The Fresh Loaf

A Community of Amateur Bakers and Artisan Bread Enthusiasts.

Why does SD Bread get more sour with time?

DanAyo's picture
DanAyo

Why does SD Bread get more sour with time?

  1. Why does SD Bread get more sour with time?

There is a noticeable increase in sour flavor if the bread is allowed to rest for 24hr or so. Does anyone have an explanation?

  1. The sour flavor is enhance by waiting 24hr to slice
  2. The sour flavor also changes characteristics (flavor profile) after freezing. It seems to pick up a sharper (acetic?) flavor.
  3. If a frozen slice is allowed to sit out on the cabinet a few hours, the flavor is almost too sour, even for a “sour head” like me.

By the way, this may make a difference. The breads I bake favor Lactic Acids. The great majority of the sour flavor is derived from warm (77-78F) and long (16-17.5 hr) ferments. Cold fermentation is only used for convenience and not intended for flavor.  Although some acetic acids are noticeable after an overnight retard @39F.

I have baked and eaten a truckload of SD over the years and the observations above are a result of that history.

gerhard's picture
gerhard

but in my little mind I thought that as the bread's moisture is reduced the percentage of acid increases 🤷🏼‍♂️

DanAyo's picture
DanAyo

Gerhard, your idea makes more sense than anything I’ve come up with so far. It a may be true, but maybe not.

GaryBishop's picture
GaryBishop

Mine has a perfect level of sour on the first day and seems to become more bland over time. I had thought about posting a question about the volatility of the sour components. 

headupinclouds's picture
headupinclouds

I'm curious about this as well.  I've noticed on several occasions that my pre-bake pH dough measurement (admittedly not TTA) is lower than my post-bake next-day bread slice pH measurement.  My measurement process is very casual (I could be wrong), but I've observed it enough that it seems repeatable.  It seems plausible, but I would be curious to hear from others on this, as it could impact my final proof pH cutoff for a given target final bread pH (e.g., if I want a bread pH of 4.2 I should aim for a dough pH of 4.2 - X).  I typically don't measure immediately post-bake so I'm not sure how much of this happens due to baking phenomena or from the longer-term overnight cooling.

DanAyo's picture
DanAyo

HeadUp, I measured the dough and also the baked crumb in the last week or so. Thought it might interest you.

It appears the PH of the crumb is only slightly different from the dough.“ The mature levain was PH 3.72 and the dough on the right that used the young levain was 3.70.”Crumb was PH 3.375 and 3.71 respectively.” The baked bread crumb had only a very slight increase in pH for both loaves. 

A brief history of the test

A comparison test was conducted comparing a mature levain (3.75X rise) to a young levain (0.50X rise) The image below shows the two doughs after BF. The taller of the two used the mature levain. I concluded (without measuring TTA) that even though the pH were similar for both loaves, that the degraded dough was a results of much higher TTA. The excess acids harmed the gluten. I am not scientific, but these are my thoughts after close observation. Below are the loaves produced. The degradated gluten resulted from the mature levain. The degraded dough was more sour tasting, but both loaves produced a very sour flavor.K
headupinclouds's picture
headupinclouds

I am interested, as I have been trying to learn more about fermentation by tracking pH in my bakes.  I'm a little unclear on this line:

The mature levain was PH 3.72 and the dough on the right that used the young levain was 3.70.”Crumb was PH 3.375 and 3.71 respectively.

Am I correct in reading that as "the final dough from the mature levain was pH 3.72 ..."?  So the before/after is 3.72/3.375 and 3.70/3.71?

Here is what I observed in my most recent desem bake with Rouge de Bourdeaux and a new starter: build 1= 4.39 (60 F @ 60%), build 2 = 4.53 (60 F @ 60%), BF=4.46 (~30%), FP=4.15 (close to 2x although I am using a 95F proof and don't trust the aliquot due to temperature changes), and a next day crumb of 4.28.  This is similar to what I've observed in previous bakes.  I'll try to measure more rigorously next time to confirm this.

This seems to be quite different than what you observe, although it is whole grain at a much higher target pH.  Perhaps bran is playing a role?  I do have a few experiences that corroborate this measurement with a perceived reduction in sour taste, although I usually don't eat soon after baker.

