Wort stratification?

[worlddivides]

So I just took a gravity sample and it read 1.033 when it should have read 1.040 or higher. 1.032 would have been the expected gravity (based off all my batches so far, the grains, and the mash temperature, etc.) if I only mashed the grains, but I added enough table sugar that should have brought it up to around 1.040. I've had plenty of batches that were 1-4 points higher or lower than expected, but when I mashed at 149F (65C) for 80 minutes, then added a bunch of sugars to boost the OG, it seems odd. The reason I'm asking about wort stratification is because the gravity sample was crystal clear at the top but extremely dense-looking and opaque at the bottom, clearly separated into at least two distinctly different-looking layers. The only other things that were different than usual were a lower mash pH than usual (around 5.1, which should still be fine for beta-amylase activity, but I guess I added a little too much lactic acid) and a less fine crush of the grain (which I could definitely see affecting the efficiency, but it's also part of why I mashed about 20 minutes longer than I usually do). I recall see people talking about wort stratification before, but I was unable to find any real info about it, so I thought I'd ask. I expect it'll still turn out to be a tasty beer, even if the 1.033 OG the hydrometer says is accurate, but now I'm curious if this is a thing or not.

 

[kevin58]

Absolutely yes. I never take a gravity sample without first stirring thoroughly.

 

[worlddivides]

Absolutely yes. I never take a gravity sample without first stirring thoroughly.

Thanks. I have to imagine this isn't the first time this has happened to me, but this is definitely the first time it's been so noticeable (both the gravity reading itself and just how drastically different the top of the gravity sample and the bottom of the gravity sample looked). I'm already thinking of things to change going forward about this.

 

[marc1]

Sounds like you added sugar and took the sample from the fermenter?
Take one at the start of the boil and then one at the end before adding sugar. Stir well for both.

 

[mac_1103]

how drastically different the top of the gravity sample and the bottom of the gravity sample looked

So IOW, the gravity sample itself stratified? That seems like a different issue than the usual didn't stir the wort well before sampling.

 

[mabrungard]

I've experienced the same phenomena. Took a gravity sample from the wort surface in the kettle that had been sitting for several minutes after whirlpooling and the gravity was much lower than expected. Then stirred the kettle again and immediately took and sample and the result was higher and more in line with the expected gravity.

 

[worlddivides]

Sounds like you added sugar and took the sample from the fermenter?
Take one at the start of the boil and then one at the end before adding sugar. Stir well for both.

I added sugar at the very end of the boil and I did stir since I didn't want the sugar to burn the bottom of the kettle. After cooling down the wort and transferring it to the fermenter, I took the sample from the fermenter before adding any yeast. Appearance-wise, it did look very stratified, but it's kind of hard for me to imagine how table sugar dissolved and mixed into the wort could separate into a different layer from the maltose and other sugars from the mashed grains. The gravity reading I got was what I would have expected from the grains alone with no sugar added, but I added 380 grams of sugar (my recipe was for 250 grams, but I added a bit more). The reading was the biggest deviation from expected I have ever seen. I think previously the biggest difference was 5 points and I believe that was 5 points above what I expected. This was about 8 points below what I expected. I'm still a bit unsure whether the reading I read was accurate due to severely decreased efficiency in my mash due to a rougher grind (even with the additional 20 minutes) or is inaccurate because of stratification. The gravity sample tasted A LOT sweeter than usual, but I think that's also because a large percentage of the fermentables are table sugar, though it seemed bizarre for a gravity sample as low as 1.033 to taste sweeter than a gravity sample of 1.045.

 

[worlddivides]

Sounds like you added sugar and took the sample from the fermenter?
Take one at the start of the boil and then one at the end before adding sugar. Stir well for both.

In retrospect, I probably should have taken a sample from the kettle before adding the sugar. Live and learn, I guess.

 

[worlddivides]

So IOW, the gravity sample itself stratified? That seems like a different issue than the usual didn't stir the wort well before sampling.

Right. I did stir the wort pretty well, though not immediately before taking the sample.

 

[Bramling Cross]

As a fly sparger, and a brewer that uses lots of homemade invert sugar, I've certainly learned to very thoroughly stir my pre-boil entire runnings prior to taking my pre-boil entire runnings gravity and pH sample. Heavy stuff sinks, if given time.

 

[ncbrewer]

I’m really surprised that a true solution, as opposed to a suspension of solids, would stratify noticeably in the few minutes before taking a sample. Now I’ve got something else to worry about. (Not really a believer in Papazian’s DWHAHB.)

 

[worlddivides]

I’m really surprised that a true solution, as opposed to a suspension of solids, would stratify noticeably in the few minutes before taking a sample. Now I’ve got something else to worry about. (Not really a believer in Papazian’s DWHAHB.)

