Comprehensive Guide to Yeast Storage and Starter Culture for Homebrewing

[rafadtrisch]

Working with yeast in a microbiology laboratory, I’ve learned two fundamental lessons (as a principle, but especially over time): the importance of microorganism storage and how proper storage is crucial for doing good work. In beer production, yeast propagation affects fermentation, which, in turn, is directly related to yeast storage and handling. Maintaining stable and pure yeast cultures helps in producing consistently high-quality beer and is highly valuable for successful brewing. Good storage for beer production, whether on a large or small scale, needs to ensure that yeast can be stored for long periods in the simplest and most accessible way possible, keeping them genetically and phenotypically stable, and ensuring cell viability. In the laboratory, some techniques like solid media culture, liquid culture, lyophilization, and liquid nitrogen storage are commonly used. Each of these techniques has its advantages and disadvantages, so you need to evaluate your priorities when choosing how to store your yeast. It is, of course, always possible to buy ready-made stocks. But what if you, producing your beer at home, want to maintain a stock of yeast for your production? Is it possible? How can it be done without the materials of a microbiology laboratory and trained personnel?

If you buy ready-made yeast cultures, you may have heard the term “starter culture.” By following the necessary procedures, this technique allows for a clean propagation of yeast and is widely used by homebrewers to optimize fermentation. This way, you can ensure a higher number of viable cells for your fermentation. Thus, if you buy yeast (that is not dry!), you start with an X number of cells (usually 100 billion per pack, depending on the brand), which is not always enough for your preparation. The number of cells depends on the desired wort gravity, the final volume desired, the viability of the cells you have, and all this affects the number of yeast packs you generally use. Therefore, a starter culture is a great way to save and can be made at home.

To begin, you need to calculate the number of cells required for your preparation. Many books can help with this calculation, but online tools like the Yeast Pitch Rate and Starter Calculator (https://www.brewersfriend.com/yeast-pitch-rate-and-starter-calculator/) provide the necessary cell count based on OG and volume entered, calculate cell viability based on manufacturing date, and give the necessary data for making the starter properly.

With the results of the calculations in hand, you can start making the starter!

Making a starter culture is similar to making a mini-batch and can be done with materials you have at home.

Materials needed:

• Erlenmeyer Flask or Glass Jar: A glass jar or Erlenmeyer (usually 1 to 2 liters) is ideal for preparing and fermenting the starter. It should be large enough to allow wort expansion and prevent spillage during fermentation. If you don’t have an Erlenmeyer, you can prepare the wort in a clean container that can be heated. Additionally, it should be large enough and able to be covered.
• Starter Wort: The wort can be made at home using dry malt extract (DME) dissolved in water. According to the book “Yeast: The Practical Guide to Beer Fermentation,” the typical ratio is 10:1. The previously mentioned calculator provides the exact volume to use.
• Yeast Nutrient: To support yeast growth, you need to add a yeast nutrient, easily found on specialized websites. The book “Yeast: The Practical Guide to Beer Fermentation” suggests ⅛ teaspoon, but some websites recommend ½ teaspoon. This amount is variable, depending on the volume to be produced.
• Heat Source (Stove or Microwave)
• Kitchen Thermometer
• Lid or Aluminum Foil: Used to cover the jar during fermentation, allowing gas exchange while preventing contaminants.
• Magnetic Stirrer (optional): Can be found online for reasonable prices, or you can make your own stir plate following some tutorials (example available at: https://www.homebrewersassociation.org/how-to-brew/homebrew-diy-making-a-stir-plate/).
• 70% Alcohol
• Liquid or Solid Yeast: Can be store-bought liquid yeast or yeast recycled from a previous fermentation.
• Sterilized Spoon or Spatula
• Scale
• Water

How to make the starter culture:

1. Weigh the DME and place it in the chosen container. Pressure cookers can be used for sterile wort, but Erlenmeyers are preferred as they can be placed directly on the stove.
2. Add water and yeast nutrient. The container should be large enough for the desired wort volume and have extra space to prevent spills. The entire procedure should be conducted in a sanitized and as sterile an environment as possible, preferably closed and dust-free. The pot should be closed once the ingredients are added and only opened when necessary.
3. Boil the mixture for 15 minutes, then turn off the heat. After cooling, if the mixture was made in a pot, transfer it to a new container. If it was made in an Erlenmeyer, yeast can be added directly. The starter temperature should be maintained between 18 and 24°C. Cover the container with aluminum foil or a cloth stopper, allowing for aeration. The starter culture temperature should be maintained between 18 and 24°C.
4. At this step, oxygen is important for proper cell growth, so agitation is recommended. You can use a shaker (typically found in labs, though you probably don’t have one), a magnetic stirrer (which can be homemade or found at reasonable prices), or manual shaking. The yeast should be incubated for about 24-36 hours, under continuous or periodic agitation, and your starter culture will be ready!

