Part II — How to Make Sourdough More (or Less) Sour (2024)

If there is too little acid in the ongoing culture, undesirable microbes (such as leuconostoc or mold) can multiply and infect the culture. If there is too much acidand an overripe culture, yeast populations are compromised and enzyme activity may get out of hand. To avoid this in our “more sour” loaf, we limited the proportion of whole rye flour to 20% and were careful not to go too far when allowing the culture to mature to a more ripe state.

We made significant changes to the levain percentage for these breads. Our standard County Sourdough recipe has 16.6% of the total flour pre-fermented in the levain, our less sour version has a much smaller levain, containing only 10.5% of the total flour, while our more sour bread has a large levain containing 35% of the total flour. The reason for the difference is the presence of salt in the main dough. Salt inhibits the acid producers more than the yeast, which means that once the levain is mixed into the main dough, the ability to produce acid is somewhat diminished. To achieve a “more sour” bread, it’s important to add a larger quantity of acid and acid producers to the main dough.

For the “less sour” loaf, using a small percentage of levain not only limits the amount of acid in the loaf but also slows down fermentation. Slower fermentation allows enzymes in the flour to break down starch into sugar, further limiting the perception of a sour taste.

In addition to getting ready for the addition of salt, we have also incorporated similar maturity, temperature and flour choices as in the mother culture. For the less sour version, we use the levain a little earlier in its cycle than we could for the mother culture — when it is well-risen but has not yet reached its peak. This type of small, less ripe levain has been popularized by Chad Robertson and Ken Forkish in their bread books.

Many bakers’ normal practice is to take part of the levain and use that to perpetuate the ongoing culture. The best way to do that with a small, young levain is to take the portion needed to mix the main dough, then leave the remainder to continue to ripen to full maturity before using it to perpetuate the culture.

Main Dough — Maturity is Key to Controlling Flavor

In considering how much whole grain to put in the overall formula for these breads, we increased the whole grain in the “more sour” loaf from 15% of the total flour up to 20%. For the less sour version, we not only reduced the proportion of non-white flour to 10%, but also switched from whole grain to high-extraction flour and omitted the acid-friendly rye altogether. High-extraction flour can be made easily at home by passing whole wheat flour through a fine strainer to remove the larger bran flakes. As Debra Wink points out, the bran in whole grains buffers acidity and allows the acid producers (LAB) to produce more acid in a more ripe culture. And rye flour produces sugars in the dough that feed the LAB that produce acetic acid, which is more flavorful and noticeable than the other main sourdough acid, lactic acid.

Since the larger levain of the “more sour” loaf carries more enzymes (that degrade protein) into the main dough, we used higher-protein bread flour (instead of AP) for the white flour portion of the loaf and added one extra fold to the bulk fermentation to help ensure good structure.