Yeast Harvesting and Banking made simple.

All homebrewers, especially in India have one thought constantly haunting them. 'What if I run out of yeast?'
Worry no more!! This post will get you sorted with all your special yeast strains. I will be explaining the methods I use to harvest as well as preserve yeasts. I have got inputs from professional microbiologists and anaerobic experts to make yeast banking efficient. This method has been tried and tested successfully by me and a few other homebrewers I know. Following the steps correctly will ensure contamination free yeast harvest and preservation.

Why do you need Yeast Banking?

  1. You'll be saving a Lot of money on yeast.
  2. Only the healthiest yeast will survive harvesting. Dead yeast cells make excellent nutrient for the rapidly multiplying daughter cells.
  3. Large variety of special yeast strains can be stored for extended periods of time (cryo-preservation).
  4. You don't need to depend on anyone for your yeast supplies, except to acquire new strains.

Supplies

Make sure you have all the supplies in place before you attempt to preserve the yeast. Preparing beforehand will ensure a hassle free process right till the end.
Below is the list of supplies you'll need (In order of importance for each procedure.)

Yeast Harvesting

  • Source of sterile water (Aquaguard with UV filter is what I have. You can use boiled and cooled water too.)
  • StarSan (or equivalent) sanitizer solution
  • 4-6 qty of Mason Jars / Glass bottles with wide mouth / Screw top glass containers
  • Space in your refridgerator 
500 ml Jars I use to collect slurry


Yeast Banking
  • 10ml Syringe
  • 15-50ml Vials or HDPE/LDPE containers (you can get it from a local Lab Supplier)
  • Pure Glycerine (available at your nearest medical store)
  • Ziplock bags
  • Space in you Deep Freezer (as close to the cooling fan as possible)


125ml HDPE screw top bottles I use for cryopreservation 


DIY ice packs. Select appropriate size zip lock bags according to your freezer size. Fill it up till 1/3rd mark, add a pinch of salt, shake well till it dissolves. While sealing, make sure to get air out of the bag. Freezer it flat down and then its ready to use.

Previously I used 50ml Vials but it used to be a problem because they are not flat bottom.

My present cryopreservation setup. Ice tray, ice packs, storage containers. Ice packs are used to keep temperature constant when the freezer is running the Defrost Cycle. Its better to have a few ice packs covering the top of storage container as well.


The Procedure

Yeast Harvesting
  1. After you are done with primary fermentation, leave the slurry within the fermenter. Take about 1 Litre of sterile water and pour it in the slurry.
  2. Close the lid/stopper of the fermenter and shake it well. This will make sure all the yeast comes into suspension.
  3. Sanitize your Mason Jars (about 5-6 nos. More the number , more yeast you can harvest. I usually use 3 x 500ml Jars as displayed above). Add this slurry into the Mason Jars and let it settle in your refrigerator for about 2-3 hours.
  4. After 2-3 hours in the fridge, you will see 3 distinct layers formed in the jars. The uppermost layer is just beer and water. Middle layer is Yeast which you need to harvest. Bottom most layer is waste hops and trub.
  5. Take a couple of new Jars and sanitize them.
  6. Now you need to decant beer from the previously filled jars. Basically, you should pour off the top layer, leaving behind middle and bottom layer undisturbed. Do this for all slurry filled jars.
  7. Next, line up the fresh set of jars. You need to pour the middle layer (suspended yeast) into freshly sanitized jars. (Suspended yeast layer from approx 3 jars should fill up 1 new jar. This new jar is the fresh yeast you harvested).
  8. Throw away the bottom layer as this is just waste hops and trub.
  9. Allow the jars to settle overnight in the fridge. After about 8-10 hours, you should see a thick creamy white sediment at the bottom, while rest of the jar is full of clear beer.
  10. If you are really up to the task, you can pour away the clear liquid leaving just enough beer to stir up the sediment. 
  11. This thick sediment is highly compacted with fresh yeast cells. You can distribute them equally in containers/vials and store them in refrigerator for future use; or you can preserve a few containers in the yeast bank.

