The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Gauging Growth Stage

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fugalh's picture
fugalh

Gauging Growth Stage

I've been reading and thinking about sourdough growth. Most instructions refer either to time or to the activity of the start. It is asserted in at least a few places that different starts may be "faster" than others though I have a hard time believing tha if one is to believe that the dominant species in those starts are L. sf and C. milleri.


It seems to be a common belief that when the start or dough has risen as high as it goes and stops rising, that the start activity has peaked. In other words, that it enters the transition to the static phase. But I wonder if this isn't an erroneous assumption. Dough, and especially the more fluid starts, are hardly airtight. I think the only thing that can be said is that an equilibrium has been reached where gas production is at least high enough to counter gravity to the extent that the gluten structure will allow it to rise.


It seems like this may even be true even early or midway through the exponential phase, or well into the death phase. Or maybe not—I'm not sure and this is my question. Does anyone know of a good way (without scientific instruments) to estimate the growth phase of sourdough? Particularly, the transition to static phase, but any indication that it's in static phase would be useful.

bwraith's picture
bwraith

There are many different organisms in various sourdough starters. L. sf and C. milleri is just one of the combinations of yeast and bacteria, but there are many others that have been identified in different cultures.


I agree that the point at which a starter stops rising is not necessarily the same as the peak of the activity, although it is probably normally a good indication of being close. Various things can affect the relationship between the rise of the dough and the actual underlying activity. If the flour has high ash content, then the acid production can go on longer before the pH drops. If the flour has strong gluten, then it can tolerate more acid before the gluten deteriorates. If you develop the gluten by stirring a firm paste, maybe it would hold more gas than if not. Hydration affects the texture and development of the gluten. So, you can have the same base culture placed into a different mixture of flour and water, same temperature, all other things equal, and probably have the peak happening at different times relative to the actual underlying peak in culture activity.


For fun, try feeding your culture with cake flour or something like "KA Italian Style" low protein flour compared to a high gluten flour. Both would have similar ash content (low) and starch content and so you might theorize they would have similar underlying rates and times for the underlying activity, but you will see one fall much sooner than the other.


One way to measure underlying activity would be to measure the acid (TTA), which I have played around with from time to time. The amount of acid produced should be well correlated with activity and is easy to measure with a pH meter and some titration equipment available in your typical high school chem lab.


Bill

Dcn Marty's picture
Dcn Marty

Peter Reinhart, in Whole Grain Breads (pg 77) discusses pH and how we measure it. He say "The typical pH range of a health starter is between 3.5 and 4.0" It would be worth checking. Litmus paper can be obtained a number of places and doesn't cost much. Try any place selling pool supplies.

LindyD's picture
LindyD

That must have been a long hike!  


I think you went on your hiking trip not long after I joined TFL.  


I have enjoyed reading your postings and it's nice to see you back.


 

fugalh's picture
fugalh

I don't doubt that some starts are more vigorous than others, though I used to. (I also used to think that the notion they would have different flavor characteristics was wildly overrated.) I was reluctantly convinced when I put it to the test in reasonably controlled home experiments. In any case there is much more than two simple strains here—there are lots of strains of yeast and bacteria both, and any given start will have many of each in different quantities.

I'm with you on the peak thing. If you thought/think of a good way to measure it I'd like to hear it. My best idea so far (lacking specialized pH or gas volume equipment) is to set up a time lapse camera and count bubbles. Not very precise, but I think you could get enough information to get an idea of where the peak is. There are several sourdough start time lapse videos on YouTube, e.g. my own http://www.youtube.com/watch?v=s5l1tvNRNas

Frequent Flyer's picture
Frequent Flyer

..the volume of my starter at a fixed ratio (1:3:3 for example) with flour and water in a graduated container.  When I plotted it (Volume of starter vs time), I got an S curve that plateaued at the end.  I want to do more of that, say at different ratios of 1:2:3, and 1:2:2.  I believe the results at that ratio (and same temperature) will be repeatable.

FF

jcking's picture
jcking

Hey Bud,

The inclusion of different room/dough temperatures would increase the usefulness of results. As would type of flour and PH. Anyone up to the task?

Jim

Frequent Flyer's picture
Frequent Flyer

I plan to do more of that.  I'd like a family of curves at different ratios so that time of rising can be predicted with some reliability.

FF 

jcking's picture
jcking

Since I've been playing around with Durum so much I'll try to quantify some results. Let's see SD hydration %, Time, Temp, PH; anything else?

