Lactic Acid and Yeast Fermentation Predictive Model: A Tutorial

Fermentation is a complex system. In baking, it involves a couple of variables that are chemically and biologically dependent on one another to produce successfully leavened dough. As we know, fermentation can undergo via spontaneous process or induced fermentation. The difference between the 2 is the use of fermentative agent wherein the former uses microbial agents naturally thriving on the raw materials themselves while the latter depends on cultured microorganisms. Sourdough in baking is an example of a spontaneous or natural fermentation while use of dried baker’s yeast is, obviously, under induced fermentation.

 

Baking pizza crust (or plain bread) can be really intimidating since fermentation temperature and time can be really confusing. Some recipes would recommend you to use short fermentation time and warm environment while some would opt to go for longer fermentation time at cooler temperature depending on their convenience. In addition to the complexity, fermentation time is greatly affected by the amount (in terms of baker’s percent) of sourdough starter (in sourdough baking) or baker’s yeast; more fermentative culture would equate to faster fermentation. Although some recipes would give you an eyeball on the time length for the yeast and lactic acid bacteria to produce their desired carbon dioxide, alcohol, and lactic acid by-products, some are more based on experience than science. In addition, it would also be nice to create your own recipe and fermentation setup without risking its efficiency.

 

I have stumbled upon a post by a fellow pizza-enthusiast in pizza making forum. TXCraig1 posted a table where you can predict the time needed for a sourdough to be fermented given a starter amount and fermentation temperature. Here, dough is deemed to be ‘fermented’ when it achieves a point where it is ready for baking or visually have risen enough. With this tool, no more guess work is needed when preparing sourdough bread or pizza crust – it is already laid out in the tool ready to be used. It provides a beginner baker the confidence to pursue sourdough bread baking. Moreover, sourdough preparation can be planned ahead through this without hesitating if the dough will rise enough before it needs to be served.

 

sourdough model

source: http://www.pizzamaking.com/forum/index.php?topic=22649.0

 

The above chart depicts the relationship between %sourdough starter, fermentation time, and fermentation temperature. Although the computation applied to devise the tool is awfully complicated, the chart is extremely easy to use. First row corresponds to the amount of starter used in the dough in relation to flour (baker’s % starter), while first column is the fermentation temperature in Fahrenheit. The data that intersects the first row and column is the total fermentation time in hours needed for a dough with a specific % starter and fermentation temperature to be ready for baking. For example, a sourdough with 4% starter needs to be fermented at 70oF for 23 hours (1). Consequently, a dough prepared with 2% starter needs to be stored at 55oF for 104 hours (2). See the chart below.

 

1

Easy, right? Simply mix and match fermentation temperature with %starter and you would be able to determine the time needed for your dough to be ready. The chart can also be used to determine the %starter you have to prepare if your schedule allows you to only ferment your dough for a specific time. First, determine the temperature your dough can be stored. Find this temperature in the chart and slide horizontally until you reach your preferred preparation time. Project your line upward to determine the required %starter. For example, you need to showcase your sourdough after about 10 hours. You also learned that the temperature in your kitchen is slightly cool (64oF). The chart clearly tells you to use a 40% starter. Any lower than 40% would require more time for fermentation. See chart below.

 

2

 

For some expert bakers, they prefer to perform multi-stage fermentation or setups that have 2 or more fermentation steps. For example, a baker wants to store a dough in a chilled temperature for a specific time and transfer it to another temperature with different condition. The chart can be used to determine the remaining fermentation time needed for a dough be baking-ready. If a baker decided to bulk ferment a 1% dough at 70oF for 10 hours then ball and store it at 74oF, how long does it need to be fermented at 74oF for it be ready for baking? Start at the intersection of 1%starter and 70oF in the chart (step 1). The chart will tell you that it needs 33 hours for the dough to be ready. However, the dough stayed for only 10 hours at 10oF. Do a simple subtraction: 33hours – 10hours = 23 hours remaining for the dough to be ready (step 2). Looking at the chart, we could see that every data up and down the remaining time column is a time and temperature combination to finish the fermentation. Since we want to know the last step fermentation time at 74oF, we go down the column and pick the corresponding time which is 18 hours. See chart below. You can also apply the same method for setups that require several fermentation stages.

 

3

 

Txcraig1 also devised a programmed datasheet to determine the optimum %starter you need to use if you plan to stage a multi-step fermentation. https://docs.google.com/spreadsheet/ccc?key=0AuvMQbzk5INUdGZScWx6U2lYSEtZVkJuVGJiR19NaXc#gid=0

Here, you simply input the fermentation time-temperature combination and the datasheet would show the % starter you need for your recipe. As a bonus, it also shows you an example sourdough recipe with ingredients broken down depending on your preferred dough hydration and pizza yield. Just make sure to enter data only on the topmost yellow cells.

The tools made by TXCraig1 was highly regarded by the forum community. It actually made TXCraig1 produce another tool specifically made for induced fermentation. Below is the baker’s yeast predictive model.

 

bakers yeast model

Source: http://www.pizzamaking.com/forum/index.php?topic=26831.msg285982#msg285982

 

Similar with the sourdough predictive chart, this model determines the fermentation time needed for a dough to be ‘ready for baking’ for a specific fermentation temperature and amount of baker’s yeast. The first 3 rows corresponds to the % baker’s yeast used in a recipe. Since baker’s yeast comes in many forms (active dry yeast, instant dry yeast, and compressed yeast), the equivalent for each is written for the 1st 3 rows. The first 2 columns are the values for fermentation temperature in celcius and fahrenheit unit. The intersection between fermentation temperature and %baker’s yeast would be the estimated time when the dough is deemed ready for baking. For example, a dough prepared with 0.1% instant dry yeast and stored at 68oF is expected to raise enough for baking after 7 hours. It can also be seen from the chart, greater amount of fermentative culture would need less fermentation time while colder fermentation temperature would require longer fermentation time and vice versa. Similar to sourdough predictive model, you can also use this tool to determine one of the values (fermentation time, fermentation temperature, and baker’s yeast amount) if the other 2 is given.

 

4

 

Although these tools are extremely helpful, it must be used with caution. Every parameters must be considered. Txcraig1 even rationaled that at extreme temperature range, the tool may deviate from being accurate. Almost all of the readers from the pizza making forum community who stumbled upon this chart tried to apply this on their sourdough making. For most of them, the chart was extremely reliable and produced results that are same with what the tool has predicted. Some did not get great results basically because they did not understand how to use the chart properly. I suggest that when using this tool, you take note of all the variables you used in your experimental baking if it doesn’t follow your setup somehow. In doing so, you can tweak the tool and add tolerance to each values.

 

In conclusion, I recommend that you bookmark or save these tools. They are extremely helpful not just for expert bakers but for beginners as well. These tools have worked for me in crafting the tastiest pizza crust (with the help of my Mighty Pizza Oven of course!). Let me know if they did to you too.

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