Frequently Asked Questions
It is incredibly difficult (and nearly impossible) to kill a sourdough starter.
Check out this video below, “50 Ways to Kill Your Starter,” where I try to kill a starter using all of the most common mishaps. It is nearly impossible.
The video is set up with chapter breaks for the most common mishaps. Scroll through the chapters using the slider at the bottom of the video.
Most likely not. Scrape out any small amount of soft or liquid starter remaining and add it to a clean vessel with 30g flour and 30g water. Do not discard or refeed. It will likely reactivate in a day or two.
Check out this video clip:
No. I’ve done experiments where I mixed a 5% bleach solution and added it to my starter and I could not kill it.
Check out this video clip:
No. Resume your normal feeding process the next day. After five days of 1:1:1 feeding and discarding, 99%+ of the “wrong” flour will be gone from your starter.
Check out this video:
The most obvious answer is to keep a dehydrated backup of your starter, but if you had done that, you would not have clicked on this question!
If you do not have a backup, look around your kitchen for a tool that might still have some of your old, dried starter on it – a towel, a spoon, the tip of your thermometer, a bowl, a banneton, a banneton liner, your countertop, your cabinet handles.
You only need a very, very small (dried or wet) amount of your prior starter to revive it. Add whatever you can find to 30g of warm filtered water and let it sit for a day or two, then add 30g of flour and see if it reactivates in a day or two. You may be surprised.
If you have recently baked a loaf of bread, some people claim (I have not tested it) that you can recover a starter from a piece of baked bread. I am skeptical of this method. All of the yeast cells were likely killed in the oven once the temperature reached 130F/54C. Although it is unlikely you could recover a starter from a baked loaf, you may still wish to give it a try. You need a very small number of live yeast cells to reactivate a starter.
To try this method, put a piece of bread into a jar with filtered water and let it rest for a few days. Watch for any bubble activity. When you see some bubble activity, mix 30g of that water with 30g of flour and wait for it to react and revive. If it does not reactivate in two days, then you are just creating a new starter, not resurrecting your old one.
No. Mold is dangerous and it has tendrils that penetrate deep below the surface. If your starter has mold on it, throw it away and restore a backup, or make a new one. (Note: Always keep a backup of your starter!)
A healthy starter should resist mold growth, even sitting uncovered on your countertop at room temperature. The starter culture develops a pH level (acidity level) that is hostile to mold and other common pathogens.
It is incredibly unlikely (probably impossible, but I am not a medical professional) for a human virus to propagate in a sourdough starter culture.
Be patient. Sourdough starters take some time to mature. If you are lucky, your starter may be strong enough to rise a loaf on Day 7. It is much more common for it to take 10-14 days. And some people say it takes 30 days for a starter to achieve full rising strength. Your starter will also continue to strengthen and mature over time. Some bakers say it take one full year for a starter to achieve full strength and flavor maturity.
Yes. The lactic acid bacteria in your starter creates acetic acid, which is essentially a type of vinegar. This odor is very common. Smell your starter routinely. If your starter becomes very acidic, it can lead to premature overproofing of your loaves. See additional FAQs here for how to de-acidify your starter.
Yes, this is a normal byproduct of the fermentation process. If your starter smells like acetone, it usually means that it has consumed all of the available food and it needs to be fed.
No! It is nearly impossible to kill your starter by refrigerating it. Inspect your starter. If it is not moldy, you can usually recover it. It may be covered with a dark gray liquid on top. This is very common. If you smell it, you will smell that it is alcohol, a common byproduct of the yeast when it has consumed all of the available food.
How to Recover a Neglected Starter:
If your starter is covered with a layer of gray liquid (a.k.a. “hooch”) pour off that liquid, then scrape off the gray layer on top. You will likely see a beautiful cream-colored layer of perfectly good starter below the gray layer. Scoop out 30g of that starter into a fresh, clean jar, add 30g of flour and 30g of water. Stir it up and keep it warm. Your starter will likely recover in a day or two. Do not discard and refeed until the starter is completely covered with bubbles on top. Discarding and feeding a weak starter before it has peaked only makes it weaker. Be patient.
Here is a video clip showing both methods of including and excluding hooch. Both worked, but by stirring in the hooch, that recovery took one day longer.
Spread your starter on a piece of parchment paper. You can cover it with a second piece of paper or leave it in the open air. Let it completely dry out. It may take two days or more.
