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Leaving too much sugar behind

GigaFemto

Grandmaster Brewer
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I am doing partial mash in a bag in a cooler, and  I am reaching my volume and gravity targets while the sparge water is still indicating that there is a lot of sugar left in the grain. Here are the numbers from yesterday's brew: Mash 5 lbs grain with 7.5 qts of water (1.45 qts/lb) at 150 F for 45 minutes. Recirculate 2 quarts, then drain into the kettle. Add 6.5 qts of sparge water to cooler for a sparge temp of 165, let it sit for 5 minutes. Recirculate 2 quarts, then drain into the kettle. At that point I had about 3 gallons (my target) and a gravity of 1.049, but the last sparge water still had a gravity of 1.035. That tells me that even though my efficiency is high I am leaving a lot of sugar behind in the grain. What can I do to get that sugar to come out sooner? Less mash water and more sparge water? Let the sparge sit for longer? Sparge twice with half the volume in each?

This is a good kind of problem to have, and I could just ignore it, but the waste bugs me.

GigaFemto
 
Technically you should get 1/2 of your volume from first runnings and the other half from the sparge for optimum efficiency. In practice, I've found that very little is lost as you get away from that ratio within reason. If I understand your question, you're concerned that the gravity of your second runnings is higher than you expect.

The sparge is conducted to rinse sugars that remain in the grains after draining the first runnings. If you use less strike water and more sparge water the gravity of your second runnings would be lower due to dilution. That said, at 150 F I would mash for at least an hour. You may very well have had some conversion still going on between the initial runoff and the second runoff. You can do an iodine test to make sure conversion is complete as well.
 
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