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Sourdough Rise Time Modelling and Recipe Calculators

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bwraith's picture
bwraith

Sourdough Rise Time Modelling and Recipe Calculators

I've posted a spreadsheet that summarizes what I do these days to analyze rise times and to dissect recipes or design my own variations. Below is some discussion and also some instructions for the spreadsheet. Use it as is, and modify it as you like. It may contain errors, bugs, and it is not carefully designed to work on all computers and operating systems. It uses "macros", which you have to enable, and it probably will only work with relatively recent versions of Excel that would be available in Microsoft Office 2003 or later. I notice that I can use the spreadsheet on a Macbook with Microsoft Office 2004 for Mac installed on it.

I've built some models of fermentation rates and rise times over the last few years. There is no science here, just trial and error in an attempt to engineer an admittedly crude but hopefully useful model based partly on observations and partly on what little I can gather from some scientific papers and a few baking books. You can beat me up if you want with general treatises on all the ways this doesn't make sense or can't possibly work or is theoretically completely incorrect. I already am well aware I'm skating on thin ice (or possibly am in a coma under the ice already) in any sort of rigorous intellectual or scientific sense. However, if you want to make some specific constructive suggestions or point out neat ways to get a good handle on this or that factor or places where you think the model gives wrong answers and what should be the right answer, that would be interesting.

I thought it might be worth tossing out this basic approach for how to get a handle on rise times vs. inoculation, salt, temperature, or other factors. I also did some tests on low and high hydration doughs, but I'm not describing that in the simpler approach below.

I went down some fairly lengthy testing roads and built a whole somewhat extensive spreadsheet to model rise time and fermentation time with a few more factors than indicated below in it, but a simpler, and fairly practical approach would be something like:

First make sure your starter is fully vibrant and well refreshed, and make enough to go into these test doughs.

Make up 4 small doughs using a "typical blend" of flour you might most often use. You can guess adjustments for different flours, but it's nice to do this with the flour you will tend to be using most. Make the doughs with about 200g of total flour each as follows. Use 75% hydration, which will make somewhat wet easily worked doughs. In two of the doughs, use 4% inoculation (fermented flour as a percent of total flour), one with no salt, one with 2% salt. In the other two, use 16% inoculation, one with no salt, one with 2% salt.

Try to work all the doughs exactly the same way and for the same amount of time, so the gluten development is about the same. Set them to rise in containers that allow you to determine the time it takes them to double in volume. Remember to carefully label them with the initial time and the volume level they had initially.

When they double in volume note the time, shape them into little loaves and monitor them to see when they proof. Note that time also for each dough. Bake each one when it is ready all using the same temperature if possible.

You can then use the times you get for doubling and proofing of these test doughs when you make other recipes. The total mix to bake time should be the same, whether you shape much earlier or shape closer to when the dough has doubled. Also, the fermentation times should be the same (adjusted for inoculation and salt) for other recipes, regardless of whether you deflate the dough during "folds" or do other handling techniques that may make it difficult to tell when a dough has really risen.

The difference in time to double the volume for an inoculation of 4% vs. 16% will give you an idea of how much time 2 doublings of the population of your starter takes at the temperature you used. The rise times should be roughly logarithmic with respect to inoculation, since bacterial population growth is roughly exponential during most of the bulk fermentation. An inoculation of 8% should take 1/2 of that difference in time less time to rise than the 4% inoculation and 1/2 of that difference more time to rise than the 16% inoculation. You should notice that the salted ones ferment more slowly, so you can adjust for salted vs. unsalted with the information from your test doughs. Unsalted is useful for knowing how long a levain should ripen.

Note that I don't include a 32% inoculation, which maybe should take one generation time less than the 16% inoculation. It seems to me that it doesn't work that way because 32% inoculation with a ripe levain leads to early gluten deterioration or maybe early slowing of the fermentation rate, so a dough rises more slowly than you would think, given the large inoculation. In the model I built, adjustments are made to try to account for slower rises at higher inoculations.

Adjusting for temperature is not so easy, since it gets crazy if you try to run all kinds of tests at different temperatures. I just use the models in a Ganzle paper I have that describe the growth rate as a function of temperature for L. sf and C. milleri. You can adjust the rise times to reflect the relative activity rate at a different temperature from the one you used in your tests. The time should just be inversely proportional to the growth rate.

Finally, as you start to play with more and different test doughs, you'll notice that sometimes rise times don't seem to make sense, and usually I've narrowed it down to differences in gluten quality for different doughs. For example, I've made little test doughs at very low hydration with salt. The gluten becomes incredibly stiff in a small test dough, and it just won't rise. You know the fermentation has to be ongoing, yet the volume increase is not there.

