucepan
  1. You do not need a yeast starter but potatoes to cause yeast formation. 
  2. Put a peeled potato in freshwater in a covered saucepan.
  3. Boil it until it becomes soft.
  4. Mash it thoroughly.
  5. Put it back into the water it was cooked in. Mix it well to make a concoction, add a teaspoon of sugar and salt. Adding salt and sugar is optional and store it in a jar or bowl.
  6. Cover with a cheesecloth or porous cloth. Make sure that air can perforate but contaminants cannot.
  7. Let it sit for a few days to allow fermentation to occur.
  8. After 24 hours you will be able to see bubbles at the top meniscus of the jar. After 2-3 days, you will have sufficient quantity ready to use the yeast for fermentation. 
  9. You can keep adding water to allow the yeast culture to keep propagating. Just make sure it doesn’t deplete or get infested by pests. 

Other FAQs about Yeast which you may be interested in.

How much is a package of yeast?

How many teaspoons are in a packet of yeast?

How to make yeast from flour?

You need

  • Add 1 1/4 cups of all-purpose flour 
  • 1 cup pure warm water 
  • A sanitized jar 
  1. Mix flour and water and keep at room temperature for a few days. 
  2. As fermentation occurs you will see bubbles and froth. 
  3. After three or four days, the fermented yeast will be ready for use
  4. You can store the rest in the fridge.

The Crucial Steps to successfully propagate yeast

  • Do not put a lid on to allow the exchange of air to occur 
  • Remember to use pure and clean water. Chlorinated water will prevent the growth of yeast.
  • After the culture is sprouting and ready. Put it in the fridge to prevent it from spoilage.
  • Shake the Jar vigorously to level out the distribution of the yeast, the substrate (the food for yeast).

In this brief guide, we answered the question ‘How to propagate yeast?’. Yeast can be cultured conveniently if you put aside a small amount safely and wisely. We discussed two ways; large scale and at-home production.