Unless we are pitching dry yeast, starters are built from a liquid yeast pack we buy from our LHBS or from a vial in our yeast library. Typically this is done a day or two before the brew so that the starter is healthy and at peak activity when pitched and can immediately start chewing through the wort sugars.
Coming up in four days is our first lager brew: a 1.093 OG (8.9% ABV) monster, with a fermentation temperature around 52 degrees. Since this is such a beast and fermented cold, a substantial starter of around 694 billion cells is needed, plus about 50 billion extra to stash in the library for next time. With this much yeast to create, either a multi-step starter or a massive one will need to be created. Generally, we’d like to avoid multi-step starters because of the time involved in cold crashing each step, and also having many more places for the starter to go wrong or be contaminated. This means the option we’re going to pursue is a big 4.25 L starter.
The yeast selected for the Dopplebock is White Labs WLP833 German Bock Lager Yeast which should provide decent attenuation and a strong malty character. Since it’s the first lager for Monocle, we want to have a well-balanced, easy to use yeast. The hope is to also use this same yeast for a future Pilsner and other lagers down the road.
The process for this is basically the same as with any other starter: heat water and DME, add yeast nutrient, and put it on a stir plate for a couple days. The difference from how we typically make a starter is from the large volume that we’ll be stirring at once. Typically about 1/3 headroom in the stir flask is suitable to allow for krausen, but since there isn’t a 6 or 7 L Erlenmeyer handy we’re going to be making a “kettle starter” using a 2 gallon aluminum cooking pot. Since aluminum isn’t magnetic, the stir plate has no trouble spinning the stir bar inside (this should be tested first with water).
The following equipment will be used:
- 2 gallon or greater aluminum kettle (or any non-magnetic flat-bottom vessel)
- Stir plate
- Stir bar
- Star San, lots of Star San (in a spray-bottle)
- Disposable gloves
- Thermometer (way easier with an IR)
- Strong magnets (to attach to stir bar so that it can be kept somewhere)
- Bowl for Star San (put stir bar, scissors, etc. in here)
- Fermentation refrigerator (or semi-stable area around 70 F)
Also, the starter ingredients should be gathered up:
- 4.35 L water (100 mL extra for evaparation, spillage, etc.)
- 475 g DME
- 2.2 g yeast nutrient (strongly recommended)
- 2 drops Fermcap-S
A bowl should be filled with Star San solution and used to sanitize the equipment: stir bar, scissors, whisk, hands, and anything else that will fit into it
The kettle needs to be sprayed with Star San.
The work area should be cleaned up and everything gathered at hand that will be needed.
Making the starter
As usual, the BrewUnited Yeast Calculator was used and our starter recipe calls for 4.25 L water and 475 g DME. Additions will include a drop or two of Fermcap-S to prevent boil-over and 2.2 g of yeast nutrient. Use the calculator to figure out the precise amounts of water and DME for your own situation.
The water, DME, yeast nutrient, and Fermcap-S are put into the sanitized kettle and boiled gently for 10 minutes. After shutting off the heat, Star San is sprayed all over the kettle. A sheet of sanitized heavy-duty aluminum foil is used to cover and crimp as tightly as possible around the lip of the kettle to prevent anything from getting in or out during the cooling process.
Note: When making a normal starter, the Erlenmeyer flask is used to boil the starter wort and reaches temperatures sufficient to kill most things so pre-sanitizing isn’t necessary. Since aluminum is a poor conductor, the top of the kettle will likely not reach temperatures hot enough to wipe out everything, so pre-sanitizing is a necessary safety step.
From this point on, Star San should be used liberally and disposable gloves worn. To cool the kettle, fill a sink about 1/3 of the way and place the kettle with foil cover gently into the bath. Every 10 minutes or so, change the water until about 100 F wort temperature is reached. Then, the same procedure can be continued but blue ice packs added to the bath to assist in cooling down to 70 F or 75 F for pitching the yeast. Care needs to be taken not to slosh the contents of the kettle or the sink too much.
It’s also perfectly fine to leave it covered on the stove for hours until it’s naturally cooled off, or put it into the fridge or freezer. The only thing to consider is that the faster you can get it to pitching temperature to put the yeast into it, the better. There are plenty of other microorganisms that would love to eat the sugary wort, so getting the yeast in there quickly allows them to dominate and produce alcohol which will also help fend off those other creatures.
Now that the wort is ready to have yeast pitched into it, the sanitized yeast packet needs to be quickly cut open with sanitized scissors and dumped into the kettle. Add a sanitized stir bar and use a new sheet of sanitized heavy-duty foil to cap off the kettle and allow for air exchange during yeast growth. Minimize the time that the kettle remains uncovered since that makes it more susceptible to a wild yeast infection.
Place the kettle on a stir plate inside of the fermentation refrigerator for two days at 65 F. Books can be used to extend the top surface of the stir plate so that the kettle doesn’t tip over. You can also ferment just fine at ambient temperature (around 70 F +/- 5 degrees), just watch out for krausen overflow. This provided a good growth rate without being too hot which got the starter to full growth in a couple of days.
Note: If you get an overflow situation and it ends up being a mess, spray everything with Star San, get another sanitized container that can hold some of the starter, and pour some of it off. Let them finish fermenting without a stir plate and proceed as normal.
Once the yeast are done, place the kettle in a regular fridge for two days and decant the liquid once the yeast have settled out to get rid of the excess liquid. We don’t want 4 L of weak starter watering down the rich Dopplebock wort! Make sure to spray the inside and lip of the kettle with Star San before pouring anything from the kettle. The remaining slurry will be warmed back up to pitching temperature, 48 F for the Dopplebock, before pitching into with the wort. Additionally, 285 mL of slurry will be separated and cold-crashed for the yeast library.
It’s not really any more difficult to make a large starter in a kettle, other than some extra care must be taken to ensure that no contamination happens and you must be able to facilitate the complications from having a larger stirring container. It’s worth building a yeast kit to make the starter building process easier if you find yourself making them often regardless of how large or small they might be. With a bit of extra caution, your yeast can grow happy and healthy to make some great tasting beer.