Now, what I actually did was a lot more test doughs than the ones above. I made some rough assumptions, like that the growth rate in doughs is exponential during most of the bulk fermentation, and that the dough is doubled and then proofed when the organisms reach a certain population concentration relative to the initial population concentration in a ripe starter. I'm also assuming that factors such as salt and hydration have a simple multiplicative effect on the growth rate and that the relative growth rates follow the temperature curves in a paper by Ganzle about modelling sourdough organism growth rates. The last thing I did was try to make a model of "gluten quality", which is a function of salt, inoculation percentage, and hydration. The idea is that a very stiff or very loose dough will rise less than a dough somewhere in the middle. All of this is summarized in a spreadsheet I built that tries to set all the model parameters in such a way as to minimize the difference in rise time estimates of model vs. experiment on a large number of different test doughs.

OK, it's a little crazy, I am the first to admit. However, I've found myself doing better breads and able to design my own recipes with it, since I'm not tied to just the observed condition of the dough itself, which may vary a great deal from one recipe to another and is hard for one baker to describe to another. Instead, I have a pretty good idea how long the fermentation should take for my starter, my temperatures, and the recipe inoculations, salt, and hydrations, so I can ferment and proof more according to "the clock". It doesn't mean I don't adjust according to feel and observation of the dough itself, but it seems to help a great deal to have the model's estimates of the right times in mind as I do that, in case there is something misleading about the observations or the feel of a new recipe.

The spreadsheet I'm including has blue cells that are the inputs. There are graphs of various functions used to generate the adjustments to the growth rates of the organisms in the culture. The main inputs are the inoculation, which is the percentage of flour that is coming from a preferment in the total flour in the dough. So if there is a levain with 100g of flour and 100g of water, and the total flour in the dough is 1Kg (900g of additional flour), then the inoculation would be 10%. The salt and hydration are percentages of the total flour in the dough. So, in the example above, if the levain has 100g of flour and 100g of water, and you add 900g of flour to the levain along with 600g of water and 20g of salt, the salt is 2% and the hydration of the dough is 70% (100g water in levain + 600g water added to the dough = 700g in 1Kg of total flour in the dough is 70%).

The "bread calc" tab on the spreadsheet is a general hearth bread recipe that can be changed to match many different hearth breads. You can use it to duplicate a recipe in a book to understand the rise times and see the percentages of ingredients in a consistent format. You can also use it to design your own recipes or make small changes such as scaling the recipe to a different amount, adjusting the amounts of preferment, types of flours, hydration, and so on, to suit your needs.

Instructions

Here's some stuff to help figure out how to use the spreadsheet for calculating rise times and hearth bread recipes. If you read this step by step, it should help a lot. However, I admit it's long and may take a while to get through. Sorry, I don't know an easy way around it.

First of all, you have to "enable macros", so that the software I wrote will run inside excel. You do that by going to "Tools", then opening the  "Macro" dragdown menu, then "Security..." , and finally set the "security level" to "medium". You then have to close Excel and open it again. When you do open the Excel file, it will bring up a dialog box that asks you to decide whether to "enable macros" or not. You should click on the button labeled "Enable Macros".

Once that is done, the file should open for you, and you probably will see the "summary page". There are 4 pages: 1) Summary Page, 2) Bread Calc, 3) Graphs, 4) Model. To change pages you click on the tabs at the bottom of the window. The only pages that you really need to understand are the Summary Page and the Bread Calc page.

Remember that the numbers you can change are highlighted in blue, other than the labels for ingredients and flours in the bread calc page, which can be changed, too. Look for the comments that pop up when you run your mouse over the text boxes with red triangles in them. Those comments should help a lot to figure out what is going on in the spreadsheets.

The Bread Calc page has a generic bread recipe on it. You can change the amounts you see in blue. Most of the amounts you enter are bakers' percentages. If you type 31% (literally a 3, a 1, and a shift-5 for % sign), it will take that as "31%". Some of the amounts are in grams. In that case, just type in the number, like to enter 12g type 12 (literally a 1, then a 2) in the field for the weight in grams that should be highlighted in blue. An example of that is the amount of storage starter.

