Sparging and solubility

[Velnerj]

I have read many posts on this forum about using "cold" (read room temp) water for sparging. The overwhelming anecdotal evidence seems to point to the fact that using cold water brings the same efficiency as using hot water. The only difference being is that it takes a bit longer to reach a boil afterwards.

I don't doubt my brewing brother and sister's experience. And this is not a post that disagrees with those results. But rather I would like an intermediate level science explanation of why this works.

In my mind temperature and water solubility are connected (especially with solids in liquid). The hotter the liquid (to a point) the faster and the more the solids will dissolve.

If I have a cup of cold water and add 4 table spoons of sugar to it, many of the granules will collect at the bottom even after a good amount of stirring. On the other hand, if that water is hot, the sugar dissolves very quickly and no visible granules collect at the bottom. Not only does the hot water work faster but it is able to hold more sugar than the cold water.

I figured the same would be applied to a sparge. The hot sparge water would dissolve the sugars quicker and be able to hold more sugars than cold sparge water.

But this isn't being reported. Is it that the temperature difference between room temp (25C?)and sparge water (70C?) isn't enough to make a difference? Or the amount of contact time isn't enough to make a difference? Why are the results the same regardless of sparge water temperature?

 

[RM-MN]

Have you measured the temperature of the wort collected from the sparge? The grains are hot (140-150F) and saturated with wort. The sparging mixes with this and lowers the temperature of the wort collected but not to the point of the cold water.

 

[IslandLizard]

Thank you, @Velnerj, for bringing this understated part of the process forward for discussion.

For all those reasons, I (batch) sparge with hot enough water to even call it a mashout. I then heat the collected runnings as soon as they collect, adding a gallon or so to the boil kettle at a time.

Then sparge a 2nd time with the leftover hot sparge water at whatever temp it's at.
Works well for me and the beer it yields.

 

[hotbeer]

Hotter water might make the proteins and starches swell up more and hold more. Colder water might shrink them and draw more sugars out with because of the less water they can hold.

But I don't know, I just like guessing to get the thread marked to watch.

However I did sparge at 170°F (77°C) this last week and didn't quite make the gravity of the same recipe a week before that was sparged with water more the mash temp.

I was doing a different mash/sparge though, so that probably had more bearing on why the SG was different.

 

[DBhomebrew]

to get the thread marked to watch.

No need to comment on a thread to watch it.

 

[DBhomebrew]

In addition to the grain bed heating the sparge water as mentioned above, we're not talking solid sugar crystals as described in the OP's thought experiment. The sugars are already brought into solution during the mash. The sparge merely dilutes the solution and rinses it off the grain.

 

[hotbeer]

No need to comment on a thread to watch it.

View attachment 759576

Not as much fun. If I can't venture a guess and put it out there, then the thread is not worth watching.

 

[hopjuice_71]

I have read many posts on this forum about using "cold" (read room temp) water for sparging. The overwhelming anecdotal evidence seems to point to the fact that using cold water brings the same efficiency as using hot water. The only difference being is that it takes a bit longer to reach a boil afterwards.

I don't doubt my brewing brother and sister's experience. And this is not a post that disagrees with those results. But rather I would like an intermediate level science explanation of why this works.

In my mind temperature and water solubility are connected (especially with solids in liquid). The hotter the liquid (to a point) the faster and the more the solids will dissolve.

If I have a cup of cold water and add 4 table spoons of sugar to it, many of the granules will collect at the bottom even after a good amount of stirring. On the other hand, if that water is hot, the sugar dissolves very quickly and no visible granules collect at the bottom. Not only does the hot water work faster but it is able to hold more sugar than the cold water.

I figured the same would be applied to a sparge. The hot sparge water would dissolve the sugars quicker and be able to hold more sugars than cold sparge water.

But this isn't being reported. Is it that the temperature difference between room temp (25C?)and sparge water (70C?) isn't enough to make a difference? Or the amount of contact time isn't enough to make a difference? Why are the results the same regardless of sparge water temperature?