Jim

Frequent Flyer's picture
Frequent Flyer

as a percentage of total flour or added flour (either one) would be good.  A curve with just a small amount of starter (say 15%) of the added flour will take much longer than one that's 33% of the added flour.

FF

jcking's picture
jcking

What would you recommend so we can keep some kind of constant?

Jim

Frequent Flyer's picture
Frequent Flyer

used extensively here with a stiff starter would make for a good standard.  The starter would be 33% of the added flour.  Each wild yeast would generate a different curve but that curve would be useful for a given temperature.

FF

 

jcking's picture
jcking

I was thinking weights, such as 25g of starter before the addition of flour and water. Or would the total volume not make any difference? I'm thinking of constants for comparison.

Jim

placebo's picture
placebo

The rate of heat transfer to and from the dough is a function of its surface area. Small amounts of dough are more easily affected by the temperature of its surroundings because of its relatively large surface area-to-volume ratio, compared to large amounts of dough.

jcking's picture
jcking

The desired volume would be when the starter peaks, No? Part of the test would be to record the starting temps of starter, flour, water and dough temps plus hydration level. Maybe throw in a PH measurement. At this point we're trying to standardise as many variables as possible, and possibly reach a DDT close to room temp. Along these lines we're hoping to graph times needed to reach the starters peak. Or somethin' like dat(?) We're still chewin' on it.

Thanks for the interest,

Jim

Edit; I may have misunderstood your volume as total volume, you're talking starting. (?)

Frequent Flyer's picture
Frequent Flyer

to start with, size of the dough is not a factor as there is no heat transfer going on.  I have a pH meter, and thermometer so I can track all that.  The previous "just for kicks" test looked like the plot below.  What's useful to me is to see similar plots at different starter to dough ratios.

jcking's picture
jcking

From my experience using Reinharts (approx 75%) starter from Artisan Breads, "the starter is ready when it has doubled in volume." Yet I don't know if it has peaked. I find if I then place it in the fridge (temp 40°F) it will continue to rise another 1/4 cup. Is this the peak? I don't know. That is what I would like to discover; what the peak is and when I should put it in the fridge. I'm putting it in the fridge to give me some time flexibility. Higher or lower hydration may have different results as may different ratios' of starter as the plot above provided by FF. Nice graph buddy, wish I could do that!

Jim

Frequent Flyer's picture
Frequent Flyer

Note that it didn't double.  I don't recall what I was doing that day.  I remember the measuring bowl I was using was very difficult to read.   I'll need something tall and thinner to use.

jcking's picture
jcking

Yet I wouldn't know how to get it on a post. {:-)) I've also been thinking about rising containers. Skinny and tall or wide and short? What would be the effect of the dough weight (downward pressure) be in a tall skinny container? Or am I just nit-picking?

Jim

placebo's picture
placebo

Sorry, I was thinking of actual bread dough, not just the starter. Nevertheless, the same physics applies. Also, it makes sense to start with the same volume of fed starter just to remove one variable that can possibly affect the results.

The room temperature here can typically fluctuate quite a bit over several hours, and I'd guess the same is true of your house. Unless your starter violates the second law of thermodynamics, there is heat moving between the starter and its surroundings so that they remain in thermal equilibrium. We all know the growth rate of a starter is affected by the ambient temperature. Smaller amounts of starter will adjust its temperature faster than a large amount will. It may turn out the effect is negligible; still, it's one thing you can try control for by starting off with a constant volume of fed starter.

jcking's picture
jcking

It seems this post is floating around a bit. Anyway I'm in Georgia and it seems to me in the tens years I've been here Spring and Fall are very short. If I ain't pushin' heat, I'm pushin' AC. So lucky for me (and the utility company) most of the year my room temp is constant. I don't expect any of these trials to be a perfect result to go by, just a closer approximation. I agree with what you say and anyone attempting to duplicate any results that come about will need to take their environment into consideration.

Jim

fugalh's picture
fugalh

Earlier this week I did a yeast experiment (not sourdough):

http://www.youtube.com/watch?v=UwtSOcaEjrI

The thing I learned is that a tall narrow container does influence the results for a stiff (bread-like) dough. Not so much for more of a slurry (I've done that before, too: http://www.youtube.com/watch?v=s5l1tvNRNas)

The big question I still have is that posited by the original post here: does the peak height correspond to the peak culture population? I very much doubt that it does. I'm guessing if you graphed height and population together the height graph would look like the population graph with the top chopped off (a la devil's tower).