Caveat: I'm just taking single measurements in one location.  Multiple measurements in different locations would provide a better picture.  (I plan to watch the video you posted soon for tips.)

BTW, I purchased the Milwaukee spear tip model directly from the supplier based on your writeup.

Ilya Flyamer's picture
Ilya Flyamer

You can't measure the pH by just sticking the probe into the crumb, it's measuring a lot of air too this way. You probably should dissolve a piece of bread in some distilled water for an accurate measurement.

DanAyo's picture
DanAyo

Ilya. Jason the tech guy from Milwaukee Instrument tells me that crumb readings can be taken by placing the spear tip (food type) probe directly into the crumb. The bread was sliced ~24 hours after the bake. Doesn’t the close measurements seem to bear this out?

Ilya Flyamer's picture
Ilya Flyamer

Perhaps I'm wrong, maybe the "food type" probe is tolerant to this kind of issue? Otherwise it sounds just like a mistake of incomplete probe submersion with regular probes...

headupinclouds's picture
headupinclouds

Thanks for the note.  I try to compress the crumb with the spear tip when I take the measurement.  Next time I can try a few different measurement approaches to check for consensus and will try your method when I am able to pick up some distilled water.

Ilya Flyamer's picture
Ilya Flyamer

Regular water should be fine too, really, if you don't have distilled water.

headupinclouds's picture
headupinclouds
 open crumbcompressed/rolled crumbdissolved crumb 100% hydrationdissolved crumb 200% hydrationopen crumb (again)10 g 4.01 pH solution10 g 4.01 pH solution + 20 g H20
14.654.674.674.714.614.024.03
24.64.674.674.714.633.994.03
34.634.634.664.714.633.964.03
44.624.634.674.714.633.964.03
54.614.654.664.714.633.964.05
64.644.624.674.714.633.954.06
74.714.644.674.714.673.954.07
84.674.654.674.714.663.944.06
94.644.614.674.714.653.954.06
104.674.674.674.714.653.954.05
mean4.6444.6444.6684.714.6393.9634.047
std0.0327280.0217050.00421600.017920.024060.01567

This was a very quick experiment to compare a few methods of measuring the pH of a piece of bread.  I took 10 consecutive readings for the following categories:

  • open crumb: placed the probe into a slice of bread with a best-effort attempt to compress the crumb (note that the location was sampled randomly across the slice of bread, and repeated locations at the same location would probably reduce variance but make the mean less comparable to the dissolved crumb mean, which is expected to be more uniform (the probe was not rinsed or cleaned between readings)
  • compressed crumb ball: removed the crust and rolled the crumb into a ball (the probe was not rinsed or cleaned between readings)
  • dissolved crumb @ 100% hydration: dissolved the dough ball by hand in 100% (remineralized) RO H20 by weight to the consistency of soupy porridge (the probe was rinsed in running tap and then RO water (the meter wouldn't otherwise reset due to residue on the spear tip)) -- using a blender might be better
  • dissolved crumb @ 200% hydration: dissolved the dough ball by hand in 100% (remineralized) RO H20 by weight to the consistency of very soupy porridge (the probe was rinsed in running tap and then RO water (the meter wouldn't otherwise reset due to residue on the spear tip))
  • open crumb again: repeated the open crumb slice measurements on a small portion of the slice to check for drift (this was a smaller piece of bread and the measurement location will have less spatial variance)

Follow-ups: Misted slice measurement; calibrate and compare the spear tip probe with the wet probe; repeat with distilled H20; use a blender for more uniform consistency in dissolved crumb tests

UPDATE: Added columns for 10 g 4.01 calibration solution and the same solution diluted in 20 g of remineralized RO water.  Diluting the solution with 200% water by weight increased the pH by 0.084.  I calibrated immediately before measurements in these last columns, so I was a little surprised that the mean was 3.963 (if anything I would expect slight contamination to increase this).  I'm sure my process can be improved.  My hunch is that with distilled water the hydrated crumb measurement will match the dry crumb measurement but with reduced variance.

DanAyo's picture
DanAyo

Thanks for posting this. Once followup question and details are finalized I like to add it to the pH and pH Meter post for others to take advantage of.

Please explain this, “ Follow-ups: Misted slice measurement; calibrate and compare the spear tip probe with the wet probe; repeat with distilled H20; use a blender for more uniform consistency in dissolved crumb tests”

Where is the spear tip and wet (bulb probe) probe used in the sheet?

