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.
- 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.
- Tighten the cap, then shake the bottle vigorously for 30 seconds.
- Loosen the cap so fermentation products can escape.
|Step 1||Step 2||Step 3||Step 4|
|5ml Tube – 0.175 billion||Mix yeast and 250ml of 1.040 yeast in bottle – 3.3 billion||Add 1.5L of fresh 1.040 wort without pouring off 250ml wort: 1.75L – 40 billion||Sediment 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:
- 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.
- Prepare 1.5L to 1.75L of 1.040 wort as per the instructions above. When cooled transfer wort to your sanitized bottle.
- Pitch the smack pack/tube of yeast into the starter. Immediately shake vigorously to oxygenate and mix-in the yeast.
- Follow the steps outlined in the video to grow the yeast.
- Sediment & pitch the yeast.