Remedies for under attenuation

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Remedies for under attenuation

Post  CGreen on Sat Dec 12, 2009 8:42 pm

We have all been there. The recipe says that our final gravity is supposed to get down to 1.012 but here we sit stuck at 1.022. What the hell can I do to prevent this in the future. There are many factors that affect under attenuation but I have a few tried and true remedies for you.

Rehydrate that dry yeast! I am not a fan of dry yeast but one thing that is critical for using dry yeast is re-hydrating prior to pitching. Only use sterilized water for this. Pitching dry directly onto the wort effects yeast viability and actually kills a significant amount of out little friends. Treat them right and they will treat you the same.

Pitch an appropriate amount of yeast. If math makes your stomach turn there is a link I will post after my explanation. Here is the short and sweet of it courtesy of Mr. Malty. For an ale, you want to pitch around 0.75 million cells of viable yeast (0.75 million for an ale, 1.5 million for a lager), for every milliliter of wort, for every degree plato. (0.75 million) X (milliliters of wort) X (degrees Plato of the wort). There is about 3785 milliliters in a gallon. There are about 20,000 milliliters in 5.25 gallons. A degree Plato is about 1.004 of original gravity. Just divide the OG by 4 to get Plato (e.g., 1.048 is 12 degrees Plato). So, for a 1.048 wort pitching into 5.25 gallons you need about 180 billion cells. (750,000) X (20,000) X (12) = 180,000,000,000. As promised, here is a link to a fantastic pitching rate calculator that covers all this dastardly math. [You must be registered and logged in to see this link.]

Aerate/Oxygenate that wort! Yeast use the oxygen in the development of their cell membranes. These cell membranes allow them to process sugar for food and grow. Without oxygen, yeast cannot synthesize sterols very well, which means they can't grow more cell membrane, which means they cant bud and reproduction diminishes. We need to provide the yeast with sufficient oxygen to allow them to grow quickly and reproduce when they are first pitched. The cheapest way to do this is to pour the wort into our fermenters vigorously. Dispose of the trub and hop bits from the kettle and pour the wort back into the boil kettle. Again transfer the wort back over to the fermenter, splashing as much as possible. Do this many times to achieve the desired concentration. Pitch your yeast and then shake the hell out of that fermenter for several minutes to distribute the yeast and aerate further. Another way to achieve this is with an oxygenation kit that can be found at many retailers [You must be registered and logged in to see this link.] (Bob can order you one as well). This is a diffusion stone that turns the pure oxygen into very fine bubbles. It is possible to put to much oxygen into solution which can make fusel alcohols and diacetyl. A general rule is that 1 minute of pure oxygen is all that is needed and will give you more oxygen into solution than any amount of shaking.

Late sugar additions for big beers. One issue with brewing those big Belgian beers is that if you add that sugar to the boil the yeast tend to get lazy and not finish everything that they would without the simple sugars present. Think of it like this, the maltose that is created in the mash is the main course and that sugar is the dessert. Given the choice, yeast will eat dessert (simple sugars) first and say they are to full to finish the main course (maltose). Deny them the dessert until they finish the meal. Remove the sugar from the boil and do everything else as usual. Once fermentation slows, boil a small amount of water and add the desired sugar to it until it melts. Allow to cool and add to your fermenter. The yeast will welcome this and wake right up to completely devour the sugars. I use this trick to dry out my Double IPA's and I have excellent results (1st place at the Chicago Beer Society's Spooky Brew Review Oct 09).

I hope these simple things help you in the future and I look forward to tasting your beers!
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Re: Remedies for under attenuation

Post  Scott_M_Bort on Tue Dec 15, 2009 9:43 pm

Great info.
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I find this works well, too...

Post  Whatever on Wed Dec 16, 2009 12:19 am

I could be wrong, but I have had quite good results with streaming Marvin Gaye through the brewery during primary fermentation.

I specifically pipe "Let's get it on" for the first four days...

...and if the fermentation is slow or stuck I switch to "sexual healing." Twisted Evil
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Re: Remedies for under attenuation

Post  CGreen on Wed Dec 16, 2009 12:45 am

LMAO!!!
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Re: Remedies for under attenuation

Post  BassClefBrews on Tue Jan 05, 2010 2:07 pm

To arerate, I bought a plastic paint stirrer from Menards for $2 that attaches to a drill. Very easy, as the power drill does all the work in minutes.
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