But what about yeast storage, as mentioned earlier? In the lab where I work, a commonly used technique is the Castellani method (storing a piece of culture medium with water in a sealed glass tube). This type of storage lasts about six months. With the help of some materials you have at home and some laboratory items that are affordable and easily found online, you can maintain this type of stock for your yeast.

Required materials:

• Glass flasks that can be heated and sterilized
• Pressure cooker
• Support material for the flasks in the pressure cooker
• Distilled water
• Petri dishes with yeast or slants
• Inoculating loops (disposable or reusable)
• Lamp
• 70% alcohol
• Agar
• Yeast medium for inoculation or previously made culture plates
• Erlenmeyers
• Parafilm
• Wort

To perform this technique:

1. To make the solid culture medium, mix 1.5% agar (found online or in Asian grocery stores) with wort. Heat the mixture in a pot, stirring until the agar is completely dissolved. The amount of medium to prepare depends on the number of plates or slants desired. After mixing, the medium must be sterilized. Place the mixture in a partially open flask or directly into small glass flasks (also partially open and positioned on a non-melting support) and sterilize in a pressure cooker for 15 minutes at maximum pressure. After sterilization, if making slants, tilt the flasks to the desired angle and close them until the medium solidifies. To make Petri dishes, handle them carefully. If using sterile plastic plates, keep them closed until ready for use. In a space with surfaces cleaned with 70% alcohol, place the closed plates near a lit lamp to help maintain sterility. Open the flask with the medium, flame the rim, and pour the medium into the plate, closing it as quickly as possible. Let the medium solidify with the plate closed. In both cases, plate or slant, inoculate the medium with a sterile loop. If the loop is reusable, heat it in the flame until glowing and let it cool before contacting the yeast. Incubate the plates or flasks at around 28°C until the colonies reach the desired growth levels. Without a laminar flow hood, contamination can be tricky to avoid, so monitor the colonies closely.
2. With the plates ready, the second step is to sterilize the distilled water. The procedure is similar to that used for the medium flasks. In smaller flasks (between 10 and 15 mL), fill one-third with distilled water and leave the cap partially open. Using a support, place them in the pressure cooker and maintain maximum pressure for 15 minutes. Turn off the cooker, close the flasks, and let them cool. Following the same recommendations as before, with the lamp on, cut a piece of agar from the plate or slant with a sterile loop and place it in the flask with sterile water. Don’t forget to flame the flask rim. After closing the flask, seal the cap with parafilm and shake it. It can be stored for six months in a dry, light-protected place.

The other storage method described below ensures greater cell viability and longer stock duration. In this method, the yeast is slowly frozen using a cryoprotectant (glycerin), without liquid nitrogen, and kept in the freezer.

You will need:

• Glycerin
• Water
• Pressure cooker
• Flask with a cap that can be heated and placed in the pressure cooker
• Plastic tubes
• 70% alcohol
• Isopropyl alcohol
• Starter culture

To prepare the stock:

1. Prepare a starter culture and keep it reserved while performing the rest of the procedures. Clean surfaces with alcohol.
2. In a flask, make a 50/50 mixture of water and glycerin. Homogenize well and place it partially open in the pressure cooker at maximum pressure for 15 minutes. Turn off the cooker, close the flask, and let it cool.
3. Light the lamp and handle the plastic tubes near the flame. Fill half of each tube with 50% glycerin and transfer the liquid from the starter culture, leaving only the decanted yeast, filling the rest of the tube with this yeast. The final concentration of the cryoprotectant, which prevents ice crystal formation and cell rupture, should be 25%.
4. Place the tubes in a container filled with isopropyl alcohol and leave them in the freezer for 24 hours. This should ensure slower freezing, reducing cell viability issues. Afterward, you can remove the alcohol and store the tubes directly in the freezer.

I hope this brief text helps you with the storage and handling of yeast for your homebrewed beer production.

 

[stamandster]

Very thorough thanks!

 

[beren]

Is this ai generated?

 

[day_trippr]

A popular "AI detector" applied to the first 3 paragraphs claims 12% of that was AI generated.
That level suggests "AI assisted" vs a complete AI work, but either could in fact be true.
fwiw, I believe it first appeared in the Brazil forum in their Brazilian-dialect Portuguese...

Cheers!

 

[beren]

Ah. Just very confusing to see a massive wall of text with no other post history.

 

[MaxStout]

OP doesn't appear to be promoting something. At least I don't see links shilling some site, so the post could be their earnest effort to contribute.