Since there was no way for me to know for sure, I just operated under the assumption that the hydrometer was correct. Even if it was wort stratification, I couldn't just assume that my expected gravity was the right gravity since I often go over or under the expected gravity, so I just used the one the hydrometer showed me, even though it was the biggest divergence between expected and actual gravity of any beer I've ever brewed, while also having the most table sugar added of anything I've made so far, which just made things all the more bizarre. Not sure what was going on here.

 

[BrewnWKopperKat]

I’m really surprised that a true solution, as opposed to a suspension of solids, would stratify noticeably in the few minutes before taking a sample. Now I’ve got something else to worry about. (Not really a believer in Papazian’s DWHAHB.)

and yet, perhaps, RDWHAHB applies to this topic.

There are a number of places where OG can be measured. And if the measured OG varies meaningfully from the estimate, a stir of the wort is appropriate. And, in my experiences (2.5 gal batches) a stir followed by an OG measurement always () matches the estimate.

 

[worlddivides]

and yet, perhaps, RDWHAHB applies to this topic.

There are a number of places where OG can be measured. And if the measured OG varies meaningfully from the estimate, a stir of the wort is appropriate. And, in my experiences (2.5 gal batches) a stir followed by an OG measurement always () matches the estimate.

Agreed. And this experience is the outlier that is going to affect how I handle OG readings going forward from now on.

I measured the FG yesterday and it's 1.005, which is pretty much what I expected (the estimate in Brewersfriend is 1.006).

 

[tdf]

Once upon a time I did a batch split between yeasts and I let the wort sit in the kettle post boil for a while. When I split between fermentors, the one I filled first (from a bottom port) was more than .005 gravity points higher than the second. Ever since then I've been very careful to homogenize before measuring .

 

[doug293cz]

but it's kind of hard for me to imagine how table sugar dissolved and mixed into the wort could separate into a different layer from the maltose and other sugars from the mashed grains.

Truly dissolved material will not stratify after complete homogenization. Suspended material will settle out, with the rate dependent on a lot of variables.

In retrospect, I probably should have taken a sample from the kettle before adding the sugar. Live and learn, I guess.

This is the best way to do things.

I’m really surprised that a true solution, as opposed to a suspension of solids, would stratify noticeably in the few minutes before taking a sample.

See above.

Brew on

 

[ncbrewer]

Since there was no way for me to know for sure, I just operated under the assumption that the hydrometer was correct. Even if it was wort stratification, I couldn't just assume that my expected gravity was the right gravity since I often go over or under the expected gravity, so I just used the one the hydrometer showed me, even though it was the biggest divergence between expected and actual gravity of any beer I've ever brewed, while also having the most table sugar added of anything I've made so far, which just made things all the more bizarre. Not sure what was going on here.

I agree - not a proven fact. But several posters on this thread indicate it can happen. I’m wondering if some suspended solids (e.g. cold break) in the wort are setting and causing the stratification effect. Your sample looking stratified might be an indication of this. That might even indicate that we should intentionally let the wort stand for a while before taking the sample in order to sample just the liquid, although that might be impractical. Maybe we're overthinking this.

 

[doug293cz]

That might even indicate that we should intentionally let the wort stand for a while before taking the sample in order to sample just the liquid, although that might be impractical. Maybe we're overthinking this.

I usually get my OG measurement by cold crashing the kettle dregs (after racking to the fermenter) overnight, and just sampling the clear wort. I don't need to know the OG on brew day.

Brew on

 

[tdf]

I usually get my OG measurement by cold crashing the kettle dregs (after racking to the fermenter) overnight, and just sampling the clear wort. I don't need to know the OG on brew day.

Brew on

This is a very elegant solution (pun intended) that I will definitely adopt. Thanks!

 

[worlddivides]

I agree - not a proven fact. But several posters on this thread indicate it can happen. I’m wondering if some suspended solids (e.g. cold break) in the wort are setting and causing the stratification effect. Your sample looking stratified might be an indication of this. That might even indicate that we should intentionally let the wort stand for a while before taking the sample in order to sample just the liquid, although that might be impractical. Maybe we're overthinking this.

At the time, I didn't think I'd post about it. Otherwise, I should have taken a photo. It was definitely in two visually different, distinct layers. I also didn't think about this at the time, but I probably should have stuck one of those long cooking chopsticks in there and mixed it up before taking the sample. Unfortunately, that idea didn't come to mind until after I had pitched the yeast and thrown out the gravity sample.

