Proper Care and Feeding of Starters - Activation

[Pete-zza]

Although starters CAN be used also as preferment (depending on percentage used), their preparation scope is different and that is where your focus needs to be

Marco,

Thank you. You educated me long ago on the difference. However, some time ago when I converted Bill's use of his basic starter on a percent of water basis, I got around 26%. As a percent of total flour, I calculated around 16%. Bill prefers expressing his starter as a percent of total dough weight, in which case it is around 10%. When you have expressed your starter in the past as a percent of water, the number was 1-5%. Unless my calculations or my understanding of the matter is in error, Bill's use seems to be much closer to a preferment as used by bread bakers rather than a starter used essentially entirely for leavening purposes as you have advocated in the context of pizza dough from the very beginning. I'm sure there are many differences between commercial yeast and natural yeast starters/preferments and their preparation, but it seems to me there are still principles of maturation that are in common.

Peter

[Bill/SFNM]

I think there are two aspects you should consider in your experimentations:

- Leavening strenght
- Acidity/ Sourness

In general terms the two are inversely proportional.... For pizza you need a different balance then for bread making..

Ciao

I think it is interesting to discuss the difference between the leavening role of the starter in bread vs. pizza. In the Neapolitan pizza oven, the heat is so intense, surely the yeast are dead before they have a chance to look for the emergency exit. In the much cooler bread oven, the yeast have plenty of time to prepare their wills, get their final affairs in order, and produce a nice bounce before they succumb after a few minutes.

So if this correct, then the yeast in the starter do their job during fermentation and proofing, producing pockets of gas throughout the dough so that, if the dough is properly handled and shaped, these pockets expand in response to the intense heat to produce the wonderfully light texture of the Neapolitan pizza.

Bill/SFNM




 

[pizzanapoletana]

Marco,

 I'm sure there are many differences between commercial yeast and natural yeast starters/preferments and their preparation, but it seems to me there are still principles of maturation that are in common.

Peter

Peter,

I was aware of the percentage differences about my and Bill 's use of starters.

here  the question is how to make sure that a starters is at the right strenght and acisity balance, and the factors about poolish and other preferment, do not indicates or help to indicate this.

Ciao

[David]

I think it is interesting to discuss the difference between the leavening role of the starter in bread vs. pizza. In the Neapolitan pizza oven, the heat is so intense, surely the yeast are dead before they have a chance to look for the emergency exit. In the much cooler bread oven, the yeast have plenty of time to prepare their wills, get their final affairs in order, and produce a nice bounce before they succumb after a few minutes.
Bill/SFNM

I accept the fact that I'll never be a bread lover in this lifetime and am more than happy to offer myself to the Neapolitan putta' that I intensifies my soul.

[David]

Starter, Preferment ,Biga,Poolish,Crescito...........I'ld like another Rioja Pour favour Senior.

[Finnegans Wake]

I think it is interesting to discuss the difference between the leavening role of the starter in bread vs. pizza. In the Neapolitan pizza oven, the heat is so intense, surely the yeast are dead before they have a chance to look for the emergency exit. In the much cooler bread oven, the yeast have plenty of time to prepare their wills, get their final affairs in order, and produce a nice bounce before they succumb after a few minutes.

So if this correct, then the yeast in the starter do their job during fermentation and proofing, producing pockets of gas throughout the dough so that, if the dough is properly handled and shaped, these pockets expand in response to the intense heat to produce the wonderfully light texture of the Neapolitan pizza.

Bill/SFNM 

Great use of metaphor, Bill.  I think you'd be correct that the gas is already present in the pizza dough to give it lift: hence the lesser rise of middle where the skin has been de-gassed by pressing down or stretching out, and the greater rise along the cornicione. 

What confuses me about the yeast getting their affairs in order in the bread metaphor is this: are you positing that lower temps would have the yeast still actively producing gas as they begin to succumb to the temps, giving bread its greater rise?  Because I would think that interior temperatures would rise fairly quickly, even at 400-450F ranges, and that the rise of bread would still be 99% due to pre-existent gases.  You simply have a thicker starting dough that you've been careful in handling so that it doesn't come out a dense unrisen loaf.

Interesting stuff.

