Thursday, November 15, 2007
Magnetic Stir Plate
This is one of the better brewing investments I've made in the last year. The magnetic stir plate is very good at kick-starting the beer yeast. I typically create 2 liter yeast starters from a single pack of liquid yeast.
I have three erlenmeyer flasks, in 1 liter, 3 liter and 5 liter sizes. The 3 liter one can be seen in the photo above.
Creating the yeast starter is straightforward: Fill the flask with water from the tap. Put it on the stove, turn on the heat and wait until the water heats up. Then add 1 tablespoon of dried malt extract per dl of water. Then add 1/2 teaspoon of yeast nutrient. Stir well and let it boil for about five minutes in the erlenmeyer flasks. This makes sure that both the yeast starter and the flask is properly disinfected. Cover the opening of the flask with aluminum foil or plastic wrap to prevent things from falling into the pristine wort. Cool it down to about 20 degrees C in a cold water bath before adding the yeast. Then spray the scissors and the opening of the yeast pack with a strong alcohol solution to make sure that no bacteria gets in contact with the yeast on its way to the yeast starter. Wait for the alcohol to evaporate before opening and pouring the yeast into the erlenmeyer flask. Finally, add the stir bar (make sure that it is disinfected) and put it on the magnetic stirrer. The stirring will provide the yeast with lots of oxygen.
It usually take a day or two before the yeast has fermented out the yeast starter.