The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Maintaining a starter

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bobku's picture
bobku

Maintaining a starter

I have been baking sourdough bread for a couple of months now almost every weekend. I don't understand why we keep more starter than we need. Constantly discarding some or finding other thing to bake with it. Why can't a small amount of starter be kept in the refrigerator than taken out a few days before baking, building to amount you need to bake with plus slightly more. Put the same small amount of fresh starter back in the refrigerator for next week. Don't know if I am missing something does anyone know why this might not be a good idea, will I be losing some flavor by not keeping a mother starter. From everything I've read your starter should be as fresh as possible.

GermanFoodie's picture
GermanFoodie

with a fresh starter, that is, one that was fed the day prior. That said, I am assuming you know exactly how much starter you need for what recipe. Just plug all of that into an Excel spreadsheet and it will compute for you how much starter you have to have in order to bake a particular bread.

That's how we used to do it when we still had our bakery, in order to minimize food waste. Makes sense?

loydb's picture
loydb

That's pretty much what I do. If I end up erring and have too much, so far I've done sourdough biscuits, pancakes and crackers with extra. I keep between 8-9 oz of starter. The day before I make the dough (and usually two days before I plan on baking), I turn 3 oz into the batch that goes back into the fridge, and the remaining 6 oz into anywhere from 14-18 oz of preferment, depending on the hydration I'm shooting for. It sits on the counter all day, then retards overnight in the fridge. The next morning, it warms up for a couple of hours and then I make the dough, which also sits out all day, and retards overnight. The following morning, it warms up, gets shaped, and proofs. Then bake early or mid-afternoon.

The nice thing about this is that at any point up until the dough is shaped, you can extend the refrigeration period for a few days if something comes up.

But yeah, I consider throwing out more than a tablespoon of starter to be a crime, or at the very least a sign of moral turpitude :)

 

thomaschacon's picture
thomaschacon (not verified)

Sometimes I'll take a bit of starter out of the starter jar and build it up to whatever I need for the loaves I plan to bake.

Sometimes I'll build it up the whole jar, remembering to reserve some for its continuance.

Sometimes–more often than I care to admit–I forget to reserve a bit and rush to the kitchen, hoping to find a spoon with some residual goo, hoping it's enough to rebuild.

Sometimes there isn't enough and I have to rebuild from scratch (which I'm having to do now). Grrr! No sourdough until Nov 4! How am I going to survive?!

I guess I don't think of there being a demarcation between "mother starter" and the starter I build for a loaf.

It's all the same thing to me.

Maverick's picture
Maverick

It depends on the age of the starter. That schedule is fine as long as it is not a new starter. Otherwise I think you lose stability. To answer the other part of the question about flavor, I do believe that the inhabitants of a starter kept at room temperature will normally be different than that of one kept in the refrigerator. I can't say this will translate into different flavoring in every bread, but it might. If you don't bake often enough and don't want to "discard" any starter, then by all means keep a small amount in the refigerator to build on later. Another thing I have seen people do is keep a larger amount in the refrigerator and just take out a small amount to build on each time they make bread. When it gets low enough they build the refrigerator one up again. I have never done that myself, but it just shows there are several options out there.

Doc.Dough's picture
Doc.Dough

At a reasonably cold refrigerator temperature of 36°F, a starter that has been refreshed in a ratio of 1:4:4 and let sit for one hour to allow it to start growning before refrigeration will mature the LAB (i.e., the pH drops to 3.8 or below) in about 5 days but will grow almost no yeast after it has been in the refrigerator for a couple of hours because it is too cold.  Thus if you think that you have a "mother" that is dormant you are in trouble.  After a week you need at least two and probably 4 refresh cycles before the populations of LAB and yeast are again stable and in the ratio of approximately 100:1 [LAB:yeast].  This also is dependent on refreshing at fairly high ratios (1:4:4 to 1:20:20) so that the post-refresh pH is above 4.8 and preferably above 5.3.  Even maintaining a starter at room temperature imposes constraints on the refresh ratio and refresh timing. In the summer when room temperatures can climb above 25°C/77°F, the growth rates are high enough to demand three or four refresh cycles per 24 hr day if the refresh ratio is 1:1:1 just to avoid acid building up to the point where post refresh pH is less than 4.3 below which the growth rate of the LAB is less than that of the yeast.  A long series of extended refresh cycles at high temperature and low ratios (1:1:1) will acidify the starter sufficiently to suppress the LAB population relative to the yeast.