Once your starter has completely dried, break it up into small bits and store it in an airtight container in your pantry. You can also freeze a dehydrated starter. A dehydrated starter will keep “forever.”
Recently, some 4,500-year-old dried starter was found in Egypt, and it was rehydrated and used for baking. See article below.
This video clip demonstrates how to dehydrate your starter:
Check out this handy guide “How to Rehydrate a Dried Sourdough Starter.”
No. Your starter can give off many different odors. Common smells include:
- Alcohol
- Nail polish remover (acetone)
- Vinegar
- Stinky cheese
- A locker room
These odors are the natural byproducts of the fermentation process. And you may smell different odors based on the type of flour you are using (e.g., I think rye flour smells like vomit), the temperature of your starter and your specific microbe population.
The only smell to be concerned about is if your starter smells like mold. Once your starter goes moldy it is unrecoverable, but this is very uncommon. A healthy starter will resist mold growth. Consult a second opinion before assuming your starter has gone moldy. It is an uncommon occurrence in a healthy starter.
Probably nothing. If your starter gets completely covered on top with bubbles but does not rise, it is healthy but may just be a wet mix. Try reducing the water in your next feeding and see if you have different results.
Also, the type of flour you are using can impede the rise of your starter. All-Purpose flour, for example, will not rise as robustly as a blend of bread flour and whole wheat flour. Different mixtures or types of flour will cause your starter to rise differently. I strongly recommend at least 50% whole wheat flour.If your starter is made with rye flour, it often will not rise as vigorously as others.
Lastly, your starter’s rising strength is highly dependent upon its temperature. A cold starter will rise very slowly. A warm starter will rise quickly, but it can also collapse quickly because the gluten content breaks down more quickly in warm temperatures.
If your starter reaches a temperature of 130F/54C, the yeast cells will die off. Note, the die-off occurs when the actual starter temperature reaches 130F/54C (not the ambient temperature). For example, if you are storing your starter in your oven with the light on and you accidentally turn on your oven to 500F/260C, the starter will not reach that temperature for some time.
If you think you killed your starter with heat, always use a probe thermometer to take the temperature in the center of the starter. If it is below 130F/54C it is still alive, even if it was exposed to a higher oven temperature for a short time. If your starter is somewhat liquified, it is usually a good sign that it is still alive and can be recovered.
No. The die-off temperature for your starter is 130F/54C. At 90F/32C, your starter will rise quickly, become more liquified quickly and will favor the acidity over the yeast. It is possible to keep a starter at this temperature, but during the warmest days of summer, I prefer to keep my starter in the refrigerator and take it out only when preparing to bake. If you keep your starter in the refrigerator, most sourdough bakers feed it once per week or two.
No. The clear liquid is either water separation (harmless) or “hooch” which is ethyl alcohol, a natural byproduct of yeast fermentation.
If your starter has not risen and fallen, it is water separation. If your starter has risen and fallen, it is hooch.
Many new sourdough bakers mistake water separation for hooch. It can only be hooch if the starter has risen and fallen.
Try feeding your starter a high feeding ratio (e.g., 1:5:5) and discard and refeed right after the starter rises and peaks. This is known as the “peak-to-peak” method.
See the video below, “Give Your Starter a Bath” – for an example of how to de-acidify your starter by giving it a water bath.
Also see the FAQ page: Starter Strengthening.
When you change the type of flour you are feeding your starter with, a few things can happen:
- Your starter sometimes needs time to adapt to new types of flour. Different flours contain different types of starches and enzymes. When you change your flour type, it may take a week or two for your starter to adapt to the new flour.
- Some flours are more or less absorbent of water. For example, when changing your starter from whole-wheat flour to all-purpose flour, the whole wheat is a “thirstier” flour. So, if you feed your starter all-purpose flour at the same feeding ratio as you were feeding the whole wheat, the starter be a very wet mix which may not rise.
All-purpose flour has less protein (i.e., gluten), than other flours and it does not absorb water as well. It is very common for an all-purpose starter to be flat and wet compared to other starters. It can be equally as strong but without showing a tall rise.
Learn to read the bubbles on the surface of the starter to gauge its strength and peak.
You can also try mixing a drier mix (30% less water) and an all-purpose starter may show its rise more clearly, but it is not required. A wet, flat starter can be very strong as long as it is vigorously bubbling within 4-6 hours after feed.
As an experiment, if your starter is very strong and rising quickly, give it a very wet feeding (for example, 1:1:2. The starter will not rise but will be very vigorously bubble rather than peaking in height. This starter has exactly the same strength but does not show the rise because it cannot lift the weight of the extra water you added.