While I wouldn't call the guide "comprehensive," it looks like a fairly decent primer on the topic. Sort of akin to some of the articles members used to submit to HBT in past years.

 

[Perthbrewer]

Working with yeast in a microbiology laboratory, I’ve learned two fundamental lessons (as a principle, but especially over time): the importance of microorganism storage and how proper storage is crucial for doing good work. In beer production, yeast propagation affects fermentation, which, in turn, is directly related to yeast storage and handling. Maintaining stable and pure yeast cultures helps in producing consistently high-quality beer and is highly valuable for successful brewing. Good storage for beer production, whether on a large or small scale, needs to ensure that yeast can be stored for long periods in the simplest and most accessible way possible, keeping them genetically and phenotypically stable, and ensuring cell viability. In the laboratory, some techniques like solid media culture, liquid culture, lyophilization, and liquid nitrogen storage are commonly used. Each of these techniques has its advantages and disadvantages, so you need to evaluate your priorities when choosing how to store your yeast. It is, of course, always possible to buy ready-made stocks. But what if you, producing your beer at home, want to maintain a stock of yeast for your production? Is it possible? How can it be done without the materials of a microbiology laboratory and trained personnel?

If you buy ready-made yeast cultures, you may have heard the term “starter culture.” By following the necessary procedures, this technique allows for a clean propagation of yeast and is widely used by homebrewers to optimize fermentation. This way, you can ensure a higher number of viable cells for your fermentation. Thus, if you buy yeast (that is not dry!), you start with an X number of cells (usually 100 billion per pack, depending on the brand), which is not always enough for your preparation. The number of cells depends on the desired wort gravity, the final volume desired, the viability of the cells you have, and all this affects the number of yeast packs you generally use. Therefore, a starter culture is a great way to save and can be made at home.

To begin, you need to calculate the number of cells required for your preparation. Many books can help with this calculation, but online tools like the Yeast Pitch Rate and Starter Calculator (https://www.brewersfriend.com/yeast-pitch-rate-and-starter-calculator/) provide the necessary cell count based on OG and volume entered, calculate cell viability based on manufacturing date, and give the necessary data for making the starter properly.

With the results of the calculations in hand, you can start making the starter!

Making a starter culture is similar to making a mini-batch and can be done with materials you have at home.

Materials needed:

• Erlenmeyer Flask or Glass Jar: A glass jar or Erlenmeyer (usually 1 to 2 liters) is ideal for preparing and fermenting the starter. It should be large enough to allow wort expansion and prevent spillage during fermentation. If you don’t have an Erlenmeyer, you can prepare the wort in a clean container that can be heated. Additionally, it should be large enough and able to be covered.
• Starter Wort: The wort can be made at home using dry malt extract (DME) dissolved in water. According to the book “Yeast: The Practical Guide to Beer Fermentation,” the typical ratio is 10:1. The previously mentioned calculator provides the exact volume to use.
• Yeast Nutrient: To support yeast growth, you need to add a yeast nutrient, easily found on specialized websites. The book “Yeast: The Practical Guide to Beer Fermentation” suggests ⅛ teaspoon, but some websites recommend ½ teaspoon. This amount is variable, depending on the volume to be produced.
• Heat Source (Stove or Microwave)
• Kitchen Thermometer
• Lid or Aluminum Foil: Used to cover the jar during fermentation, allowing gas exchange while preventing contaminants.
• Magnetic Stirrer (optional): Can be found online for reasonable prices, or you can make your own stir plate following some tutorials (example available at: https://www.homebrewersassociation.org/how-to-brew/homebrew-diy-making-a-stir-plate/).
• 70% Alcohol
• Liquid or Solid Yeast: Can be store-bought liquid yeast or yeast recycled from a previous fermentation.
• Sterilized Spoon or Spatula
• Scale
• Water

How to make the starter culture:

1. Weigh the DME and place it in the chosen container. Pressure cookers can be used for sterile wort, but Erlenmeyers are preferred as they can be placed directly on the stove.
2. Add water and yeast nutrient. The container should be large enough for the desired wort volume and have extra space to prevent spills. The entire procedure should be conducted in a sanitized and as sterile an environment as possible, preferably closed and dust-free. The pot should be closed once the ingredients are added and only opened when necessary.
3. Boil the mixture for 15 minutes, then turn off the heat. After cooling, if the mixture was made in a pot, transfer it to a new container. If it was made in an Erlenmeyer, yeast can be added directly. The starter temperature should be maintained between 18 and 24°C. Cover the container with aluminum foil or a cloth stopper, allowing for aeration. The starter culture temperature should be maintained between 18 and 24°C.
4. At this step, oxygen is important for proper cell growth, so agitation is recommended. You can use a shaker (typically found in labs, though you probably don’t have one), a magnetic stirrer (which can be homemade or found at reasonable prices), or manual shaking. The yeast should be incubated for about 24-36 hours, under continuous or periodic agitation, and your starter culture will be ready!

