Cultivating Liquid Yeasts
Homebrewers about to embark on the wonderful world of liquid yeasts, may be wondering how to maximize the use of each tube. Liquid yeast isn't as cheap as the dry variety and using it for a single batch can become costly. But don't worry, you can use each vial of liquid yeast multiple times, and build up a bank of different yeasts that you can use for your beers.
There are many ways to cultivate liquid yeast, in fact every brewer seems to do it slightly differently, but the method described below is loosely followed by most brewers.
Most of the equipment you need to cultivate your yeast culture is probably already hidden amongst your pile of brew gear or somewhere in the kitchen.
Equipment:
- 1 Bottle 3 - 5 L in volume
- Rubber Stopper
- Airlock
- Funnel
- 3L Saucepan.
- Sanitiser
- ½ Dozen empty stubbies and bottle tops
Ingredients:
Yeast Culture
500g Dry Malt
Procedure:
Cultivating yeast is not much harder than brewing beer, but the most important step is sanitation. However fastidious you are with your cleaning when it comes to beer, be twice as fastidious when cultivating yeast. One infected yeast culture now could potentially ruin each and every beer you make with that yeast.
If you use a no-rinse santiser, keep everything in the sanitiser until you need it. It's also a good idea to keep some sanitiser or pure alcohol in a spray bottle, so you can give things such as your bottle capper a quick squeeze as you use them. If you use bleach normally though, don't use it now - bleach kills yeast.
Step 1: Take your tube of WhiteLabs yeast, and let it come to room temperature.
Step 2: Measure out 55g of dry malt, and add it to 500ml of water. Put it on the stove, and boil for 15 minutes. This is essential to kill all bacteria in the water. Be carefull of boil overs - malt tends to suddenly foam up (called hot break) and creates a sticky mess.
Step 3: After the malt has boiled for 15 mins, put a lid on the saucepan, and immerse it in a sink full of cold water. Make sure that no water gets in the saucepan as this can infect the wort. You should stir the water gently, and swish around the hot saucepan to make sure that there are no hot spots left in the middle. You may also need to replace the water in the sink a
couple of times.
Step 4: Pour the cooled wort through your sanitised funnel into your sanitised bottle and put the stopper in. Now shake the bottle like mad for as long as you can. This helps to oxygenate the wort, which promotes healthy yeast growth (this also applies to your beer wort).
Step 5: Take the tube of WhiteLabs yeast, and give it a shake to make sure that all the yeast is in suspension. Wait a minute for it to settle down, and carefully remove the cap - if you remove it just after shaking it can foam out. Now carefully pour the yeast into the wort and place the stopper, and airlock in the bottle.
Step 6: After a day or so, the wort should be rapidly fermenting - you should see a larger amount of yeast on the bottom of the bottle, and you should have seen krausen (the foam on top) appear. You should now "step up" the wort to 4L over a couple of days, using the same boil, and cool procedure listed about. You can step up in 2L batches now that you have a healthy yeast culture to ferment it. Simply use 110g of dry malt per liter of water to make 1.040 wort. It is best if you pour the wort into an intermediary container and shake to oxygenate the new wort and then pour it into your culturing bottle.
Step 7: You should now have 4L of yeast and fermented wort to use. The best way to use this is to pitch it into your beer at high krausen - when the foam is at it highest, and the yeast are most active. Simply shake the bottle to get all the yeast off the bottom, and pour 2L of this solution into your beer in replacement of the dry yeast, and ferment as normal. 
Step 8: The remaining 2L of starter can now be stored for later use. Simply pour the solution into ½ dozen stubbies, cap and label them, and put them into the fridge. When you want to use them next time, simply follow the same procedure, but only make up to the 2L that you need.
