If you didn't discard a portion of your starter each time you feed it, two things would happen: Your starter would grow to an enormous, unmanageable size. Your starter would likely become more and more inhospitable to the bacteria and yeast we want as the mixture would become ever more acidic.
If your recipe calls for more than 227g (about 1 cup) of starter, feed it without discarding until you've reached the amount you need (plus 113g to keep and feed again).
Sourdough starters require regular feedings to stay active. If you don't discard the excess, eventually you'll have more starter than your feedings can sustain.
Feeding sourdough starter
You can leave the starter in the refrigerator for 3 to 4 days at a time between feedings. We recommend feeding sourdough starter at least twice a week for best results.
If it smells yeasty and not too sharp, if the color is still pale ivory (and not brown or pink), then it's probably fine. The rule of any kitchen is “When in doubt, throw it out,” but I wouldn't panic and toss your starter if you only missed 1-3 days of feeding.
Warmer homes or frequent baking will require more frequent feeding (around every 12 hours), while colder homes every 24 hours. Storing your sourdough starter in the fridge will require feeding around once a week. It can, however, be stored up to two months in the fridge without being fed.
The beneficial bacteria and yeast in the starter create acidic conditions that help to naturally preserve it and ward off mold. That's not to say an old neglected sourdough starter doesn't look and smell pretty funky though! But more often than not, it's still alive and okay to use.
If not fed regularly with fresh water and flour, the natural yeast within the starter will run out of food and ultimately die.
Things that WILL kill your sourdough starter
It's best to maintain your starter at comfortable room temperature (around 70°F), though a little higher or lower won't hurt anything. SEVERE NEGLECT: If you neglect your starter long enough, it will develop mold or signs of being overtaken by bad bacteria.
It's also sign that your sourdough starter is hungry. Pour as much of the hooch as you can off the top, then stir your starter before feeding it.
The best way to tell if your sourdough starter is dead is if it does not respond to regular feedings. When you add fresh flour and water to the mix, you should see it come back to life through bubbling. Feeding it means adding fresh flour and water to keep the beneficial bacteria and yeast alive.
What Does Bad Sourdough Starter Look Like? It's usually pretty obvious when your starter has gone bad. You will either see mold or discoloration (generally pink or orange). If you see either of these things, you will need to toss your starter.
Going a week or so without feeding your sourdough starter while it's in the fridge should not cause mold in a healthy starter. However, leaving a starter on the counter for a week or two with no feedings will likely result in a bad sourdough starter.
Let your starter rest at warm room temperature for 12 hours
Your starter will wake up more quickly than it might have. Despite showing absolutely no activity at all after its first feeding (and 12-hour rest), once I gave the starter a second feeding it just about doubled within 5 hours.
A mature sourdough starter will reach its peak around 2 to 4 hours after being fed. If it's particularly cold, or you've given it a huge feeding ratio, this could be extended to 12 hours.
The very short answer is, your sourdough starter generally will be at its peak anything between 4 and 12 hours after feeding. The optimum time to use it will be when there are lots of bubbles at its surface and it has has physically risen to its peak level, just before deflating back down again.
The oldest known sourdough starter is said to have originated from clay pots unearthed in Egypt. Seamus Blackley baked a loaf of sourdough bread using yeast harvested from 4500 year old clay pots. If you want to read more about this 4500 year old sourdough starter, go here.
If a sourdough starter is not bubbly, it may require more frequent feedings. If feeding every 12 hours, increase to feeding every 8-10 hours, to make sure the culture is getting enough food. Check the temperature in the culturing area. Sourdough likes a temperature between 70°F and 85ºF, around the clock.
My Sourdough Starter is Not Sour Enough
This usually happens if your starter isn't as active or if you use it when it isn't mature enough.
With an aggressive feeding schedule (2-3 times daily), you should begin to see bubbling and sour notes by day three (and is a good indicator for collecting the Lactobacillus bacteria). By Day 5, I typically give up if there's no rise or sour notes. There's two common factors that make sourdough fermentation difficult.
And even if you are on top of the maintenance, sometimes a starter turns sluggish simply for reasons unknown. Fortunately, bringing an ailing sourdough starter back to life is simple: You just give it a lot of nutrients by feeding it frequently.
Some other signs your sourdough starter is being overfed are: sourdough starter not bubbling or rising. not smelling yeasty. starter is runny.
First, take it out of the fridge and let it come to room temperature. Then, feed it with equal parts flour and water (by weight) and let it sit at room temperature for a few hours. After that, it should be ready to use in your baking!
It is important to continue feeding the starter at room temperature until it is reliably bubbly a few hours after feeding, for 3 consecutive feedings. Getting to that point can take 3 to 7 days of feeding the starter every 12 to 24 hours (every 2 to 4 hours for our Gluten-free Sourdough Starter).