Note: 

The more you concentrate yeast slurry by pouring off clear fluid, the more yeast cell count you get in final sediment. This is scaling up the sediment concentration. Which translates into the following: 
  • Step 1 you had 6 mason jars. (Slurry = Beer + Yeast + Trub)
  • Step 2 you concentrated yeast layer, so you got 2 jars of yeast
  • Step 3 you poured away the clear beer leaving behind yeast sediment
  • Step 4 you distributed it in containers/vials for storage(This is pure yeast)


Every time you take out a container for pitching, make sure you make a starter. A Stir Plate will help you get max cell count in minimum time possible.

After you make a starter with DME, reuse some yeast from this starter for storage. Repeat this procedure whenever you make a starter. That way hops and other material don't come in contact with yeast cells reducing the chance for yeast mutation.

"For the first time, harvest the yeast from primary. Next time onwards, harvest and re-harvest yeast from the starter."

Yeast Banking:

  • If you decide that you want to store some yeast for long term preservation, yeast bank is the answer. You need Glycerine, a sterilized syringe and a sanitized container ready before Step 4 (highlighted above.) 
  • Use 10-15% Glycerine per container. That is, if you have a 50 ml storage container, take 5 ml of pure Glycerine and add it in the storage container. Fill the remaining volume with yeast slurry(Step 4) and shake it well.
  • Make sure you fill the storage container only upto 80% of its capacity because freezing will cause expansion of water. 
  • Label and the put it in the freezer (-5 to -12 C) immediately and surround it with ice packs. 

Use of Glycerine:
It is used to dehydrate the yeast cells without killing them because ice crystals will rupture yeast cells immediately. Adding glycerine prevents the cells from freeze burns. You can store yeasts for 3-4 years easily using this method of 15% glycerine + slurry.

In case you ever decide to use a frozen yeast culture, simply take the container and place it in the refrigerator for a day. This prevents sudden change in temperature. After about 24 hours, bring the storage container at room temperature and then pitch it in the starter.

This is the entire process I follow. It has been tried and tested by a few other homebrewers and works well. I know it will be a little difficult to follow at first, but go through the entire procedure a couple of times and you should get the hang of it. I have cryo-preserved about 14 different strains using this process.

If you have any queries please let me know in the comments section.

Happy to help.
Cheers!


16 comments:

  1. Thanks Ameya for posting such a detailed write-up on yeast harvesting & banking. I have always wondered how it is done but never bothered to read up on the same. But this write-up cleared all my doubts! Cheers!

    ReplyDelete
  2. THANKS AMEYA FOR A NICE ARTICLE ON YEAST HARVESTING.HAVE A QUERY IN MIND I BREW FROM GRAIN AND ALWAYS USE POWDERED YEAST AND HYDRATE IT BEFORE PITCHING INTO WORT.
    IF I AM GOING TO USE THIS HARVESTED YEAST WILL THE AMOUNT OF YEST REQUIRED WILL BE SAME SAY FOR EXAMPLE IN SOME RECIPE POWDERED YEAST REQUIRED IS 4 Gms NOW WILL 4Gms OF THIS YEAST WOULD BE REQUIRED OR SOME MORE OR LESS QUANTITY WOULD BE REQUIRED ???? AND ALSO I DON'T WANT TO USE STIR PLATE WILL THIS YEAST CAN BE USED THE SAME WAY AS THE POWERED YEAST LIKE I AM HYDRATING IT NOW BEFORE PITCHING.

    THANKS

    JATIN(jatin.maggu@gmail.com)

    ReplyDelete
    Replies
    1. Using dry yeast and liquid yeast is totally different. When using liquid yeast always make sure your are using the slurry that has settled below. As a rule of thumb for new brewers always use 5ml slurry for every 1L of wort with OG less than 1.050. Which means if you make a 10L batch, you will need 50ml of 'Slurry'.

      About the stir plate.
      I would recommend you to use a stir plate as that will help you get a better cell count and healthy cells as they will always remain suspended and in contact with oxygen which is crucial for yeast cell multiplication.

      P.S : Do not use Caps Lock on every word you type.

