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Batch Sparge Ah Ha Moment

MikeinRH

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I have no patience when it comes to sparging 10-gallon batches. After running off wort from the lauter, I usually add back an equal volume of water to the mash and let it sit. I heat the water to 150-160 degrees before adding to the grain bed so I reduce the risk of importing any tannin. The longer I let it sit, the darker the runnings into the kettle. (Ah ha!) I've been told that, prior to the boil, there's really no harm in letting the first runnings sit in the kettle. Nevertheless, I fire up the kettle and wait for the first runnings to nearly come to a boil before adding the sparge to achieve my target kettle volume.  I suspect that letting the sparge sit a while contributes to a higher OG, though I've never taken the measurements .. yet.
 
Mike-

I've taken those measurements, both during the mash and during the first sparge.  My experience has been that there is a much more significant increase in SG in the mash than there is in the sparge.  There is an increase in SG of the second runnings while sitting in the MLT, but it is relatively minor (2-3 points). 

This makes sense because the vast majority of the enzymes were removed from the MLT with the first runnings.  In other words, they were already disolved into the wort.  The only enzymes available to continue conversion during the sparge are those that were retained in the grain. 

It would be reasonable to estimate the enzyme quantity similar with the maltose quantity.  Assuming equal volumes for first and second runnings: 2/3rd of the maltose is removed in the first runnings, with 1/3rd in the second runnings.  Since the average diastatic power of modern base malts is about 4x that required for self conversion (at 120 degree lintner), that should mean that there is still 40-50 degree lintner left in the MLT for the second runnings (however, in reality the diastatic power of the mash is the weighted average of the entire grain bill).  So, theoretically, there is still enough enzymes for continued conversion.  However, with only 1/3rd or so of the enzymes left...you would expect there to be a commensurate drop in the rate of conversion. 
 
Tom - Does this make a case for eliminating the sparge altogether?
 
Er....no.  The sparge is removing sugars that have already been formed by the mash.  This is just a case for asserting that the sparge is not an extension of the mash----further conversion is not going to take place after you have rinsed the first runnings away because the bulk of the enzymes went into the kettle with the first runnings. 

So, if you need additional conversion then continue the mash for up to 90 minutes of total mash time (for temps above 145F).
 
Tom - Does this make a case for eliminating the sparge altogether?

Not sparging is basically BIAB. In BIAB you have to use more grains to achieve your gravity target. Like Tom said,you sparge to rinse the remaining sugars that are still clinging to the grains. The only way I can think of gaining more would be if you mashed at a lower temp say 149F and add more water to bring mash up like 156F.  Even then it might not be much. You can go up in temps during mash, but you can not go down. The simpler sugars converted at the lower temps has been stopped as temps rise. What is you brew eff, and your Mash eff? It sounds to me you might be using a larger grain bill to hit you target gravity. I batch and fly sparge, both ways it takes me 45 mins to an hour to sparge. I seldom come up short at 72%Brewhouse eff. Do you take a preboil gravity check and compare it BS2 to see where your at? It might tell you how you did on you first run off.

 
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