[Bill/SFNM]

What confuses me about the yeast getting their affairs in order in the bread metaphor is this: are you positing that lower temps would have the yeast still actively producing gas as they begin to succumb to the temps, giving bread its greater rise?  Because I would think that interior temperatures would rise fairly quickly, even at 400-450F ranges, and that the rise of bread would still be 99% due to pre-existent gases.  You simply have a thicker starting dough that you've been careful in handling so that it doesn't come out a dense unrisen loaf.

Interesting stuff.

It has always been my understanding (I could be wrong) that the yeast are still active for quite a while inside the bread and that they contribute greatly to the oven spring. A thermometer inserted into a baguette will show the internal temps remain for several minutes, at least, before becoming fatal (you can hear them screaming if you listen carefully and their little screams accompanied by "last-gasp" exhalations of CO2.). This is one reason for slashing the loaves and injecting steam into the oven so that the expansion is not restricted.

Bill/SFNM 

[Kinsman]

Nice analogy, I like it.

However, it's hard to believe that yeasts which die at temps much over body temp would act much differently between 550 and 850 degrees.  It's all conjecture, of course; without actually looking at the yeasts in action we can't know their precise time of death.  Or whether they felt pain, or joy.

[Kinsman]

"Just answer the question, please."

Sorry.  Anyway:

Like some others here I have observed differences in the action of the dough depending upon the state of the starter at incorporation.  Early on, I figured that mixing the dough at high Kraeusen was only natural.  All the books said to do it.  And it just seemed to make sense to me.  However, I have found that as long as the starter is viable, and has been fairly active within a week or so at room temperature, the differences in the final product are small indeed.  When we make dough we are in fact giving our starter culture a really big feeding.   Certainly if you underpitch your yeast, you will require more time for fermentation to get going. 

Like humans, the yeast seem happiest when active.  But the activity is most effective, in my observation, when the rate is stepped up incrementally.  Small feeding, larger feeding, larger feeding; all the while the yeast are reproducing.  Ideally one would take a small amount of starter culture, and step it up bit by ever-lovin' bit until you had a big wad of dough that was both the correct consistency (correct hydration level) and active as a child's mind. 

When using yeast for brewing or winemaking, it's easy to determine the proper pitching rate: you measure the specific gravity of the wort and that tells you how much food is available for the little yeasties; you want approximately one million cells per milliliter of wort per one degree Plato.  I guess if a guy wanted to figure out, for the sake of figuring out, exactly how much food were available in a given sample of flour, then he could also determine the exact number of yeast cells necessary to properly inoculate his sample, based on known nutrition requirements of the yeast. 

Just the same, two cups of 'fairly active starter' added to two pounds of flour along with salt and enough water to make a really really sticky dough works well for me. 

[Bill/SFNM]

Regarding the amount of time yeast have before their demise in the oven, here are some data I collected today while baking a rustic loaf in my conventional oven (475F - stone mode).

Amount of time in oven (min)       Temp in center
                   0                                68F
                   1                                69
                   2                                73
                   3                                82
                   4                                91
                   5                                99
                   6                               105
                   7                               110
                   8                               123

Total baking time: 20 minutes. Final temp 195F, Estimated increase in volume 200%

Bill/SFNM   

[November]

In the much cooler bread oven, the yeast have plenty of time to prepare their wills, get their final affairs in order, and produce a nice bounce before they succumb after a few minutes.

Regarding the amount of time yeast have before their demise in the oven, here are some data I collected today while baking a rustic loaf in my conventional oven (475F - stone mode). [...] Total baking time: 20 minutes. Final temp 195F, Estimated increase in volume 200%

Although this has already been covered pretty well in the past (mainly by Jeff), it bears repeating that expanding gases (and water vapor) due to heat is the primary power behind "oven spring."  This applies to bread and pizza.  I would like add in this particular situation, that it's not the "cooler" oven that's keeping the yeast alive for more than just two or three minutes at that temperature, it's the mass and shape of the bread dough.  We're talking about the difference between 1-2 cm in the thinest dimension for pizza dough (in addition to directly facing the heat), and 10-20 cm for bread.  That's an order of magnitude in difference.