In the example you use, the sugar starts as a solid. Its dissolution will be somewhat temperature dependent. However, when mashing and sparging, the sugar is already in solution, so this isn't an issue. Also, the amounts of glucose, maltose, maltotriose, and other oligosaccharides generated by a mash are far, far below their typical solubility limits at any temperature where water doesn't freeze. So, cold water works as well as hot water.

 

[Velnerj]

In addition to the grain bed heating the sparge water as mentioned above, we're not talking solid sugar crystals as described in the OP's thought experiment. The sugars are already brought into solution during the mash. The sparge merely dilutes the solution and rinses it off the grain.

In the example you use, the sugar starts as a solid. Its dissolution will be somewhat temperature dependent. However, when mashing and sparging, the sugar is already in solution, so this isn't an issue. Also, the amounts of glucose, maltose, maltotriose, and other oligosaccharides generated by a mash are far, far below their typical solubility limits at any temperature where water doesn't freeze. So, cold water works as well as hot water.

OK I think I get it.

For example if I want to make sweet iced tea I usually don't use solid sugar crystals. In my experience the sugar doesn't mix well and just collects in a gross pile at the bottom of the glass leaving my "sweet" tea bitter and unpleasant. Instead, I make a simple syrup, which is just a heavy dose of sugar disloved in a little bit of hot water. Once cooled I add this to my sweet tea and it mixes in just fine leaving my sweet tea uniformly sweet.

So in sparging we're not pulling sugar solids off the mash but more of a maltose syrup. Water (regardless of temp) will dilute the syrup until an equalibrium between the water and the grain is reached.

 

[doug293cz]

In the example you use, the sugar starts as a solid. Its dissolution will be somewhat temperature dependent. However, when mashing and sparging, the sugar is already in solution, so this isn't an issue. Also, the amounts of glucose, maltose, maltotriose, and other oligosaccharides generated by a mash are far, far below their typical solubility limits at any temperature where water doesn't freeze. So, cold water works as well as hot water.

This is the correct answer.

To expand on it a bit more: In order for the amylase enzymes to cut starch chains into shorter chains, and various sugars, the part of the chain being cut has to be surrounded by water (i.e. gelatinized.) So, when a sugar molecule (mono-, di-, or tri-saccharide, [i.e. glucose, maltose, maltotriose]) gets created it is surrounded by water - that is it is created in solution. The solubility of these small sugar molecules in water is very high even at low temperatures. Here is data on the solubility of maltose in water at various temperatures:

Even at room temp (21°C) the solubility limit of maltose is 44 weight %, which works out to an SG of around 1.200. The highest SG you can get in a mash with a thickness of 1.0 qt/lb is about 1.115, so there is no way that the sugar created in solution in the mash is going to precipitate to a solid.

Brew on

 

[Beermeister32]

I’m room temperature sparging / rinsing currently. I’m doing BIAB and using jug water with minerals added and a few drops lactic acid added to adjust pH and to avoid tannin extraction. I’m also de-oxygenating sparge water with some yeast and corn sugar, but that’s another story!

Warm sparge water is fine to speed up your boil a bit. Just don’t use hot water, it will extract tannins from the grain hulls. I did a hot sparge once and it destroyed the batch.

 

[Beermeister32]

It tasted very Belgian, and not in a good way!

 

[IslandLizard]

Warm sparge water is fine to speed up your boil a bit. Just don’t use hot water, it will extract tannins from the grain hulls. I did a hot sparge once and it destroyed the batch.

Difference between warm and hot water being...? Warm water is tepid, won't scald you. Hot water will?

As long as the pH of the sparge water (or better, the sparged grist) remains under 6.0 (5.8 is better) there should be no (or minimal) tannin extraction. That's essential and commonly advised. At the proper pH the temp of the sparge water (grist) is a lesser concern.

Same is true for steeping, which is why soaking/steeping grains in a kettle full of water can be a bad idea if the alkalinity of the water is high. Especially if accompanied by steeping temps over 170F.

 

[odie]

I think once the mash has completed conversion. all the sugars are already liquidized and dissolved into the mash water. All that sparging (hot or cold) is doing is rinsing out any liquid sugars that are still suspended in the grain bed