Batch sparging on belgians/low mash temps

I'm being lazy and not doing my searching, but ah well. Are there any concerns with batch sparging when you're doing a belgian/dry beer and mashing at a low temp? Generally I mash for ~60 minutes, collect, batch sparge as close to 170*F as I can get and let it sit for 10 minutes, collect again. Will that bring more unfermentables out of the grain than I would want for a dry beer?

I don't think so since the high temperature is supposed to halt enzyme activity. If you're worried though, couldn't you just use a lower sparge temp? I think the only reason higher temps are used is to halt enzyme activity and further thin the wort to help prevent a stuck sparge.

I s'pose I can do a bit more reading - I'd just read about the higher temp dissolving sugars more efficiently, and wasn't sure if anything else might be drawn out of the grains at that point or not. I made an agreement with my brain a while back that I'd swig enough beers to where it wouldn't have to deal with things like "science", but in cases like this it can backfire on me recursively.

It doesn't matter if you sparge hotter because when you mashed for an hour at the lower temperature you already converted all the sugars you wanted.

Higher temps don't bring out unfermentables, they destroy some of the enzymes that produce fermentables. After you've used the enzymes by mashing at the lower temperatures and produced the fermentables it's ok to destroy the enzymes with your hotter sparge water because you don't need them anymore.

Full conversion can often take longer at the low end of mash temps. That's generally the main concern when mashing at low temps and many mash longer than normal (say 90 minutes) to be on the safe side if they're not doing iodine tests to make sure conversion is complete.

When you mash low, the enzymes are chopping large branched starches and complex sugars into smaller, more fermentable ones. Going from a low mash temp to a higher one won't result in a less fermentable wort because the enzymes can't rebuild complex sugars from a wort full of simple ones. The inverse, however, would be true - if you let your higher mash temp slide back 5 degrees, you will have a noticeably more fermentable wort because suddenly the enzymes which break up large sugars become more active.

swankyswede said:

The inverse, however, would be true - if you let your higher mash temp slide back 5 degrees, you will have a noticeably more fermentable wort because suddenly the enzymes which break up large sugars become more active.

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You can't go backwards, above their optimum temp range the enzymes are denatured and thus inactive. Dropping the temperature would just slow the alpha-amylase production.