 

[worlddivides]

I usually get my OG measurement by cold crashing the kettle dregs (after racking to the fermenter) overnight, and just sampling the clear wort. I don't need to know the OG on brew day.

Brew on

That's a great idea, really.

 

[InspectorJon]

I usually get my OG measurement by cold crashing the kettle dregs (after racking to the fermenter) overnight, and just sampling the clear wort. I don't need to know the OG on brew day.

Brew on

This is off topic but I also refrigerate kettle dregs and end up with clear wart at as much as 50% of the Trub after a couple days. Besides possible flavor contributions, is there any reason not to use this as starter wort when diluted to appropriate gravity?

 

[doug293cz]

This is off topic but I also refrigerate kettle dregs and end up with clear wart at as much as 50% of the Trub after a couple days. Besides possible flavor contributions, is there any reason not to use this as starter wort when diluted to appropriate gravity?

I can't think of any, as long as you maintain sanitation protocols when handling the dregs/wort. Or, you could just give it a quick boil prior to making the starter. I don't bother with that, so I wouldn't use the wort for a starter myself.

Brew on

 

[doug293cz]

I usually get my OG measurement by cold crashing the kettle dregs (after racking to the fermenter) overnight, and just sampling the clear wort. I don't need to know the OG on brew day.

Brew on

This also works for FG if you do the same with fermenter dregs.

I replied to my own post to avoid the embarrassment of having someone else point out this obvious option.

Brew on

 

[sibelman]

I've experienced the same phenomena. Took a gravity sample from the wort surface in the kettle that had been sitting for several minutes after whirlpooling and the gravity was much lower than expected. Then stirred the kettle again and immediately took and sample and the result was higher and more in line with the expected gravity.

I need a chemistry lesson.

I understand that particulates would tend to settle (or, in some cases, float), but I take it that dissolved sugars also, er, sink. Maltose is highly soluble, but "... temperature and concentration, will significantly affect its actual solubility in practice."

Temperature stratification seems normal to me, but not, for example, salt. Of course, unlike salt, sugars (though hydrophyllic) aren't ions in solution, right? Is that why they behave differently? Does simple syrup stratify?

I did well in general chemistry. Organic - - not so much

 

[sibelman]

One more stratification question, focusing on the fermenter rather than the boil kettle:

When sampling from the fermenter after fermentation has slowed, should I expect the gravity (at the level of the sample port) to reflect the overall gravity of the brew (i.e., stratification has finished happening), or will a measured drop in gravity reflect additional stratification?

In other words, since I can't (and wouldn't want to) stir the beer in the fermenter, how soon will the stratification stabilize?

 

[mabrungard]

Temperature stratification seems normal to me, but not, for example, salt. Of course, unlike salt, sugars (though hydrophyllic) aren't ions in solution, right? Is that why they behave differently? Does simple syrup stratify?

With sugars, we're not dealing with ions, but relatively large molecules. In the case of a syrup, the amount of water between those individual sugar molecules is much less than what we have in a typical wort. In a syrup, the molecules are packed closely enough that they are in closer contact and may be unable to sink in the less-dense water.

The typical wort has a large amount of water between all those various sugar, trub, and other molecules. They can descend and the upper surface of the static wort may end up more watery.

In the case of fermenting beer, there is a lot of wort circulation as the CO2 production and thermal currents are in action. Fermenting beer is less likely to be stratified.

In finished beer, the yeast has consumed most of the sugars and converted them into alcohol and other soluble constituents. To some degree, anything that can't remain in the solution (beer) is likely to end up as trub at the bottom of the fermenter or container. The resulting clarified beer tends to remain mixed and non-stratified due to Brownian Motion.

 

[doug293cz]

Unlike sedimentation of particulate matter, I don't think spontaneous stratification of homogeneous solutions happens over the heights involved in brewing. I'm going to run a quick experiment where I make up a ~15°Plato/Brix (SG ~1.061) solution of sucrose (the basis for both scales. In brewing we pretend that everything soluble in wort behaves like sucrose, since maltose is too hygroscopic to make accurate measurements with.) I'll place this solution in a hydrometer cylinder, leave it undisturbed for 3 days, and then measure the Brix of a sample taken from the very top of the cylinder. If any significant stratification occurs, then the sample should have a °Brix value of less than the original ~15°Bx.

Comments on the proposed experiment are welcome.

Brew on

 

[sibelman]

Sucrose seems reasonable. The molar mass is the same as maltose.

If your test confirms our intuition, perhaps settling of particulates explains the apparent wort stratification some have observed.

 

[DuncB]

@doug293cz

A partly filled hydrometer cylinder with 1.030 and then add some sugar or syrup. Test after rest would be closer to the OP issue.
Or am I missing something?