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Spunding valve experience

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I have been using a spunding valve set up for a variety of ferments and would like to see how many others have used this an get there thoughts. for all you that have no idea what I am talking about I will explain in another post in this thread.

A spunding valve is a means of fermenting under pressure to carbonate your beer during primary fermentation. A spunding valve consists of an adjustable relief valve that is attached to the fermenter. The assy may or may not have a pressure gauge attached.

faster delivery of product from kettle to glass

cons -
Must have a keg or other pressure vessel for fermenting.
Need to have a method of controlling krausen to prevent foam in the valve

issues -
CO2 toxicity to yeast

My first experience with this process was with a standard gravity blond ale. I did a side by side test with a fermentation by spunding and with a carboy. The fermentations for both were finished with in a day of each other. The spunding fermentation was cold crashed then counter pressure transfered to an other keg. Fully carbonated and ready for service on Day 6. The carboy fermented batch was racked to a keg and force carbonated for 3 days. A side by sided tasting showed that the spunding fermented beer was a bit sweeter although it did not taste under attenuated. The FG on each was within .002 (spunding 1.014, carboy 1.012). I use this process mainly for low gravity(1.040 SG) selection that need to be on service quickly (Bitters and other session beers). The use of CP transfer to another keg also ensures no O2 pick up during packaging.

Matt B:
I have not, but what has your experience thus far been as far as your attenuation? Does it attenuate as much as you would expect? Any noticeable sweetness or maltiness in the beer? How about any off flavors from yeast autolyisis?

The yeast toxicity and autolyisis (I read somewhere that while transferring to secondary in small volumes isn't necessary to avoid autolyisis, commercial breweries do it as the additional pressure from hundreds of gallons of beer sitting on top of a yeast cake promotes autolyisis, I forget where I read this though) are the only issues I could think of for why this would be a bad idea, that and the difficulty of getting a gravity reading out of carbonated beer :)

I've thought about doing something similar in secondary fermentation in a keg, but total attenuation being possibly sacrificed, then getting that valve plus the extra sediment in the keg turned me off to the idea.

With only .002 difference from a non-pressurized ferment it is not far off from what I would consider reasonable. I have since oxygenated more to get a higher cell count for more complete fermentation. I also rack after 4 or 5 days so autolysis is not an issue.


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