How To Make A Bock Yeast Starter

I'm getting ready to make a chocolate bock recipe which is loosely based on the Sam Adams Chocolate Bock from their Winter Seasonal pack. To tell you the truth, I've never had a bock, nor have I had the Sam Adams chocolate bock. But my brother likes it, and I didn't have any other ideas for my next brew, so this idea was as good as any other!

The first thing I learned is that making a bock yeast starter is different from ale yeast starters.

The two main differences are:

1) A bock is a lager, which uses lager yeast. Lager yeast ferments much longer than ale yeast, and at a cooler temperature

2) A bock is a “bigger” beer, roughly meaning that it's going to be higher gravity, ie more sugars for the yeast to eat

Because of these two things, making a yeast starter is not an option. It's a MUST.

To tell you the truth, I only made my first yeast starter a few weeks ago on an Irish red ale. Previously I had used dry yeast once, and a vile of White Labs (the liquid kind) without making a starter. Both beers turned out good, but making the starter seemed fun and it also looked like it was something all the pros did, so I wanted to get in on it.

For this beer, I'll be using the WLP833 German Bock Lager Yeast from White Labs. Here are some things I learned, and some you should consider when making your first bock yeast starter.

Amount of Yeast

With ales, you can get away with one vile of yeast, but it was strongly recommend by the homebrew store that I use two vials for my starter. After reading up on the forums and other interweb sources, it's true that you are going to need a LOT more yeast to ensure a healthy fermentation.

I haven't done enough beers to screw up too badly and don't have a refined enough palate to taste much of a difference, but if yeast are stressed out from having too much work to do it can create off flavors. Make sure you get enough yeast into your beer, and double up. This also means you will need more dry malt extract, more water, and more yeast nutrient.

Amount of DME, water, and Yeast Nutrient

This is a big question for me, and I'll leave this open to comments if anyone has any experience with this. I received several suggestions from different sources, and I can't say which one is right. I can only say which one I did.

• The guy at the homebrew store told me one cup of water to 1/4 cup of DME (dry malt extract) and a bit of the yeast nutrient.
• The yeast starter instructions (from a kit I got with my Erlenmeyer flask) say 450ml water, 1/2 cup DME, and a pinch of yeast nutrient.
• Yet another measurement in a homebrew forum I saw says 1 quart water, 3-4 oz of DME, and does not mention the nutrient.

I can't say which is the most legit, or if it matters that much. I would guess that more DME is going to be better than less, but it's just a guess. For a double batch, I ended up with 900ml water (4 cups), 1 cup DME, and two pinches of yeast nutrient. It's kind of a mix of all of the above, but I think I might not have enough water. The yeast culture is growing, but I can't say if there are any issues at this point. Suggestions are welcome in the comments.

Yeast Starter Temperature

This is a debatable point, and I've heard of two ways to handle a lager yeast starter.

Method #1 Make the starter as normal, pitch at normal pitching temperature, and slowly bring the wort down to your desired fermentation temperature. For a bock (lager) this is going to be about 50 degrees F. This is what the guy in the homebrew store told me.

Method #2 Pitch one vile of yeast and start fermentation at room temperature for a day. Add a second pint of aerated wort and cool the temperature 5 degrees. Continue this process until you have enough yeast.

My Method: I pitched both vials of yeast and am fermenting them at room temperature for a few days. One day before I brewing I will put the starter in the fridge to cold crash the starter. As I will mention below, I need to decant this extra liquid from the wort to remove any off flavors before pitching into my beer. This will be much lower than the recommended 50 degrees, so about 10 to 2o minutes before I need to pitch I'll take it out of the fridge, bring the temperature up, and pitch at 50 degrees, the temperature needed for primary fermentation.

The advantage of pitching your starter at a colder temperature is clear. By starting warmer then going cooler, you are preventing the yeast from fully consuming the diacetyl they produced. By starting cooler then having a day or two of diacetyl rest after primary fermentation (before lagering) you can more efficiently remove those buttery flavors from your wort.

Length of Time Needed

Some places on the interwebs and within these ancient things we call “books” suggest that 12 – 24 hours is enough for a yeast culture to reach maximum cell density.

Others have reports of folks doing big beers and needing a full five days, including a day to cold crash.

I made my starter on Sunday. Today is Tuesday. I can still see activity going on, so I'm going to leave it until Wednesday night to see if I want to cold crash on Thursday, then brew on Friday, or cold crash on Friday and brew on Saturday. I don't know what the correct answer is, so this is just reporting what I'm doing and I'll follow up if I any exciting results are produced.

Cold Crash and Decant Extra Liquid

I've mentioned this above, I plan to cold crash cold crashed my bock yeast starter which will be first for me. Though I seemed to have used a lot less water than some places recommend, pretty much every source I've read has said that you should NOT pitch the whole vile of liquid for large yeast starters.

With smaller starters, for instance, with ales, the volume of starter wort to beer wort is very small, and any off flavors produced will not be able to be tasted in the final beer product. However, as your starter grows, the chance of affecting the final flavor of your beer grows.

The cold crashing is optional, but recommended in order to get all the yeast out of the liquid before decanting the unused wort. Either way, you want to get rid of as much of the excess liquid as you can before putting your awesomely huge yeast culture into your precious beer.

Lessons I Learned About Airlocks

I had always seen videos of guys using airlocks on their yeast starters, and thought it looked pretty cool. You know, sciency!

But Billy Brew convinced me than an air lock is not the best way to go. Remember, we want to give your yeast plenty of oxygen and allow carbon dioxide to escape in order to help them grow rapidly and easily.

Though a foil cover looks a bit tacky IMO, after removing my airlock and swirling the wort every couple of hours I could see much more activity and growth in the flask, and I'm of course happy with these results.

Further Reading:

How To Reduce Diacetyl in My Lagers

Wyyeast Pitch Rates

Homebrew Science | Diacetyl

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I haven't started my “Chocobock” quite yet, but will add it to my list of beers, including pictures and recipe once all that goes down later this week. If you have any questions, corrections, or personal experiences with bock yeast starters, feel free to leave a comment below.

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