Bill, what was the mass, physical dimensions, hydration, amount of yeast, and amount of rise time at what temperature for the dough you used for collecting data?  Was it a thermistor or thermocouple probe, and how far bellow the surface of the dough did you place it?  Did you have to keep opening the door to take the reading, or did you leave the probe in the dough throughout the entire baking process?

- red.november

[Bill/SFNM]

Bill, what was the mass, physical dimensions, hydration, amount of yeast, and amount of rise time at what temperature for the dough you used for collecting data?  Was it a thermistor or thermocouple probe, and how far bellow the surface of the dough did you place it?  Did you have to keep opening the door to take the reading, or did you leave the probe in the dough throughout the entire baking process?

- red.november

November,

This particular loaf was an experiment in hydration - the temperature measurements were just an afterthought. In this case, the surface area/volume ratio was similar to a thickish pizza.

Mass before baking: 1200g
Mass after baking: 906g
Diameter after baking: 29cm
Average thickness after baking: ~ 7cm
Hydration including starter: 65%
No commercial yeast
Starter amount: 15% of entire dough mass (54% flour/46%water)
8 hour room temp (68F) bulk rise + 3 day retard in refrigerator + 3 hour room temp proof in willow basket
Thermistor probe

I tried to keep the probe in the center as best as I could which necessitated adjusting it when I opened the oven to spray water (You can see the track marks of the probe (well actually the cable of the probe) in the photo below.

Other than opening the door to apply steam, the door was not otherwise opened.




 

[November]

Bill,

I would say that your steaming kept the temperature rise to a minimum.  When I first saw your data, my initial reaction was that your yeast started playing a diminishing role in oven-spring at around 7 minutes.  When I plotted your temperature data against your data adjusted for yeast productivity and vapor pressure, it was pretty clear that your yeast stopped being a major player at around 6 minutes 59 seconds.  The red "X" marked on the attached graph indicates where the temperature rise changed from logarithmic to exponential just as the yeast would have started to exhaust.

The most telling evidence of gas and water vapor expansion playing the major role is the amount of water lost.  Essentially 24.5% of the water evaporated from the dough.  You can't have that much water leave that size of a cellular structure in just 20 minutes without a great deal of pressure.  This is even more true for a pizza crust baked in less time.

In the graph: green = temperature (68-123 F), gray = yeast productivity, blue = vapor pressure.  You'll notice that the vapor pressure curve begins to fit the temperature curve exactly when the yeast begin to decline in productivity.  In the region between the green line and blue line, where the green line is on top, yeast played a contributing role since this is evidence of a thermal byproduct of yeast activity.  Everything else is physics at work.

- red.november

[Bill/SFNM]

Very interesting and cool stuff. Thanks! I learned a lot. I think I'll take more measurements with different kinds of breads.

Gas and vapor expansion is certainly going to be affected by the fact that I am at 7000 feet above sea level.

Bill/SFNM

[November]

Gas and vapor expansion is certainly going to be affected by the fact that I am at 7000 feet above sea level.

Yes, you'll have an even larger pressure gradient.

[Natural-leaven]

For those of you that use starters, what indicators do you use to determine when your starter is "optimum". Any other thoughts greatly appreciated.

Bill/SFNM

I come from mainly a bread baking background but have a lot of experience with sourdough.

I would refresh the starter a number of times before using it if it is coming from the fridge.   Coming out of storage the starter really has feeble activity.  You need robust activity and this will only come if you feed the starter a few times.  In general a starter coming out of the fridge lacks nutrients and is inhibited by fermentation byproducts. Feeding relieves this inhibition (by dilution and some neutralization of acid by flour proteins) and brings in nutrients.  If you double the volume through a few cycles of feeding every 8-12 hours you can bring it back into good shape or sooner depending on the starter and temperature.  The doubling approach is a conservative approach and the benefit is that the acidity keeps selective pressure against non desireable organisms.  Alternatively you can make a fairly aggressive dilution (say a teaspoon of starter in a cup of flour+water).  This will need less doublings but is slightly risky in that you loose the mild selective pressure against adventitious organisms that the acid provides. 

