Brewing with Yogurt

 
If you want to sour a beer with lactobacillus, there are many ways to do it. One way is to pitch a culture from Wyeast or White Labs. Sour mashing is another technique you can use. Or if you're more daring, you can use yogurt!

For the 3rd Annual Portland Fruit Beer Festival, The Commons Brewery made Biere Royale, a sour spelt ale made with black currant puree. Sean Burke, The Commons' Head Brewer, soured the beer with lactobacillus. But in an unusual twist, he cultured the bacteria from Nancy's yogurt! 

I loved Biere Royale. It had great lactic tartness (bordering on sour) that nicely complemented the fruit. I was intrigued by Sean's yogurt technique as my previous attempt at a lactobacillus soured ale took over two years and I was less than satisfied. I hoped to replicate Sean's technique for a sour blackberry homebrew. I reached out to Sean in hopes of learning how he cultured lactobacillus from yogurt. Not only did Sean explain his process, but he also provided me with detailed step-by-step instructions!
 
Biere Royale.  Photo courtesy of The Commons Brewery

I learned a lot from Sean's instructions and wanted to pass them on so other brewers could benefit as well. Sean's complete instructions are listed below. Text in bold italics are my comments and provide context. So grab a carton of Nancy's yogurt, and read on!

Sean Burke (left) and Mike Wright, owner of The Commons
      

Brewing Sour Beer with Lactobacillus Cultured from Yogurt
Instructions by Sean Burke Head Brewer, The Commons Brewery

  1. A week or so ahead of the brewday I pull about 2 liters of un-hopped wort from whatever I am brewing (Urban farmhouse is perfect for this) and chill it down with a water bath to somewhere around 110 degrees. 
  2. I then take a spoon full of Nancy's Greek yogurt and pitch it into the starter. I have a stopper with an airlock and temp probe that goes down into the wort. I then hook up a heating pad to a temp. controller and set it for 100 degrees. That will sit for about 4 days at that temp. The key there is the relationship to acid production and temperature. The cooler you have it the longer it will take, but you don't want to go above 130 either or the lacto won't perform.
  3. I will then pipette out some wort and take a pH reading usually targeting around 3.5-3.8. I should mention lactobacillus prefers an anaerobic environment so I would avoid using the stir plate as that will oxygenate the wort. I have found that the stopper with the airlock helps to keep the O2 out. The other advantage to keeping it anaerobic is that it will reduce the chances of something else can growing in there. You are really just promoting the lacto to grow by giving it the perfect environment.
  4. On the brewday I will mash and lauter as usual and run all the wort into the kettle. I then run it through the heat exchanger to get the temp down to 125 degrees. I then take the lacto starter and pitch it in and then close up the kettle. I will do this on a Friday so that when I come in on Monday it should be at the desired pH which is usually 3.6. I will then turn on the kettle and boil for 90 min.
  5. One thing I have found with this process is that because we use a pilsner malt for our base malt, which has more DMS precursor we will get some DMS produced during the lacto inoculation because the wort is sitting there warm for an extended period of time. This is why we will give it a longer boil which will volatilize off the DMS.
  6. After the boil we run it into a fermenter and pitch a clean ale  yeast (Wyeast 1007) and start fermentation at 58 degrees. After 48 hrs I will let the beer come up to about 68 degrees and keep it there throughout fermentation. At that 48 mark which is usually high krausen, I add the black currant puree and let that just ferment out.
  7. As you can see, this is different than the approach you are suggesting taking (NOTE: I was planning to initially pitch lacto, followed by an ale yeast a few days later). I settled on this process mostly because we can get a clean sour beer in a very short amount of time. There are people out there that will pitch the lacto in a secondary situation. I know that this will work but one of the main reasons I don't take that approach is that we re-pitch our yeast. By boiling the wort with the lacto in it, it kills the lacto and allows us to re-pitch the yeast and not worry that whatever beer it ferments next will have active lacto in it.
  8. One method that might work well for you (NOTE: I initially planned to split my wort into two batches and ferment half with Wyeast Lambic Blend and the other half with the Yogurt Lacto culture) is to boil as usual, then when it comes time to chill it, run half your wort into a carboy at about 125 degrees and pitch the yogurt in there.Then the second half of the batch could get cooled down to a normal pitch temp and you could add the lambic blend. You could try to hold the yogurt half at about 100 degrees while it is souring, then cool it down to whatever pitch temp you have chosen for your yeast. Pitch the yeast and after high krausen you could add your fruit. I bet that would work quite well.
  9. One thing you will find is that it actually doesn't take much lacto to get the desired acidity. Lacto grows about 10 times faster than saccharomyces so it will take over pretty quickly and by under pitching you will be promoting ester formation which will give it more depth. I think that you really could just put it straight into a carboy and it would work pretty well. Just remember to try to keep the O2 out.
  10. I have found that the lacto strains we use will not actually ferment out the sugars in this short of a time. As in the gravity does not change that much. We use a couple of lactobacillus delbrueckii strains which I harvested from a bottle of German Gose for a different beer and I have found that the pre-boil gravity doesn't really change that much. Maybe 4/10ths of a degree plato. With the yogurt you have two different strains of lacto. One is lactobacillus acidophilus which is the one that is really good for digestion as it actually lives in our guts. The other is lactobacillus casei. I am pretty sure that this is the one that is more dominant in this method. It is a pretty aggressive lacto strain and has no qualms with consuming the sugars available in wort. If I remember correctly it is also homofermentative, which means it will only consume sugars and create acid as a byproduct vs. heterofermentative lacto strains which will consume sugars and not only produce acid but will also produce alcohol and CO2 therefore dropping the gravity more.

