Sourdough starter quantity predictive model

[BeanAnimal]

I have not bothered to curve fit or build out the SD table (mostly for the reasons of unpredictability that I mentioned above)

I did do it for predictable yeasts (using Craigs data as a starting point).

In the first image below - choosing 44 degrees and 9 hours, solving the 44 degree curve equation gives me 7.9% cake yeast - well outside of the charted data.

Using that number I can solve the NEW temperature equation (again 44 in this case) and in theory should return the remaining time 44 (which is 3 hours)

The second image is the proof that the return data for two stages (one of them calculated with a 7% derived lookup value) matches a single stage lookup at 44 that IS on the chart.

This all works because the commercial yeast is much more predictable - but even so, at the extremes of the chart - when hours get to 2 or less or more than maybe 150 or so - the return values are pretty meaningless.

So - again, if really want to return values for the dataset you can, you just need to use the existing data to curve fit and solve for the values that you want. The point is that those values are going to be rather meaningless when the inputs are on the extremes of the chart or close to complete fermentation to begin with.  Likewise if they input values are reasonable and small to begin with, then the chart can predict them and more often that not your lookup values will ALSO be on the chart for stage additions.

Sorry for the image sizes

[TXCraig1]

I am having trouble resolving the fermentation time based one the table.

I want to determine the fermenting times for a 35% starter.

Proof stage one at 55 degrees F for 24 hours.

Two hours remain.

Now I want to add another stage to finish the two hours.  For other yeast models, I would subtract the time and find the appropriate yeast percentage.
But for this chart, that would be significantly off the charts to yeast 65%.

How should I resolve the last two hours for another proofing stage here?

BeanAnimal's answer is correct. The chart was designed to help find a starting point for a new recipe or for converting a recipe from baker's yeast to SD. After that, experience and testing may have to take over. In the specific case you mentioned, the answer may be to raise the proofing temp up the the low 80's (typical SD yeast maximum growth rate), or there may be no answer. It's very possible there is no solution to the problem because you can only affect one of the variables (T) and there is a point where you push past the yeast's optimal temp and fermentation slows. Because you can't add more yeast, only affect the temp, not every multi-stage problem has a solution.

At the end of the day, trial and error, testing and tweaking, is a much more important tool than this chart.

[Numerator]

BeanAnimal's answer is correct. The chart was designed to help find a starting point for a new recipe or for converting a recipe from baker's yeast to SD. After that, experience and testing may have to take over. In the specific case you mentioned, the answer may be to raise the proofing temp up the the low 80's (typical SD yeast maximum growth rate), or there may be no answer. It's very possible there is no solution to the problem because you can only affect one of the variables (T) and there is a point where you push past the yeast's optimal temp and fermentation slows. Because you can't add more yeast, only affect the temp, not every multi-stage problem has a solution.

At the end of the day, trial and error, testing and tweaking, is a much more important tool than this chart.

I agree, but I needed a way to address this in the tool.  I was getting bad numbers. It turns out I was projecting so far and crossed zero hours.   I just needed to clamp to zero to get meaningful results.


This is the SD fermentation for 55 degrees and the fit curve
Chart data is blue dots, curve dots are orange


Y is hours
X is percent SD

[TXCraig1]

I don't think you were getting bad numbers; I think you were applying a bad assumption to the model - the assumption being that there was a feasible solution to the problem when there isn't.

There is also an upper limit to sd% at some point, it will dissolve your dough quickly into goop.

[SHB]

I don't think you were getting bad numbers; I think you were applying a bad assumption to the model - the assumption being that there was a feasible solution to the problem when there isn't.

There is also an upper limit to sd% at some point, it will dissolve your dough quickly into goop.

Craig,

My dough used to dissolve into goop using an even low % of starter (like 1-2% for a 24H room temp ferment. Goop. I ended up changing a bunch of things around and settled into a good rhythm but never trouble shot the old problem. I bet my RT were high (steam heated townhouse with lots of windows). Was it just plain old over fermentation or what makes it dissolve into unworkable goo?

[TXCraig1]

Some starters seem to be crazy active in making acids and enzymes, and they are simply unusable. This question gets asked a couple times every year, and the only answer is to make a new starter.

[SHB]

Interesting, I hadn't thought it was an issue with the starter but more over fermentation. I stopped doing 24 hr ferments because of it but that was a while ago. Perhaps my starter has gotten more healthy since then. Time for some experimentation. Thanks for the input.

[Heikjo]

How did the dough react? Did it expand 2-3 times and then collapse before turning into goop or did it never rise?

[SHB]

The dough rose maybe 2x but once you touched it was like a falling deck of cards.

[Heikjo]

First thing to try would be a shorter fermentation. If that doesn’t help, I’d make a new starter.

Make a dough in the evening, let it sit and just observe what happens the next day.

My old starter was very active and I only needed 2% for a 24 hour dough in 16C. Had I left it in RT, it would have become unusable. Consequently, the prediction model would never work since it would predict too much starter. The starter I got today fits the chart a lot better. Some tweaking may be neccessary, but it’s not that far off.

The chart does not work for everyone directly. Use it as a guideline or starting point, then adjust as needed.

[Pizzai-oh-no]

Simple question that I can not find the answer to when I search this topic:

When Im given a percentage of starter to use for a given fermentation, for example 20%,  is this 20% of the total flour used including what's in the starter itself or excluding it? Also is this using a 100% hydration starter or does that even matter?

[TXCraig1]

Simple question that I can not find the answer to when I search this topic:

When Im given a percentage of starter to use for a given fermentation, for example 20%,  is this 20% of the total flour used including what's in the starter itself or excluding it? Also is this using a 100% hydration starter or does that even matter?

No it wouldn't include the flour in the starter. It would be relative to the main formula flour the same as if using baker's yeast. That doesn't mean that you can necessarily ignore the flour and water in the starter however. At low % (for example, I typically use 2-3%), you can ignore it, but at higher %, it can have a meaningful impact on your dough hydration and you may need to reduce the formula water to keep the hydration where you want it.

In the chart below, you can see that at 5-6% starter (100%HR), the final dough hydration (taking the starter flour and water into account) will be about 1% higher than the formula hydration. It goes up from there. My suggestion would be to not worry about it below this line and consider adjusting the formula water above it.

[JPhillips]

Basic question --- does the % starter in this calculation refer to the total mass of the starter (flour+water) or to the mass of the flour in the starter as a percentage of total flour?

In other words, if the calculator says 10% starter, and I'm making a batch with 1000 g total flour and a 100% hydration starter, would this mean adding 100 g of starter along with 1000 g (or maybe even 950 g) flour (giving 10% starter by weight)? Or does it mean adding 200 g starter along with 900 g flour (giving 10% prefermented flour, i.e., 100 g flour in starter / 1000 g total). The former approach is used in something like Hamelman's Bread, whereas the latter approach is used in Forkish's books, but I just wanted to check since it would mean a doubling/halving of the recipe.

Thanks for the clarification!

[TXCraig1]

Say your formula was 1000g flour and the table predicted 10% starter, you'd use 100g starter in 1000g flour. You may want to adjust the formula water a bit to get the final hydration where you want it. The post two above addresses that.

[Heikjo]

If you got the right formulas, you can put in the percentages you want and the formulas will give you the correct amounts, adjusted for the contributions of the starter.