But what about yeast storage, as mentioned earlier? In the lab where I work, a commonly used technique is the Castellani method (storing a piece of culture medium with water in a sealed glass tube). This type of storage lasts about six months. With the help of some materials you have at home and some laboratory items that are affordable and easily found online, you can maintain this type of stock for your yeast.

Required materials:

• Glass flasks that can be heated and sterilized
• Pressure cooker
• Support material for the flasks in the pressure cooker
• Distilled water
• Petri dishes with yeast or slants
• Inoculating loops (disposable or reusable)
• Lamp
• 70% alcohol
• Agar
• Yeast medium for inoculation or previously made culture plates
• Erlenmeyers
• Parafilm
• Wort

To perform this technique:

1. To make the solid culture medium, mix 1.5% agar (found online or in Asian grocery stores) with wort. Heat the mixture in a pot, stirring until the agar is completely dissolved. The amount of medium to prepare depends on the number of plates or slants desired. After mixing, the medium must be sterilized. Place the mixture in a partially open flask or directly into small glass flasks (also partially open and positioned on a non-melting support) and sterilize in a pressure cooker for 15 minutes at maximum pressure. After sterilization, if making slants, tilt the flasks to the desired angle and close them until the medium solidifies. To make Petri dishes, handle them carefully. If using sterile plastic plates, keep them closed until ready for use. In a space with surfaces cleaned with 70% alcohol, place the closed plates near a lit lamp to help maintain sterility. Open the flask with the medium, flame the rim, and pour the medium into the plate, closing it as quickly as possible. Let the medium solidify with the plate closed. In both cases, plate or slant, inoculate the medium with a sterile loop. If the loop is reusable, heat it in the flame until glowing and let it cool before contacting the yeast. Incubate the plates or flasks at around 28°C until the colonies reach the desired growth levels. Without a laminar flow hood, contamination can be tricky to avoid, so monitor the colonies closely.
2. With the plates ready, the second step is to sterilize the distilled water. The procedure is similar to that used for the medium flasks. In smaller flasks (between 10 and 15 mL), fill one-third with distilled water and leave the cap partially open. Using a support, place them in the pressure cooker and maintain maximum pressure for 15 minutes. Turn off the cooker, close the flasks, and let them cool. Following the same recommendations as before, with the lamp on, cut a piece of agar from the plate or slant with a sterile loop and place it in the flask with sterile water. Don’t forget to flame the flask rim. After closing the flask, seal the cap with parafilm and shake it. It can be stored for six months in a dry, light-protected place.

The other storage method described below ensures greater cell viability and longer stock duration. In this method, the yeast is slowly frozen using a cryoprotectant (glycerin), without liquid nitrogen, and kept in the freezer.

You will need:

• Glycerin
• Water
• Pressure cooker
• Flask with a cap that can be heated and placed in the pressure cooker
• Plastic tubes
• 70% alcohol
• Isopropyl alcohol
• Starter culture

To prepare the stock:

1. Prepare a starter culture and keep it reserved while performing the rest of the procedures. Clean surfaces with alcohol.
2. In a flask, make a 50/50 mixture of water and glycerin. Homogenize well and place it partially open in the pressure cooker at maximum pressure for 15 minutes. Turn off the cooker, close the flask, and let it cool.
3. Light the lamp and handle the plastic tubes near the flame. Fill half of each tube with 50% glycerin and transfer the liquid from the starter culture, leaving only the decanted yeast, filling the rest of the tube with this yeast. The final concentration of the cryoprotectant, which prevents ice crystal formation and cell rupture, should be 25%.
4. Place the tubes in a container filled with isopropyl alcohol and leave them in the freezer for 24 hours. This should ensure slower freezing, reducing cell viability issues. Afterward, you can remove the alcohol and store the tubes directly in the freezer.

I hope this brief text helps you with the storage and handling of yeast for your homebrewed beer production.

I have been storing my liquid yeast in the freezer using glycerol not glycerine. I believe that glycerine is actually harmful for the yeast. I have s similar processes on what is described and it works for me. I have around 12 types of yeasts in my yeast bank now

 

[BrewnWKopperKat]

Is this ai generated?

IMO, it's plausible that the content was AI generated - although there appears to be some edits in the original text.

 

[beren]

According to the internet, Modern use of the word glycerine (alternatively spelled glycerin) refers to commercial preparations of less than 100% purity, typically 95% glycerol.