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  3. Thanks a lot for the reply almost all my doubts have been cleared have ordered all the things needed for stir plate and one things is still in dark that how much amount of this sediment yeast will be needed to make a starter like in my above comment I said I need powder yeast 4 Gms how much this yeast would be required for the same recipe.
    Thanks
    Jatin

    ReplyDelete
    Replies
    1. For the calcualtions, I suggest you use a Yeast pitch rate calculator. Makes life very simple.
      E.g. -
      http://www.brewersfriend.com/yeast-pitch-rate-and-starter-calculator/

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    2. Hi, I have mentioned in my previous reply about the amount of slurry required while using liquid yeast. "As a rule of thumb for new brewers always use 5ml slurry for every 1L of wort."

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  4. After a successful first batch of Pale Ale, I am into my second batch. This time I shall try out Yeast Harvesting & Banking. One thing I still have doubts.

    I want to know, how to 'reuse some yeast from the starter for storage' or how to 're-harvest yeast from the starter'.


    ReplyDelete
    Replies
    1. Its very easy. Let's consider that you have made 1L stater and you get 100ml of slurry. Now the best option is to split this 100ml slurry into 2 parts; one for pitching and other for storage. For pitching you will need about 80 ml of slurry, while the remaining 20 ml can be used for storage. If you are going to make back to back batches, you can use this remaining 20ml slurry and make another stater out of it. This process is a continuous cycle.

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    2. Thank you, I understand. I have another query.. regarding wort temperature to be maintained while making a starter from a slurry. Is it necessary to put the stir plate with the starter batch in the temperature controlled refrigerator (18-23 *c). I am asking this because the room temperature now-a-days in Kolkata is around 32*c.

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    3. It's not necessary to keep the starter in a temperature controlled room/chamber. Higher temperatures create more off flavours and produce fusel/higher alcohols. As far as starters are concerned, we will be decanting(throwing away) the liquid and will be using only the slurry, so it's all good and you don't need to worry.

      If you are truly concerned about the temperature, you can cover the flask with a damp cloth and keep spraying water (every 5-6 hours) to keep it cool.

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    4. Thank you. My doubt is cleared.

      I will be trying freezing yeast for banking this time. On one point I need a little clarity. The vegetable glycerin I have is 100% pure. The yeast slurry needs 10-15% glycerin. For a batch of say 50ml of yeast slurry, shall I use 5-7.5ml raw glycerin and swirl the vial to mix it, or shall I make a 20-30% glycerin solution with sterile water and mix 50:50 of yeast slurry and this glycerin solution, which will eventually give 10-15% glycerin.

      Keeping in mind the contamination issues, which method do you thing we should follow.

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    5. I personally use 7ml Glycerin, add the slurry directly and shake crap out of it; this way I'm sure that it has mixed well.

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    6. Thanks... and before starter making, do you increase the vial temperature slowly by placing it in the refrigerator and then bring it to room temperature, or increase the vial temp. fast by putting it 32-35*C temp. water.

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    7. From the freezer I transfer the vial to the fridge (5-8C) for 24 hours. Before pitching the vial, I keep it at room temperature for 4-5 hours. This prevents rapid temperature fluctuation thereby reducing stress on the yeast.

      I have mentioned the exact same process in the last section of the post titled "Use of Glycerin"

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    8. Thanks again.. I am sure many of us will be benefited from these conversations.

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  5. This is a very nice explanation. please correct me if i understood correctly. i have my yeast in slant culture (pure culture). i will prepare about 500 ml of starter i.e 100 g DME in 1 L water, (is dextrose required) boiled. i add approx 5 ml cool sterilized wort to single slant scrape th yeast culture and pour it into 500 ml wort. grow under stirring condition 25º C for 24-32 hrs. let it settle in referigerator. decant the top layer and then use yeast sediment directly or give it a wash with sterile water and then use that sediment for glycerol banking. please guide. and for batch you suggest 80 ml slurry for pitching whereas my search lead to 2 L of starter for 20 L batch and i pitch about 175-200 ml slurry. can you please let me know what to follow. am i overpitching then.

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