Lately, I’ve seen people saying things like “a 4-week-old sourdough starter is too young” to justify someone’s problems with their bread or starters. This statement is just wrong and very discouraging for new bakers, or people on a budget who can’t just throw flour every day for feedings.


Two weeks (as a rule of thumb) should suffice to have an active and powerful starter. Let alone 4 weeks!. In fact, depending on the method you used to create your starter, you might be able to make bread in just a week!

Chances are that the age of your sourdough starter has nothing to do with the problems you might be having. In this series of posts I’m going to delve into the science of your starter so you can troubleshoot whenever you need. Although, I hope you only need to troubleshoot it once!

WHAT DEFINES THE STRENGTH OF YOUR SOURDOUGH STARTER?

It’s not time, it’s THE NUMBER OF ACTIVE BACTERIA present in your starter. If your sourdough starter is not ready after 2 weeks (and depending on the method, maybe just a week), your feeding schedule probably needs adjustment. Either you’re following a fixed schedule instead of refreshing the starter when is ready, or you’re using the wrong ratio and not introducing enough nourishment for all the microorganisms to reproduce. Let’s dive into it:

BASICS OF SOURDOUGH BACTERIA

Bacteria in sourdough follow a 4-phase growth curve: Lag phase, exponential phase, stationary phase, and death phase, (For more of this go check this post where I tell you all about it). During the lag phase, they’re not multiplying yet; they’re just checking the environment and synthesizing the proteins and products they need to start multiplying (growing). At this stage, whichever ratio you used to feed your sourdough starter introduced some nutrients for the bacteria.

The second phase involves the exponential growth we’re all familiar with; the duration of the second phase(how much the starter is going to grow) purely depends on how much food there is available for the bacteria. Or better said, how many grams of food per bacteria were introduced. Let me explain:

Imagine a family of 4 people that has 4 cupcakes; they get one cupcake per person, they will run out of cupcakes fast, and they are not going to get a lot of weight because they only ate one cupcake each. Now let’s say we have the same family, and instead of 4, we have 12 cupcakes; then they get 3 cupcakes per person, it’s going to take longer to finish them all, and they will gain more weight because there was more food, right?

Same with your sourdough starter! Smaller ratios mean that the food is going to run out faster, and the growth (bacteria multiplying) is going to take place for a shorter period of time. Now let’s say you used a 1:3:3 ratio (like the family), the bacteria have a lot more food, so they’ll be eating for longer; therefore, it’ll take a longer time to finish all food.

What happens after the bacteria eats all the food? Bacteria multiply as long as they have food (energy), once all the food is depleted, they can stay active for a while, this is what we call the “peak” (the stationary phase), and the reason we say this is the best moment to use your sourdough starter is that it’s when there’s the largest number ALIVE AND ACTIVE bacteria.

After the peak, bacteria start going dormant; some die too (death phase). When using a 100% hydration starter (Keep in mind that gluten-free flours behave a bit differently because of the lack of gluten), this moment usually occurs at the same time the gluten network starts breaking down. That’s when we see the starter collapsing (there are more variables involved in this, but for now, let’s imagine the kitchen is at around 20C, not too cold, not too warm, so neither the bacteria growth nor the gluten in the starter is compromised because of the temperature).

WHY IS MY SOURDOUGH STARTER NOT DOUBLING?

One of the main problems I see is that people refresh their sourdough starters based on time (fixed schedule) and not when it’s ready. So when you take part of your starter out too early and introduce new flour and water, what you’re really doing is reducing the number of active bacteria before they have a chance to multiply. What you’re doing is bringing more cupcakes to the family but taking away a few members, so yes, there are lots of cupcakes, but not enough people to eat them in a reasonable time. And the more you do this, the more you feed your starter too early, the more bacteria you’re taking away, and the more you’re reducing the fermentative power of your starter by introducing unfermented flour. It might get to a point where the number of bacteria is so low that you might not see any growth in maybe 12 hours! (Even though they’re still working hard multiplying!)

Basically, you are keeping your sourdough starter in a continuous lag phase or a very early exponential phase.

HOW CAN I FIX MY SOURDOUGH STARTER?

Easy, just WAIT!, leave the starter at room temperature for a whole day; it’s not going to grow mold, and it’s not going to go bad (if it does, then your starter was already contaminated with other microorganisms). If the problem is a very low number of bacteria, they need time to get out of the lag phase and get well into the exponential phase. Wait, and most likely, you’ll see some growth, maybe in the form of small bubbles, maybe you can smell it, or maybe you can even see the dough growing a tiny bit.

If you don’t keep a large amount of starter (less than 40 g total), you can add more flour and water without discarding anything and wait for it to grow again; then you can start with regular feedings. If you keep a larger amount, you can discard some and refresh it. At this stage, since the problem was (most likely) the low number of bacteria, you don’t want to give it too much food all at once because that might take too long to ferment, and you’re going to get frustrated. I would aim for a 1:1:1 ratio for a couple of feeds until you see obvious signs of activity and the starter growing. Then wait for it to peak, and decide which ratio works better for your situation.

Wrapping up

Feeding ratios are another big thing when it comes to sourdough starters, in part II I’ll tackle feeding ratios and some outrageous advice I’ve seen people tell newbies. Things like “if your starter doesn’t double in 4 hours then it’s not powerful enough”. If you’ve heard that before, stay tuned! And if you have questions write them in the comments so I can try to respond as best as I can.

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Happy baking!

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