Maverick's picture
Maverick

Quote:
Even maintaining a starter at room temperature imposes constraints on the refresh ratio and refresh timing. In the summer when room temperatures can climb above 25°C/77°F, the growth rates are high enough to demand three or four refresh cycles per 24 hr day if the refresh ratio is 1:1:1 just to avoid acid building up to the point where post refresh pH is less than 4.3 below which the growth rate of the LAB is less than that of the yeast.  A long series of extended refresh cycles at high temperature and low ratios (1:1:1) will acidify the starter sufficiently to suppress the LAB population relative to the yeast.

Wouldn't giving a larger feeding in proportion to the amount of starter during these warmer times be the equivelent? Or are you saying even with more flour to fuel the yeast and water to dilute the by-products, that the warmer temperatures will throw things out of whack unless refreshed more often? Now I am curious.

Doc.Dough's picture
Doc.Dough

Increasing refreshment ratios (1:4:4 to 1:20:20) is an effective strategy in warm environments (whether induced by weather, climate, or the thermostat on the wall). Just remember that doubling the refresh ratio just delays ripening by one generation time, so at a temperature of 25°C changing the refresh ratio from 1:4:4 to 1:8:8 provides you an extra 3 hrs (from a little over 7.5 hrs for an 8X increase to a little more than 10 hrs for a 16X increase based on the yeast growth rates - the LAB will have stopped growing well before this since they shut down based on pH and grow faster than the yeast at all temperatures). Thus if you want to feed twice a day at 25°C, you need to refresh at something like 1:13:13.  But when it is cool (15°C) 2:5:5 and one feeding a day is adequate. You can use the model below to set up an Excel spreadsheet that will calculate species populations as a function of time and temperature which you will need to validate and perhaps adjust for your own particular starter.  Just remember that the LAB grows faster than yeast at all temperatures and while it stops replicating at a pH of 3.8 it continues to produce acid down to pH 3.5 (or so), while yeast stops growing when it consumes the available nutrients in the mix.  The growth rates of the LAB and yeast are approximately the same at a pH of 4.3 so it is important to refresh at a high enough ratio to achieve a post-refresh pH that is greater than 4.4-4.5 to maintain the LAB:yeast ratio.  You can slow things down in the summer by adding a LITTLE salt but you will have to run that experiment on your own.

The table below reproduces the generation times for two species of LAB and a common yeast found in sourdough starters.  The units are [doublings per hour] and are based on the following lab-validated growth model developed by Michael Ganzle.

Model form:

Growth rate =  a * (K-t)^b * exp[c*(K-T)] = ln(2)/generation time

Generation time = ln(2)/{ a * (K-T)^b * exp[c*(K-T)] }

K=41 for LAB, K=36 for yeast; T = temperature  in °C

Species population N=N0 * 2^{t / [ a * (K-T)^b * exp(c*(K-T)) ] }

where t is time in hours

a, b, & c derived by curve fitting lab data to parametric model

  L. SF I  L. SF II  Yeast (C-Milleri)

a  0.1267  0.0682  0.0124

b  1.5404  1.9782  2.981

c  -0.1931  -0.2233  -0.3355

T(°F)   T (°C)L. SF IL.  SF IIYeast (C-Milleri)
35.620.0190.0160.004
39.240.0260.0220.008
42.860.0350.0310.013
46.480.0470.0430.021
50.0100.0630.060.033
53.6120.0840.080.052
57.2140.110.110.078
60.8160.140.150.11
64.4180.190.20.16
68.0200.240.260.23
71.6220.30.290.3
75.2240.370.370.37
78.8260.450.460.42
82.4280.490.550.42
86.0300.610.640.35
89.6320.660.70.2
93.2340.660.70.05
96.8360.580.540
100.4380.390.31 
104.0400.10.055 
105.84100 
Doc.Dough's picture
Doc.Dough

Your understanding of the process and the rationale is phenomenally good.

Just follow your inclinations and you will be fine.