I think we can measure the gas production at home, using water displacement to measure the gas produced. Take the derivative of the gas production rate and you have a good approximation of culture activity. I need to get some tubing and set up a water bath—it should make for an interesting time lapse video!

jcking's picture
jcking

I'm looking at the process as to when the yeast peaks, wild or not, it has eatin' all the available sugar and is ready to be fed. Right or wrong, I don't know, just makes sense to me. In practical use, I would probably move the starter/build to the next step before the peak. At this time I'm just trying to discover where/when the peak is.

Thanks for the container input, makes sense to me. As to gas production that's another ball of wax. Both yeast and bacteria (higher bacteria in SD) produce gas and determining which does which might need Lab Geeks (no offense Lab Geeks). Your measurements/time lapse would be interesting to me.

Please excuse FF and me if we've hijacked your thread. Very often one idea leads to another; not always in the same vain. Also hoping others gain something, if amusement only, from all our experiments. OMG are we becoming Lab Geeks (not there's anything wrong with that).

Jim

Frequent Flyer's picture
Frequent Flyer

I was one already.  :)

FF

jcking's picture
jcking

Gud fer you. Gotta go check the petri dish.

Jim

jcking's picture
jcking

Today was white SD refresh day; I did two.

#1; Temp all items 74°F, Mama 56g, water 114g, KA AP 170g ~ 2.5 hours, doubled, put in fridge - normal refresh, began with 1 cup ended with 2. Mama PH 3.9 end of double 5.1

#2; Temp all items 74°F, Mama 56g, water 114g, KA AP 170g  left to reach peak ~ 6.5 hrs, began with 1 cup peaked at 4. Mama PH 3.9 peaked PH 4.6

Jim

Frequent Flyer's picture
Frequent Flyer

2.5 hours to double at a 1:2:3 ratio is faster than my starter.  It quadrupled at it's peak?  Better check the testosterone level of your starter. :)

Good work sir!

FF

jcking's picture
jcking

Thanks Bud,

In the past I've used KA bread flour and on occasion a small portion of either whole wheat or rye. In the past I didn't attempt to control the temps. My average double took 4 to 6 hours. Recently I've switched over to KA AP only, and for this test and in the future refreshments, I'll make sure everything is at a room temp of 74°F. Constence, Constance.

The quad peak surprised me also. I'm thinking of letting the next refresh, of this Macho Mix, rise to triple. My thoughts are with the triple expansion there will be increased wild yeast activity. Also having thoughts of letting my build increase more in volume. Although I'll need to do some more thinking about the build temp to balance yeast and bacteria. More rereading is necessary.

Since I had no intention of using the Quad risen test, I let it sit over night. This morning the Quad has fallen back to about 2 1/2 cups. Humm... Seems the buggies have turned cannibalistic.

Jim

fugalh's picture
fugalh

I'm still perfecting my time lapse setup, but already I have another interesting video.

https://www.facebook.com/video/video.php?v=1720821659876

This is normal yeast inoculation vs 1/8 normal inoculation. (about 21°C at my house these days). The timestamp is hard to read (and gets covered by the video controls when you pause) but it's about 2–2.5 hours to peak (FYI I let the dough autolyse about 10 minutes before shaping and starting the film—so the dough is 15 minutes older I guess). 

The 1/8 inoculation loaf just starts really going at the end (9 hours in) but the loaf structure is shot. I wonder if there's a trick to keeping loaf structure on long rises. I have this problem a lot with slow rising yeast or sourdough loaves, even if I make what I think is a rather stiff dough. 

jcking's picture
jcking

Can't view the video; facebook wants me to log in. I refuse to be a member of any organization that would have ME as a member. Otherwise; too long of a slow rise and the enzymes take over. I'm trying to remember but I think you can counteract the enzyme breakdown with added salt or cold temps. If I can find where I read that I'll get back to you.

Jim

fugalh's picture
fugalh

Sorry, since the privacy was set to everyone I assumed it wouldn't require a login. Here it is on youtube

http://www.youtube.com/watch?v=DCU7he_nULY

It may be enzymes, partially, but I don't think it adds up. I've often made no-knead and sourdough bread that have no problem rising after a long bulk ferment on the timescale of 24 hours (or more if you include refrigeration, which doesn't slow down enzymes IIUC). I think it's the gluten getting lazy and slowly stretching.

jcking's picture
jcking

Your videos are improving.  DiMuzio says salt and lower hydration. You can boost the salt to 2.2% to slow enzyme attack. Keep testing I think a few of us are interested.

Jim

Frequent Flyer's picture
Frequent Flyer

I know I am. 

FF

jcking's picture
jcking

Higher protein/gluten can lessen the stretching. (DiMuzios' book.)

Jim