I have experienced a sourdough starter with Serraita marcescens and I can tell you I did salvage my starter and am still baking all sorts of sourdough goodies with it today.
What is it Serratia Marcescens?
Serratia Marcescens is an opportunistic pathogen that can survive in many locations that you would think are clean and germ-free. It is known for its recognisable pink or reddish hues.
“Serratia Marcescens can utilize a wide range of nutrients, which aids its ability to survive and grow under extreme conditions, including in the presence of disinfectants and antiseptics”
Serratia Marcescens can be found in dairy, fish, meat and soy products, outbreaks have occurred in hospitals from wet areas infecting sick patients, and in baby milk bottles in neonatal units, It is not something you want in your home.
However, we all have Serratia Marcesens in our guts, but in healthy individuals, it is outnumbered by good bacteria and therefore, isn’t harmful.
With this knowledge, you can begin to understand what is going on in your sourdough starter, as all sourdough starters are a colony of bacteria and wild yeasts, giving off gases (carbon dioxide) that create gas bubbles that make your bread rise.
So if you open your sourdough starter one day and find the pink hues of Serratia Marcescens never fear, you can save your sourdough starter.
How did Serratia Marcescens get into my sourdough starter?
the sourdough starter you keep on the bench is a colony of bacteria and wild yeasts. When you feed it with water and flour you are keeping it fed, which means the bacteria in the starter can digest the fresh glutens and proteins in the flour.
if you neglect this then the bacteria begins to die, and the stronger bacteria begin to eat the weaker bacteria. When this happens for long enough you are left with a jar full of the nasty by-products of the now overwhelming number of bad bacteria.
This can be mould, a rotten smell, or Serratia Marcescens.
The bacteria were always in your sourdough starter, including Serratia Marcescens, but they have taken over because you neglected to feed the colony.
This doesn’t make your sourdough dead, or unsalvagable it is a living colony.
You need to salvage a little. feed it daily or twice daily until those good bacteria once again outnumber the bad.
Things to consider before saving a sourdough starter with suspected Serratia Marcescens.
- The presence of Serratia Marcescens shouldn’t be something you have occurring often. If it is you may have more than the usual amount of this bacteria in your home.
Remember, this bacteria is hard to kill and can be found in wet places especially.
Sourdough starter is created by taking the wild yeasts from the air in your home, this will include bacteria in the air in your hands are you handle the dough of your breads.
this isn’t a and thing, in fact, the more you leave your sourdough in the air to handle it, the more is customised to you and your family.
but if you feed your sourdough often, and still struggle with mould or the pink streaks of Serratia Marcescens, then you should check your bathrooms, kitchen and laundry for pink mould.
2. if you have someone in your home who has digestive issues, linked with a weak gut lining, struggles with wound healing or is taking immune suppressants, then I would consider not saving the sourdough, or at least making sure they don’t eat any until it is healthy and smells like yogurt.
in the scientific article I link at the bottom of this post, there were cases of people with infections, catheters, open wounds and other ailments in hospitals, who became sick with the bacteria Serratia Marcescens, while this is few and far between, and doesn’t occur in healthy children and adults if you have someone suffering from those things in your home, then remove the sourdough starter.
Will my sourdough be safe after saving it from Serratia Marcescens?
The answer is yes.
you had a colony of wild yeasts and bacteria on your benchtop. It always contained bad bacteria.
If you neglected your sourdough (we all do at some point) the bad bacteria took over, and now you need to balance that with the good bacteria. All they need is regular feedings and time to come back in the high numbers you need for a healthy sourdough starter.
Serratia Marcescens will die at anything over 62 degrees Celsius (143 f) so even IF you had a little to much in your sourdough starter, the baking process will kill it.
What to do to save your sourdough starter from Serratia Marcescens (pink streaks)
if you have a large or a small jar of sourdough starter it doesn’t matter.
- save what you can, trying to avoid getting any of the pink streaks in the starter you are saving, anywhere from a tablespoon to half a cup.
- discard the rest and wash the jar and lid thoroughly.
- in a new or the same jar, add the sourdough you saved and feed it, you may need to weigh how much starter you saved and add the same weight in flour and water. (always use filtered water, or water that has been sitting for 24 hours.)
- repeat this, discarding when you have enough, until your sourdough smells like yogurt, and is bubbly and rising after each feeding.
- you may need to feed once or twice a day, depending on the temperature of your kitchen, a hotter kitchen starter usually requires more feedings.
- for my starter it took 7 days, it may take longer or shorter for yours.
- it can depend on the overall health and age of your sourdough starter.
when your sourdough is bubbly, smells good and is rising, start baking with it again!
this is the load I made one week later!
here is the website I quoted at the top of the post where you can read much more in-depth and scientifically about Serratia Marcescens.