So the 200% hydration was spot on. I understand that to be 50g of bread crumb and 100g of distilled water. Is this correct?

Comparing the 100 and 200% hydration, are we to believe that the water had an affect on the pH reading, even though the variance n the 100% was slight the readings were almost equally distanced between the 2 columns.

headupinclouds's picture
headupinclouds

I didn't use the bulb probe in any of those measurements but thought that it would be an interesting data point.  The 200% hydration measurement did have the least variance.  That isn't too surprising since I would expect the dry crumb measurements to be more spatially variant from non-uniformity in mixing and fermentation (I changed the location each time hoping to get a more meaningful average), and the more homogeneous texture of the 200% hydration measurements would seem to provide a more consistent interface for measurements, although I have no expertise in this realm.

> Comparing the 100 and 200% hydration, are we to believe that the water had an effect on the pH reading,

Increasing hydration does seem to increase the pH, by 0.024 in the case of 100% and 0.066 in the case of 200% hydration.   I could try measuring various dilutions of the known calibration solution using the same remineralized RO water to see if it is similarly affected, and could also repeat this with some distilled water as Ilya initially suggested to better understand this.  I'll try to take a look later today.

DanAyo's picture
DanAyo

I get the consistent reading in the diluted samples. It does appear the probe and meter are very accurate, though.

Keep up the great work, many of us can benefit by your trials.

HeiHei29er's picture
HeiHei29er

Call me old school, but I agree with you Ilya.  I would be much more comfortable taking 10g of dough and dissolve it in about 50-100g of distilled water.  Then, I’d take 10g of crumb and dissolve it in the same volume of distilled water.  I think that’s the only way I would be comfortable with an apples-to-apples comparison.

DanAyo's picture
DanAyo

HeadUp, “ Am I correct in reading that as "the final dough from the mature levain was pH 3.72 ..."?  So the before/after is 3.72/3.375 and 3.70/3.71?”

Yes.

Doc.Dough's picture
Doc.Dough

It occurs to me that while water does not evaporate from the cooled bread (other than to dry it out which is not what we are observing), the crystalization of the starch does tie up water and might act to concentrate the acidity and thus impact flavor.

The one-time reversibility of this by re-gelatinizing the starch might give you a way to test that hypothesis.  Allow one slice to thaw on the counter and microwave one to >140°F and taste them side by side.

I have seen it in the past (once, maybe 15 yers ago) but it was not repeatable so I stopped searching for it.  But now it is back, and it is not subtle at all. I certainly was not asking myself "is this really more sour than it was yesterday?" - more a matter of WOW! THIS IS REALLY A LOT MORE SOUR THAN YESTERDAY!

DanAyo's picture
DanAyo

Doc, I can confirm that in my case the slice that is microwaved right out of the freezer is not nearly as sour as the slice that is removed from the freezer and left out on the counter to defrost. This is not to say that the microwaved slice is not sour, just that is not nearly as sour as the defrosted slice.  I had both this morning and have also seen it consistently in the past. I love sour and the slice that is left out on the counter is almost too sour.

Doc, do you think this is related to Lactic sour more so than Acetic?
I know you recently started baking Lactic SD.

Doc.Dough's picture
Doc.Dough

That is good to know.  I have not had time to run that experiment but it is on my list for later today.

I don't think it is attributable to one type of acid or another (yet) though if we are clever we may figure out a way to tease that out of some yet TBD experiment. 

If sour flavor directly reflects TTA (as is the claim and it agrees with my observation) then both acids contribute their share to the result.  The difference between the thawed on the counter and thawed in the microwave is the starch.  If you save a piece of the microwaved bread and let it cool down and the starch re-crystalizes then if that is the mechanism it may get more sour.

DanAyo's picture
DanAyo

Doc, I ran your test.

Removed 1 slice of frozen SFSD from freezer. 
Cut that slice in half
Placed 1 half on the counter and put other half back in freezer
Once the counter slice thawed completely, the half in the freezer was microwaved.

Both test halves were tasted a total of 3 times during the comparison.

There was no difference what so ever in the sour taste or any other taste.

The microwaved slice was also allowed to cool and a comparison was made with no distinguishable taste.

I think we can rule this one out.