On the Bread Calc page, you can set up a recipe by first setting the overall numbers down below: the total flour, the overall hydration percentage, the salt percentage, and the desired inoculation percentage (percent of fermented flour coming from the levain, typical example would be 15% fermented flour for the VT Sourdough). Then, enter the amounts of storage starter you want to use. I provided both a firm starter and a 90% hydration starter, but you can change the hydrations of either starter to match the starter you are using. The amounts of storage starter are specified in grams. You also specify the hydration desired for the levain, and specify the percentages of any additional levain flours as a percentage of the total flour in the levain. After that, you specify the additional ingredients and flours in the dough as percentages of the total flour in the recipe.

Just a side note, I do the bakers' percentages based on total flour weight, since that is the best way to scale the entire recipe and understand the overall important percentages like hydration and salt, I believe. Often, in recipe books they don't include the flour coming from the preferments in the total flour used as 100% for the bakers' percentages. So, yes, you do have to play a little with the percentages to get them to match up with a recipe in a book that may not use the same system as I'm using there. However, you can still put almost any hearth bread recipe into the format in the spreadsheet. I've done this same spreadsheet for quite a few different breads, including the Thom Leonard and the Essential's Columbia, as well as various miches, ciabattas, focaccias, and so on.

Finally, you specify your "additional flours" as percentages of total flour weight. The labels on the left for the "ingredients 1-4" and for the "flours 1-5" can be changed to note the flours and ingredients you are using for the recipe. You can see I did that for the miche recipe.

Once you've entered all the items in blue to suit the recipe you want, it will tell you the amounts in each case that you need. If you change one of the inputs, the various amounts will be recalculated. For example, if you change the percentage of one of the "flours 1-5", then that flour's weights will change, and also the "main flour" will be adjusted so that the total flour is still as specified.

The other page of interest is the "summary page", which has the rise time calculations on it. Once again, the numbers that you change are highlighted in blue.

There are three sections to the "summary page". The top is for the levain rise time calculations. The middle is for the dough rise time calculations. The bottom has a "stage calculator" that will allow you to enter the fermentation of the dough in a series of steps, and it will tell you how far the fermentation has progressed in total. You will see an "average factor" that tells starts very small and grows to about 1.0 when the dough should be doubled, and grows to about 2.3 when the final proof is finished. The stage calculator is very useful once you figure it out, but you don't need it at first.

The first number you need to think about is the number labeled "starter speed factor", which sets the overall speed of your starter. Once you know how fast your starter rises by double when fed with a particular flour type or blend, you can set "starter speed factor" to match your starter's rise time. Then, you can calculate other rise times with this summary page. That number can be set in the levain section and in the dough section, since the levain and the dough may have different flours. So, you need to run a test dough or two with typical flours and note the time for them to double, preferably measuring the volume fairly carefully. I would suggest doing a hydration of about 80%, so you don't get too much of a "crown" to confuse matters. It makes sense to do one that is large enough that you aren't getting too much "small dough" effect in the rise time.

For example, you might build a test dough with about 200g of flour. You could make a test dough with 32g of firm starter, 180g of flour and 148g of water. It will be fairly wet, but if you put it in a good rising container that has vertical sides, you can measure the time it takes to rise by double the volume. You note that time, and then set "starter speed factor" on that summary page in the levain section so that a levain with an inoculation of 10% (20g flour in firm starter divided by 200g total flour in the test dough), a salt of 0% (no salt), and a hydration of 80% has a doubling time of what you observed for the test dough. Of course, set the temperature to match what the temperature was for the rise of the test dough. Once you know the "starter speed factor" setting for your test dough, it should be a good number to use elsewhere in the calculations, including in the dough section. However, I've noticed that my doughs rise faster than my white flour levains because the flour blend in the dough is just faster rising. So, you will probably find that the test dough rises a little more slowly than your typical bread does, so you can use a little bit higher "starter speed factor" for the dough, which you will begin to figure out. For me, the "starter speed factor" number for my doughs is about 15% higher than my "starter speed factor" setting for a bread flour levain.

Once you have "starter speed factor" figured out, then the rest of the numbers are just the characteristics of your dough and levain. The inoculation percentages are listed for the recipe that you did in the "bread calcs", so you can just use those inoculation settings most of the time. The other numbers are overall hydration, overall salt, also same numbers as in the spreadsheet for the bread calcs. The temperatures are for the bulk fermentation and the final proof.

The stage calculator just lets you enter times and temperatures in a series of steps. You can see how far your dough progresses in fermenting that way. If you set "starter speed factor" so that the doubling time is right, then the average factor will be about 1.0 at the point the dough has doubled, and it will be about 2.3 when the final proof is complete.

Notice that if you put your mouse over the text boxes with red triangles in them, you will see comments I have made trying to describe the uses of the various fields.