A starter degrades dough quality faster than common yeast and this is the  reason why you want a very active starter in your dough - .  This is because the acidity allows more proteolysis to occur and the gluten is attacked more aggressively than with a dough prepped with yeast alone.  The organisms are also geared to live off the flour so the window of useability is smaller than with normal yeast.  So if you begin with a moribund starter you cannot afford to let time rescue you because you dough will have degraded.
 

The criterion I use to judge if the starter is optimally active is to look for a thick layer of bubbles above the starter like what you see as the head on beer - only with larger bubbles.

[scott r]

wow, lots of great info here.

Natural Leven.  I don't know if you ever use a starter that is kept at more of a dough like consistency, but if you did how would you know when it was ready to be incorporated into your dough recipe?

Does my "wait until it has just stopped rising" method sound good?  It works for me, but I am always trying to find a better way to deal with my beloved little friends.

[Natural-leaven]

wow, lots of great info here.

Natural Leaven.  I don't know if you ever use a starter that is kept at more of a dough like consistency, but if you did how would you know when it was ready to be incorporated into your dough recipe?

Does my "wait until it has just stopped rising" method sound good?  It works for me, but I am always trying to find a better way to deal with my beloved little friends.

If you frequently refresh a stiff starter and it is actively doubling through these refreshments you can be well assured that the starter is probably in good condition for baking.  There is a caveat however.

One thing you have to keep in mind is that a volume increase is largely a function of gassing (both by yeast and lactobacilli) but the lactobacilli will provide most of the flavor.  These activities need not be synchronous so if you rely on a volume increase as a signal it actually may not fully reflect what the flavor will be like.  For example, the Sourdough International "Russian" starter or "Carl's" sourdough starter have robust leavening and peak leavening activity very early but develop flavor a lot later when leavening activity is almost dead.  Other starters are "slower" with flavor and leavening somewhat synchronized.  My feeling is this is largely controlled by the lactobacilli population - weak acid producers will not exert much inhibitory effect on the yeast and so leavening activity is robust early.  Strong acid producers, exert an inhibitory effect sooner.  So first you have to know how your culture behaves with respect to leavening and flavor and you have to use your judgment as to where your culture is on this spectrum and how and why you are using it - for leavening, for flavor or both. 

In Pizza making as seems to be done on this board IDY or fresh yeast is also being used so the starter is largely for flavor and its gassing role will be supplemented by the yeast added.  In this context it has to be realized that acidity gradually inhibits yeast activity ( even sourdough yeast, together with acceleration of decay of the gluten net alluded to before).   So the timing issue is optimizing flavor within a window of good gassing & gluten integrity that you need to determine empirically for your starter and method (hydration, temps etc. will affect the speed of all these reactions). 

For people with very hot ovens and stones, the strong push of direct bottom high heat will overcome a number of gassing limitations but if the gluten has degraded then texture will be compromised because it simply will not have the strength to hold gas leaving the liquid phase on exposure to high heat.

Lastly, in terms of time people should realize that even with a small inoculum the process is exponential and so dough quality can degrade quite fast.  For example if you put 5% starter and assume a 6-8 hour doubling time for an active starter then in 6-8 hours you are at the equivalent of having added 10% in 12-16 hours 20% etc.  Of course temperature and activity of the starter etc. influence this but I just want to draw attention to the fact that a small inoculum becomes a large fraction of the dough very quickly and so the time window of optimum activity & dough quality can run away from you quite fast. 

[Kinsman]

One of the reasons I adopted a room-temp environment for my cultures is because of the lag between refrigeration and working temp.  Since the cultures seemed to be happiest at room temp, I began leaving them there all the time.  Also, observation of their habits is easier (for me anyhow).  The dough (I make bread and pizza) develops excellent structure and flavors within a half day or so of fermentation and that's where I like to capture it...while the thing is really active.  If I wait and bake the dough much after high kraeusen, both structure and flavors suffer greatly.

It's my impression that yeast activity during the primary phases of fermentation develops the gluten and therefore is primarily responsible for structure (and flavors) within the dough and that moisture escaping as steam is much more responsible for oven spring. Concur?

[November]

Chris,

I agree that the cell movement in the dough caused by the fermentation process aids gluten development, although not as much as the kneading itself.  Gas and water vapor expansion is definitely the primary cause of oven spring.

- red.november