Batch sparge temperature

[droder1]

So random question I got to thinking about when brewing this evening. For all sparging, it is common the goal is a grain bed and resulting runnings of about 170 (give or take); to avoid tannins at any higher of a temp and shut down enzymes/ max viscosity. So when fly sparging, you use 170 or so (maybe a bit higher) water and it rises after a bit of time to just about 170. Commercial breweries the same thing.

However for batch sparging, I see it often recommended to come in maybe 180-185 to raise the grain bed to 170. If you batch sparge in at 170 I to a 155 saach rest it will end up around 160, certainly not 170.

So my question, when starting with 185 water; inevitably some of the grains are going to get hit with this 'over hot' water for at least a minute or two before things equalize and the overall temp drops and stabilizes. What is the view on tannins or other undesirables? So quick and minor not a worry?


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[Gnomebrewer]

Boiling water is often added for infusion.....no tannin extraction.
Also, grains are boiled in decoction mashing....again, no tannin extraction.
Why? I believe that it's more to do with the mash pH. As long as your pH stays low enough, the higher temperatures shouldn't hurt. Decoctions are taken with the thick part of the grist which helps keep the pH down when it's boiled. Adding your sparge water a bit hotter shouldn't give time for a significant pH increase in that small area.

 

[RM-MN]

Yes, Gnomebrewer has it right, tannin extraction is driven mostly by pH being too high. Your grain bed/wort should be plenty low in pH to prevent that from happening for the first batch sparge. If you continue to sparge over and over you can bring the pH up enough to be a problem.

To completely avoid the chance of tannin extraction, use cold water for your batch sparge. The point of a mash out is to stop the enzyme action. By raising the temperature to 170, you denature the enzymes. This really isn't necessary for a batch sparge since you aren't going to keep the grain bed wet for long, just add the water, stir, and drain it.

On the other side of the equation, the enzymes that convert the starches have a very narrow temperature range to make them work so add cold water for your sparge and you quickly cool the grain bed so the enzymes will stop working anyway and now you have zero chance of extracting tannins. Experiments with this cold water sparge have shown that there is little difference in efficiency.