Comments

dolfs's picture
dolfs

Being an engineer by trade, I like your approach. While I can certainly make bread without it, this is something I had been thinking about. I had already developed my own spreadsheet for formulas and scaling. It also computes final dough hydration (including for ingredient such as eggs that contain substantial water), total cost based on ingredient cost etc. There are also tools on it to take published recipes and reverse them into percentage based formulas, and to compute water temperature from desired dough temperature, room temperature, preferment temperature, and mixer friction.

This spreadsheet I use all the time. I keep the formulas for the breads I make on additional tabs and when I want to make one, I copy the ingredient and percentage list to the main page, enter how much dough I want (depending on number of loaves, using bannetons of particular sizes etc), and it produces all measurements I need. 


--dolf

bwraith's picture
bwraith

Dolf,

Yes, I expected to hear that many TFL people have gone way down the road with spreadsheets. Mine is fairly simple and focused on hearth breads. I didn't worry too much about dough temperature, but I handle that somewhat by having a "stage calculator" that allows me to measure the temperature and approximate the progress of the fermentation, given the actual temperatures prevailing during the fermentation. So, if the temperatures aren't quite what I had planned during the planning stage, or if I have some varying temperatures I plan to work with by using a proofing box or some other method, I can calculate when to shape and when to bake.

You may find the rise time calculation part useful, even if just to trigger ideas. I find it is extremely helpful with sourdough recipes to understand the rise times and proofing times. First of all, starters do vary somewhat in how fast they grow or ferment, so it really helps to know how the recipe will work with your own starter. Also, I find many problems with recipes, as you encountered in one of the Leader recipes, and I always deconstruct recipes into my format and check them carefully when I am planning to do a new one. Also, you can get a feel for what the author of a recipe intended in terms of timing of the bulk fermentation and proof. Some are letting the bulk fermentation go much longer than others. Usually, the mix to bake time is sensible, and so you know they want you to shape earlier or later, is all. Other times, you can see that some error was made, or at least the author was working with a very different starter, because the overall fermentation time from mix to bake is just way too short or way too long to work with your own starter.

My education and much of my career was as an engineer, although some of it was spent in the financial business. Even when I was in the financial business, much of what I did involved mathematics and computers. 

Bill

slidething's picture
slidething

 Dolf or bwraith -

 I don't have Excel -don't really need it for the type of work I do - but very interested in your spreadsheets - Is there another way to get your spreadsheets - I have  Windows XPHome on the House "puter and Vista basic on my laptop I use at work.

 Thanks Guys ~

 Slidething

dolfs's picture
dolfs

Both our spreadsheets not only use basic spreadsheet features, but incorporate formulas in what's called Visual Basic for Applications. That last part makes it impossible to transfer to other spreadsheet programs, some of which will import Excel sheets.

I suppose mine could be adapted somewhat so the OpenOffice's spreadsheet (free) can handle it, but it would have to loose a lot of features, such as the ingredient database and the conversion to weights with fractions (3 1/4 oz) etc. 

I've been thinking of turning my work into a Java based program with a GUI so that Macintosh and Windows users alike could use it. It would incorporate the USDA nutrition database, with added costs information for accurate calculations/conversions from weight to volume, computing hydration, and producing a nutritional content "label" for your breads. It would also have a database to store your recipes. It is a lot more work than putting together a spreadsheet, however, and for now the need to bake and this thing called "work" has kept me from it. Who knows. 


--dolf

My Bread Aventures 

mac9000's picture
mac9000

"I notice that I can use the spreadsheet on a Macbook with Microsoft Office 2004 for Mac installed on it."

 

It can also be used on a PPC Mac mini running Office v.X for Mac.


~J

dolfs's picture
dolfs

I am a Macintosh user myself (since 1984), and I actually developed my spreadsheet on the Mac, using Office 2004. I did find though that, when using VBA macros, Excel for the Macintosh becomes unstable. I've had it crash many times. Once the document was apparently corrupted, I could only resurrect it by opening it on the PC (Parallels is wonderful), editting it, resaving, and then back to the Macintosh.

So it is possible that some of you may encounter this crashing behavior at times when using the Macintosh. 


--dolf


See my My Bread Adventures in pictures

bwraith's picture
bwraith

Hi Dolf, Mac9000,

Thanks for the advice on using the VB macros on a Mac. I wrote the spreadsheet on a regular PC w/WinXP, so no testing has been done on Macs, other than just noting it came up on my Mac using Excel 2004.

