Understanding Sourdough Part 2

In the last issue (see Bakers Journal, January/February 2017) I shared the results of a personal experiment I conducted with a sourdough starter (or levain) to determine just how resilient an established starter can be. Leaving two levains in my refrigerator, one for seven months, one for three months, I revived them with no problem over the course of four days.

To help me understand why this works, I had a discussion with Dr. Michael Gaenzle, one of a handful of individuals in the world who has a PhD in the microbiology of sourdough. Gaenzle explains that in a single gram of levain there are one billion organisms, and as long as you have one living organism remaining, the culture can be revitalized.

Now that I have determined that a levain is very robust and can be abused and returned to its full leavening power within a few days, I will now take you through the process of starting a sourdough culture.

As pointed out by Raymond Calvel in his book The Taste of Bread, many people try to make a sourdough culture with a variety of initial ingredients – such as yogurt, sauerkraut, or grapes – to kick-start the process. But by the time you have arrived at the point where you can ferment bread, there is no trace of that starter ingredient. A few classes can be found where a whole host of fruits are fermented to be used in a sourdough, but professor Calvel notes that it is really best to not use any other ingredient other than flour and water to make your culture.

As the pH of the dough slowly lowers, the level of acidity increases. A natural selection of bacteria and yeast occurs. The pH needs to drop below six for the lactobacillus sanfranciscensis to begin its lifecycle. Other bacteria, which require a stable pH environment, are taken over by the lactobacillus sanfranciscensis. The L.S. grows at a faster rate than other bacteria.

You can start a successful sourdough culture with a wide variety of flours, or a variety of flour blends. From my experience, flours with many additives seem to lag in development time. Because of this I prefer to use an untreated whole-grain flour. The wild yeast and bacteria that are present in the flour and in the environment (known as microflora) lead to the fermentation, and this is achieved through enzymatic activity—the breakdown of the starch to a simple sugar from the amylase.

Organic whole-grain flours work very well – especially organic whole grain rye flour, as rye flour has a higher diastatic level, which means the availability of additional sugars in the rye kernel are made available for fermentation; thus, the sourdough seems to be more active earlier.

The process for making a liquid levain:

Mix 100g flour with 100g water at 21 C and leave undisturbed and covered in a container for 24 hours. You will see little to no activity. Discard 160g, keeping 40g of the mixture, and then add 100g flour and 100g water at 21 C and again leave undisturbed for 24 hours.

You will now see some fermentation.

On the third day you continue with the same feeding schedule but will now move to twice-a-day feeding. Always keeping 40g of culture, discarding the rest, and adding 100g flour and 100g water with every feeding.

People often state that they don’t like discarding unneeded starter, but until you are on about day 10 the aroma and flavour are undesirable and need to be discarded. Beyond day 10 you can start to add the 200g of discarded culture to start forming your bread dough.

As the culture goes through the natural selection of bacteria, through days three to seven, the culture will have a very unpleasant aroma. But as the level of activity increases and the culture is on its intended journey to become a levain, the aroma will begin to improve, the level of activity increases and the aroma will start to be more desirable.

There are variables and obstacles to be aware of when making a culture. The ambient room temperature, the falling number of the flour (how enzyme active the flour is, as tested by the miller), missing a feeding, etc. For making a levain, understanding water temperature and your environment is key to your success. In the end, the levain likes consistency. So the more consistent you can be, the better.

But what happens when you get busy and miss a couple of feedings or just a single feeding? The protease enzymes diligently continue to break down the protein. If you miss a feeding, you will see the consistency of the culture get thinner. This is when on your next feeding you hold back 5-10g of water and add a dash of salt. The water will help to bring the culture to its correct consistency and the salt strengthens the protein, which also assists in bringing the culture to the correct consistency.

As the culture becomes more and more active, water temperature plays a significant role in maintaining the culture’s health. One of the most important concepts is that sourdough culture requires feeding when it has reached its highest point and prior to it starting to break down and collapse. You will see a fissure across the top of the sourdough, signifying that it has reached its maximum height and it is ready to be used to ferment bread.

For example, my sourdough at home requires 8 C water for a 12-hour feeding cycle as my home is usually around 21 C. The sourdough is very active. If I were to use water at 21 C the culture would ripen in well under 12 hours and already be collapsing or collapsed. In our bakery the temperature is usually between 19 C and 20 C overnight as there are no ovens running, and as a result we use 10 C water in the bakery. If your bakery is warmer or cooler you need to determine, through trial and error, the ideal water temperature you require in your environment with the particular flour that you are using.

How do you know when your culture becomes a levain and is ready to use in a dough? If you are using a twice-a-day feeding schedule, the sourdough will be at its high-water line in 10 to 12 hours and will have risen approximately three times its original height.

You can use a once-a-day feeding schedule, but you have to reduce the portion of levain you are keeping; instead of 40g, you only keep 20 to 25g, depending upon your room temperature. You also have to lower your water temperature to ensure that at the 24-hour mark your culture is still at the high water line. I find that a 24-hour feeding cycle results in a levain with slightly lessened leavening power.

You can also maintain a three-times-a-day feeding schedule wherein you would increase the portion you keep; instead of 40g, you would keep 55 to 60g, and depending on your environment you would increase your water temperature with a goal of having the culture be at its high-water line in six to eight hours.

Seasonally you will come across temperature fluctuations in your bakery, so you have three main variables to adjust: increase or decrease your water temperature; increase or decrease the portion of levain you hold back to feed the next batch; or, in hotter conditions you can add 0.1 per cent salt at a starting point to also slowdown the culture. Remember to decrease the weight in salt that you add to the feeding from the final dough formula.

Embrace and enjoy your sourdough experience.

Alan Dumonceaux is chair of the baking program at NAIT School of Hospitality and Culinary Arts in Edmonton. He can be reached by email at adumonce@nait.ca.