I like to experiment with wetter and drier mixes from time to time when feeding my starter. This technique will help you learn your starter’s behaviors.
It means you are over-feeding your starter. You’re discarding and refeeding your starter before it peaks (which actually weakens it).
The first rule of starter feeding is: Never discard and refeed a starter until it peaks. Although your starter is “doubling” it is not “peaking” because it apparently has the potential to triple.
By feeding twice a day before it peaks, you are discarding “uneaten” flour and a diluted yeast population. When the starter peaks and begins to fall, that is when the yeast population is at its peak and the food source is being fully consumed. The best time to feed your starter is just past peak if you are trying to grow and optimize the yeast population. If you are simply trying to maintain your population, you can let it rise and fall before refeeding.
If you still want to feed twice a day, try reducing your feeding ratio to 1:1:1 and see if it peaks in 12 hours. Different feeding ratios should just be used control timing of the peak (and feeding). Adjusting the temperature of your starter can also change the time required to peak. Cooler starters peak more slowly than warm starters, but they are equally strong.
No. We tend to anthropomorphize our starters, but they do not have a stomach, fat stores or a brain, so it is impossible for them to be “hungry.” A starter does not eat faster or slower based on the prior feeding interval (at constant temperatures). They eat in the presence of food and do not eat if there is no food available.
In your starter culture are simply controlling a yeast population. Your population of yeast can grow in size, but an individual yeast cell never eats “faster or slower” (at a constant temperature) based on the prior feeding interval. It eats in the presence of food.
An individual cell can eat faster or slower only based on the temperature. Warmer yeast cells eat faster than colder cells.
If your yeast population has consumed all of the food and the starter has fallen and is covered with hooch, this means that the population has consumed all of the available food. In this case one could argue that the population is “starving” because it has no more available food. But when you feed this starter, individual yeast cells do not eat any faster or more vigorously than a recently fed starter. Individual yeast cells eat at a constant rate in the presence of food (at a constant temperature).
You can use a pH meter to get a estimate of the acidity of your starter, but the only true measurement of acidity is to measure Total Titratable Acid (TTA). This requires specialized equipment and is not usually practical to do it at home.
Here is a video from Karl De Smedt from the Sourdough Library demonstrating how to measure TTA.
videos
How to Strengthen a Weak, Acidic Sourdough Starter
Are you struggling with a sluggish, weak starter?
Most weak starters are actually acidicstarters. In this video, learn the science behind starter acidity and learn the tools and techniques to deacidify a weak, acidic starter. This video includes the Peak-to-Peak feeding method and other tips to get your starter in top shape.
Note: This video is for mature starters. If you are struggling with a new starter, check out my tools and tips here.
50 Ways to Kill Your Starter
“I think I killed my starter!” This humorous and fascinating educational video demonstrates all the common (and some uncommon) ways that people accidentally “kill” their starter. The video proves that it is exceptionally difficult to actually kill a sourdough starter and demonstrates many methods for saving a compromised starter.
Scroll through the chapters to view the different methods.
The BIGGEST MISTAKE You Can Make With Your Sourdough Starter: Premature Discarding
Can you kill your starter by using the wrong feeding method?
You can’t actually kill it, but many bakers mistakenly discard and refeed their starters so frequently that they weaken it to the point of near-death. Learn how to avoid this mistake.
Your starter is like a house plant. The bubbles are the leaves. If you don’t see bubbles, don’t prune (discard), water and feed it! Give it time.
How to Give a Bath to Your Sourdough, Puratos Group
How can I de-acidify my starter?
Karl De Smedt demonstrates how to de-acidify your sourdough starter.
I’ve also accomplished the same thing by mixing a dry mix in my starter jar (feed existing starter with flour only, no water until it is stiff). Then I fill my jar to the top with filtered water and let it sit on the countertop for about 30 minutes. I then pour off the water and give my (now very wet) starter a normal feeding.
Additional resources
Sourdough Starter Troubleshooting, True Sourdough – Here is a helpful post from Aysha at True Sourdough on how to troubleshoot starter issues.
21 Common Sourdough Starter Problems with Solutions, The Perfect Loaf – Here is a helpful post from Maurizio at The Perfect Loaf.
“This Bread Was Made Using4,500-Year-OldYeast,”Smithsonian– Here is a fascinating article demonstrating how difficult it is to kill your sourdough starter.