Thanks, Bill

dimitrisbizakis's picture
dimitrisbizakis

Hi Bill, realy intresting calc and seems to be right on the spot!
How can i change the temps to inputing just C without messing the whole sheet up?

bwraith's picture
bwraith

I don't know if you were looking at the more recently posted spreadsheet or the older excel spreadsheet. I believe in all cases, without carefully examining it, that the inputs only are in Fahrenheit. I believe in most every case where there is an input in Fahrenheit (unless I blew it and used a reference to the Fahrenheit input directly in another calculation) there is a cell next to it that converts to Celsius. Yes, you could use the cell next to it as an input in Celsius. However, I would suggest creating an input called "Temperature Units" which can be set to "C" or "F". Then, change all the cell formulas that convert the Fahrenheit input to Celsius to have logic (this is not a formula, just the logic of it) something like: (If Cell("Temperature Units") equals ("F") then "This cell" is set to ConversionFtoC("Input Cell") else If Cell("Temperature Units") equals ("C") then "This Cell" is set to "Input Cell").

This way you can switch the units and still use the blue input cells as inputs in the normal way. Otherwise, if you want to input directly to the Celsius cells, you will overwrite the conversion from F to C. If so, then you might want to remove those input cells and move the Celsius cells in their place (keeping the references to the Celsius cells intact) and make them blue, so it is clear those are now the input cells.

dimitrisbizakis's picture
dimitrisbizakis

Ignore the upped comment...the answer was so obvious...u just type the Celsius cel...

Another question...

The temp that needed in summary page is the temp's of the Dough or the room-proofer temps?

bwraith's picture
bwraith

So, the temps in the spreadsheet are generally always referring to a constant temperature in the dough itself. Of course, arranging the temperature to be constant in the dough itself is a big problem. Also, I frequently engage in strategies to cool the dough in a refrigerator or incubator, as I prefer the flavor in my breads from cooler, longer fermentations around 60F. So, in the newer Google Spreadsheet, I have included a section down at the bottom of the Summary sheet that attempts to predict the internal temperature of the dough as a function of the ambient temperature. It uses a schedule of ambient temperatures and a heat transfer coefficient for each of several stages. Of course the heat transfer rate is a function of the container material and shape, and also the size of the dough. So, you have to discover the transfer rates through experimentation. If the dough is very small the rate will be very fast, so maybe the spreadsheet isn't that useful for that. However, if you have a large dough in a plastic container, the temperature may fall from 75F down to 40F in a refrigerator over many hours and the predictions in that lower section using the temperature stages is far more accurate in that case, once you discover the right heat transfer rates. Once you have the correct heat transfer rates, you can vary the schedule or ambient temperatures to discover how this may affect the rise times. It is better to create a schedule with shorter times at the beginning and longer times at the end, since the temperature will change quickly at first and then slowly settle in to the final temperature. I have that codified in my inputs in the recently posted spreadsheet as you can see in the formulas. However, any schedule can be input by hand. I use the formulas on the inputs to make it easier to create the schedule and change it more quickly. You can compare the final temps at the far right to the actual measured temperatures in the dough as it falls or rises in temperature and adjust the heat transfer accordingly. I have found that the dough is always a degree or two warmer than the predictions, which you will see as an offset in my temperature formulas in the stages. I'm not sure why that is, but maybe it is that the fermentation activity warms the dough. However, I don't know if there is enough heat generated by the fermentation to cause that effect. 

bwraith's picture
bwraith

Here is a Google Spreadsheet version of the Sourdough Rise Time Spreadsheet that I have ported and modified and added to in small ways. Much of it is exactly the same, but it is much easier to share across platforms and access anyplace you have internet and a browser as a Google Spreadsheet. If it is useful to some of you, great. It is full of all kinds of doubtful modelling ideas, but I have found it helpful over the years when making up recipes or to modify rise times based on different temperatures.

bwraith's picture
bwraith

There was a question about using the spreadsheet in Celsius. I added what I think makes sense to allow switching the units used for temperature input and posted another version. I have not tested it, however. At this point, I'm not even sure if I've shared the folder here in such a way that the spreadsheets can be copied and used by someone else. In order to get an editable copy of this, I believe you can log in to Google (an account is free if you don't have one), go and visit the link above, select the spreadsheet you want (second one is the new version labeled v0.1), click to "open" the file. At this point you have a read-only version opened. However, you should then be able to go to the  "File" link and click to make a copy of the file. The new copied file should then be your own copy within Google Docs, and you should have complete control of it, including making changes to it.

dimitrisbizakis's picture
dimitrisbizakis

Wow...very nice, you are sure a lot helpful my friend!