Sourdough Blonde – An Adventure in Kettle Souring

Sometime last year Tim, the head brewer at the Dry Dock South, led me into the back and handed me a sample from one of the fermenters.  It was nice!  Tropical fruit flavors, some lactic smoothness on the tongue, tart and clean.  So I asked the secret and he told me, a pitch of organic yoghurt once the wort had reached 120 degrees then keep it warm overnight.  By morning the pH was in the 3.5 range.  From there, boil as usual.  So I tried it.

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This is Sourdough Blonde at eight days in the bottle.  Instead of the yoghurt pitch, I used a couple teaspoons of my sourdough starter as the lacto source.  She came out very nice, not as tart as Tim’s due to an error on my part, more on that later.  But the tropical fruits – pineapple and mango – are there, some malt flavor is still to be found despite the souring.  It has some body and is a pretty beer.  I’m happy with it!

My error was temperature control during souring.  I chilled the wort to 120 degrees, pitched my sourdough and insulated the heck out of the kettle to keep it warm.  By the next morning it was in the 90’s, warm enough for lacto but cool enough to allow some unwanted bugs to take hold.  So I started applying heat using a hot plate.  It looked as if all was well, the temperature was holding between 110 and 120 degrees F so I went to take a shower.  When I came back, it was 150 in the kettle, all my lacto were dead.  The pH had only dropped to around 4 but there was nothing to do other than to continue processing.

She came out good, though.  And I got a two-stage temperature controller so next time, the hot plate will cut off at 120 degrees.  More on kettle souring later. Here’s the recipe:

http://www.brewersfriend.com/homebrew/recipe/view/281435/sourdough-blonde

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