Propagating yeast from a Bottle-conditioned beer is relatively easy. You'll need the following before you start:
- An unopened bottle of bottle-conditioned beer
- 100g of dry malt extract
- A lighter
- A 1.25 litre jar or jug
- Dry or liquid pack of yeast on hand as backup
- An airlock that can fit on a beer bottle
- An airlock that can fit on your starter jar lid
- Five to Six days before your brew day, prepare 200ml of wort using 200ml water and 1 tablespoon of dry malt extract (you could probably also use dextrose or sugar as well).
- Boil it for 10 mins then cool to about 25C.
- Carefully decant all but the last couple of centimetres of beer from your chosen bottle, leaving all the yeast behind.
- Flame the top of the bottle to sanitize it. Then pour your 200ml of wort into the bottle, attach an airlock and agitate the bottle for 2-3 minutes to aerate it.
- Store the bottle in a cool place with an even temperature of around 20C (a hot water cupboard is a good spot).
- 2 - 3 days later, check that the culture is showing signs of activity. If it is, proceed.
- Prepare a 1 litre starter using 75g of dry malt extract. Boil the wort for 10mins and let it cool to around 25C. Pour this into your starter jug or jar
- Remove the airlock from the bottle, flame the top, swirl the bottle and then pour it into your starter jug/jar.
- Attach the lid with airlock and agitate the jug/jar for about 2-3 minutes.
- After about 2-3 days the fermentation should be active and ready to pitch into a 19 litre wort. Remove the airlock, flame the rim of the jug/jar. Swirl the contents and pitch it into your wort.
