Monday, 11 March 2013

Video: Budget Yeast Starter System

A few weeks ago I posted a video & blog post on how to take yeast from a yeast bank and grow it upto amounts that can be used to start a 20L/5 US gallon batch of beer.  However, that video used equipment that not all brewers have - namely, a stir-plate and flask.  Not all brewers will want to make the investment into these items - especially if new to the hobby.

Luckily, there is a way for them to step-up yeast with zero investment - all you need is an empty 2L soda bottle and a funnel.  The only downsides to this method are a) you produce ~30% less yeast per step, and b) you must remember to manually oxygenate the yeast several times each day.

Important Note: The numbers and stages of this starter are based on the amount of yeast brewers receive when they get yeast from my yeast bank.  If you are starting with a wyeast smack-pack or white labs tube the process is slightly different; instructions for this can be found at the end of this post.


Below the fold you will find a couple of tables to help you determine how many steps, and what step sizes, you need to produce the number of yeast you require.

All tables assume that your are are made of S.G. 1.040 wort, which can be prepared by mixing 1g/10ml (10g/100ml, or 25g/cup) of DME in water.  All starters should be simmered for 15 minutes and cooled prior to use.  A simmer is all that is needed - avoid hard boils as the evaporation loss can be enough to produce a wort that is too concentrated for ideal yeast growth.  If you over-boil, you can replace the missing volume with an equal amount of water that has been boiled for 15 minutes.

Each step needs to grow for 24-48 hours, until the wort is brownish-yellow with yeast. During fermentation make sure the bottle cap is on loose - this will allow the CO2 produced by the yeast to escape.  Failure to do this can result in exploding bottles.  At least four times each day you need to oxygenate the wort.  This is simply done:
  1. Squeeze the bottle to expel the air in the airspace above the wort.  Then let the bottle re-expand to draw in fresh air.  There is no need to remove the cap for this step; it simply needs to be loose.
  2. Tighten the cap, then shake the bottle vigorously for 30 seconds.
  3. Loosen the cap so fermentation products can escape.
The more often you perform the above procedure, the higher your yeast numbers will be.  The below tables assume 4-6 shakings per day.

Step 1Step 2Step 3Step 4
5ml Tube - 0.175 billionMix yeast and 250ml of 1.040 yeast in bottle - 3.3 billionAdd 1.5L of fresh 1.040 wort without pouring off 250ml wort: 1.75L - 40 billionSediment yeast in fridge, decant old wort, and add 1.75L of fresh 1.040 wort - 160 billion

If brewing an ale with a S.G. of 1.060 or less you only need to complete step 3 - there is enough active healthy yeast at the end of this step for a beer of this strength.  Completing step 4 provides enough yeast for most ales and lagers upto 1.060.  A 5th step can be added, providing 350 billion yeast - more than enough for 20L of any beer.

Important Note on Yeast Numbers: Previously I had a few emails enquiring about the yeast numbers I have recommended.  Conventional pitching guides recommend 0.75 million (ale) to 1.5 million (lager) cells per millilitre per degree plato, which works out to about 2X the numbers of yeast recommended above.  The 'traditional' numbers are based on pitching yeast from yeast-cakes, which are less hardy and active than those produced using the semi-aerobic growth of a shaken culture.  As a rule, you should halve the number of yeast you pitch when using high-quality cultures like those produced using a stir plate, hence why the numbers in the above tables are ~1/2 that normally recommended.

Starting with a Wyeast or White Labs Pack: The multi-step procedure outlined above is intended to grow very small amounts of yeast into pitchable quantities.  White lab tubes and wyeast smackpacks large amounts of yeast already, and as such do not require as complex a starter process.  In fact, the amount of yeast in these packages is equivalent to the double the amount you would expect to have after "stage 3" outlined above.  In essence, you are moving immediately to "step 4" as described above:

  1. If using a wyeast smack pack, smack it as per maufacturers instructions and let it grow for 12-24 hours.  If using a white labs tube go immediately to step 2.
  2. Prepare 1.5L to 1.75L of 1.040 wort as per the instructions above.  When cooled transfer wort to your sanitized bottle.
  3. Pitch the smack pack/tube of yeast into the starter.  Immediately shake vigorously to oxygenate and mix-in the yeast.
  4. Follow the steps outlined in the video to grow the yeast.
  5. Sediment & pitch the yeast.
This process should yield about 240 billion yeast - more than enough for most ales and lagers.  If larger numbers of yeast are required the sedimented yeast can be re-suspended in fresh wort and run through this starter process again, yielding roughly 400 billion yeast; enough for any 5 gallon batch of beer.

6 comments:

  1. It looks like you have the cap on tight when you put it in the fridge to settle. Is this correct, or should I let is breath in the fridge too?

    I am at 48hrs. and activity is starting to slow. Should I keep going another 12-24hrs? or have I grown enough yeast for my starter?

    ReplyDelete
    Replies
    1. I did have the cap on tight, but that was a mistake. You want to keep it loose, just like on the counter, for at least for first 8 or so hours in the fridge - if there are any residual sugars the yeast will consume them, pressurizing a tightly capped bottle. By letting it cool first you avoid the potential issues that may create.

      I'm assuming you pitched a wyeast or white labs tube into your starter? If so, at 48 hours you should by ready to go to the fridge; small amounts of activity can continue for a long time, but that residual activity is not making more or better yeast. 24-48 hours is typically sufficient.

      Good luck!

      Bryan

      Delete
  2. How about using dry yeast? In which step I need to start.
    Thanks

    ReplyDelete
    Replies
    1. Starters are not generally required for dry yeast; rehydrate in bottled water for ~15 min at 25C (or as per manufacturers' instructions), and add to your beer.

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  3. AS FAR AS DRY YEAST IS CHEAPER,CAN WE FOLLOW THE ABOVE PROCEDURE STARTING WITH DRY YEAST?

    ReplyDelete