>>> 1/3/13 NOTE: The chart below has been revised to include the effects of the Lactic Acid Bacteria in the SD culture <<<
I have also slightly adjusted the color zones. The changes to the data in the original green zone were negligable. I will post a recap of the changes down the thread.
>>> 1/6/13 I added a section here: http://www.pizzamaking.com/forum/index.php/topic,22649.msg230690.html#msg230690 that shows you how to use the tables to calculate the starter quantities and fermentation times with multiple fermentation temperatures.>>> 1/6/13 Here is a link to a spreadsheet that automates the calculation of starter% given multiple fermentation stages: https://docs.google.com/spreadsheet/ccc?key=0AuvMQbzk5INUdGZScWx6U2lYSEtZVkJuVGJiR19NaXc#gid=0 more details here: http://www.pizzamaking.com/forum/index.php/topic,22649.msg230734.html#msg230734
This model should help identify a starting point for starter quantity and/or fermentation time in a new sourdough-leavened dough. It’s a generalized model, so as you would expect, changes in culture, hydration, salinity, dough mass, etc. will likely affect the fermentation time; therefore experimentation will be necessary to fine tune a specific dough formula. Notwithstanding, the model shows good predictive ability with typical doughs.
The model was built around real-world 75F data. This is a typical temperature coming out of the mixer, and I had a wide range of data at this point. I then used the temperature vs. growth model for C. milleri
(a typical yeast found in sourdough cultures) from Gänzle et al. (1998) http://aem.asm.org/content/64/7/2616.full.pdf
to expand my model across the viable temperature spectrum.
The chart below predicts total fermentation time in hours at specific starter quantity and temperature combinations. I included all the predicted data because I thought it was interesting. I don’t however believe it is all equally reliable. For example, the model assumes 100% of the fermentation takes place at the specified temperature, and the farther away from 75F you get, the longer it takes the dough to get to that temperature thus skewing the results (not to mention the farther the model must extrapolate from the original regression). Also, as fermentation times become very extended and once you go much past 40% starter, I think there is significant risk of the proteolytic enzymes catastrophically denaturing the gluten matrix in the dough. I color-coded the chart to indicate what I believe to be the relative reliability of the predictions. The color codes are just my gut feel – your results may vary.
The graph following the prediction chart shows how the model compares to real-world data at 65F, 70F, and 75F. Only the 75F data (round black markers) was used to build the model. The black diamond and triangle markers (real-world 70F and 65F data respectively) were overlaid after the model was built as a predictive test.
I’m curious to hear how the model output compares to other people’s experiences.