Well, I racked the Maibock from the primary fermenter(6.5 gal carboy) to the secondary (5.5 gal carboy)today. It has been been fermenting strongly for the past 10 days at around 48 degrees and has showed signs of slowing down in the last 24 hrs, so I thought this would be a good time to rack it off and warm it up to 59 degrees(the ambient temperature in my basement) for a 2-3 day Diacetyl rest before putting it away to lager.
Diacetyl is a natural chemical by-product of fermentation. The problem is that it produces an off flavor that is said to taste buttery or like butterscotch even in small amounts. Diacetyl is actually what they use to make butter flavored things that don't actually use butter. While this flavor might be OK in small amounts in some styles it is not acceptable in most. Yeast will usually absorb this chemical when fermented at warm temps so this not a problem with ales, however since lagers are fermented cold a Diacetyl rest is usually used at the end of the fermentation to "clean up" the Diatetyl. So, the Maibock will sit at 59 degrees in the basement for a few days to finish up fermenting and then I'll cool it back down and lager it. While transferring, I took a sample to see how far along it is and as you can see in the pic below it is down to around 1.021. This is good news as it started at around 1.070. The finishing gravity for this style is from 1.012-1.020 so its right on target.
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