Armed with the knowledge behind Sean's technique, I gave it a try: 

  1. I made one liter of wort in a flask using 3 oz. of DME, cooled it down to 110º, and added about two teaspoons of yogurt.
  2. I placed the flask on a heating pad and set the temperature to high. Since I don't have a temperature controller, I just monitored the temperature of the starter and adjusted the heating pad controls to keep the temp in a 100º-130º range.
  3. After 32 hours, my culture reached a pH of 3.8, so decided it was ready to be unleashed!
  4. I originally planned to inoculate my wort with the yogurt lacto starter and add ale yeast a few days later. However, I decided to stick to Sean's method as it would enable me to control the level of tartness and then kill off the lacto in a long boil. It also provided of the benefit of brewing a "clean" beer without the worry of pesky lacto bacteria getting into places where they're not welcome.
  5. The next day was brew day. After the mash and lauter was completed, I divided the wort into two 3.5 gallon batches. I pitched the the yogurt lacto starter in half (pictured at bottom left). For the other half, I boiled and pitched Wyeast Lambic Blend. 
  6. Since my brewpot isn't insulated, I knew maintaining 3.5 gallons of lacto inoculated wort at 110º-120º for a few days would be a challenge. So I kept it in my oven. Every few hours, I heated it up to 170º for 30 minutes or so. This allowed me to maintain the wort at a temperature range of 95º-125º.
  7. After about 3.5 days, the wort had a pH reading of 3.6 and had a solid lacto tartness. I was very pleased with it and decided it was time to boil!

As an homage to Biere Royale, I've named my beer Blackberry Royale. It's happily fermenting as I write this. For more details, check out my Blackberry Royale brew log. I have high high hopes for this beer! More importantly, I'm thrilled to have learned a new technique that I'll continue to experiment with in the future.

Finally, a huge thanks to Sean for taking the time to document his method for me and for answering my numerous follow-up questions! If my beer turns out half as good as his, I'll be thrilled!

If you try this method, please let me know how it turns out!


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10 comments:

jared said...

Hi I'm in the midst of trying this and I was wondering how much currant (or blackberry?) puree you added to what volume of wort?

Sanjay R. said...

Jared, I added 15 oz of blackberries to my 3 1/2 gallon batch. The amount was a bit of a guess on my part. I wanted berry flavor, but I didn't want to go overboard and turn my beer purple. I'll post the details with pictures shortly. Good luck and please let me know how yours turns out!

Eric S said...

Great post, and very timely. I just brewed a beer based on The Commons' Myrtle. Similar, but I used lemon peel instead of the fruit. I pitched lacto in first, then added a saison strain after three days. I do want to try using this method as the yogurt strain produces more acid than the debruckii strain.

Sanjay R. said...

Thanks Eric. Please let me know how your Myrtle-inspired beer turns out. I have not yet tried a fermentation with lacto followed by ale yeast. I'm working to get my brew log posted, so you'll get to see my brewing and tasting notes. Cheers!

Chris Burgess said...

Thank you for this great post! Do you have any updates? I'm anxious to hear how it turned out (how sour it got and how quickly). I'm planning to do something similar myself, and would love to hear how it went for you. Thanks!

Sanjay R. said...

Thanks Chris! I haven not tasted it again, but expect it should be ready to bottle it soon. I need to get my brew log posted soon! Hopefully this week. Cheers!

Rachel said...

Amazing, never heard of this. Thanks for sharing!

Eric S said...

So the beer I brewed with the lacto didn't end up having any tartness. I suspect I didn't have it at high enough temperatures or the hops interfered with the souring. Hard to say. I'm going to try this technique soon. I'll keep you posted!

Chris Burgess said...

I tried a batch using the yogurt over the weekend. I was able to keep the starter and the kettle volumes both above 100F for three days. The pH tests look like the lacto did its job, both in the starter and in the kettle. It's fermenting now, and I'll be adding tart cherries and raspberries to portions tonight. It will be interesting to see how it turns out.

Sanjay R. said...

Chris, I bottled the beer and had my 1st carbonated taste. I'm happy with it. The blackberry flavor comes through and it has a moderate level of tartness. Next time, I'll let it get more sour.

Eric, sorry to hear it didn't sour as you intended. I really like the sour wort method. It allows more control of the level of sour and the wait time is short. I'll definitely to it again. As you mention, I think hight temp is key after initially pitching lacto.

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