starter getting sour with no power!

Greetings

14 days ago, I began making a new yogurt starter with 40g yogurt + 40g ww flour) in very warm temp, around 95f (I kept the jar on the mesh behind the fridge). By day 3 it expanded 4x, probably due to Leuconostoc bacteria. Then I moved it on the counter. Room temp at my end is around 85-90. It stopped expanding for a day, then yeast began to show up little by little. By day 7 I could smell yeast and it expanded 3x in 10 hours. All that time it was a stiff starter. I began switching to 100% hydration because its easier to mix. The following days yeast showed less presence, and it took longer to peak. Now my starter hardly peaks, and all sour, but no power. I tested it twice to make a dough, but it turned our flat with no rise.

What did I do wrong? why is the Lactobacilli taking over? was it the 100% hydration that caused the disappearance of yeast power?

How do I develop yeast power in my starter? should I make it stiffer again? should I retard it in the fridge? its been 14 days now..

I've found very important info from this comment made by Debra Wink. She says:

" type II sourdoughs, maintained at a high temperature (>85F) with low refreshment rate and long ripening time. Yeast don't do well in that environment because of the temperature, nor does Lactobacillus sanfranciscensis because of the low pH. Cultures maintained this way get very sour and lose their yeast. They are used for flavoring but not for leavening."

She also said:

"Even though you are using a relatively low refreshemnt rate, the low temperature creates the opposite effect on your starter. Lactobacilli slow way down; and yeast slow down too, but not as much. Because the lactobacilli slow down and don't divide as quickly, the population shrinks in relation to the yeast. And acids don't accumulate vary fast, because 1) there are less bacteria to make them, and 2) the bacteria that are there are producing the acids more slowly. At the same time the yeasts have less competition from bacteria for sugars, and less acetic acid to contend with, so they have a tendency to do fairly well. For this reason I think you'll find that starters maintained cool get less sour and rise quite well between refreshments."

So, could the fix for my starter is to make it stiffer and retard it in the fridge for some time to develop yeast power?

would be to feed more flour or make it thicker. and get the temperature down into the upper 70's°F for more yeast growth. As the temperature drops below 70°F the yeast slow down dramatically with each degree practically stopping with refrigerator temps of 38°F.

I agree with Debra Wink. Good job finding this quote. :)

When the yeast show up in a new starter, the starter will need to be fed more often. Combine with heat, the starter will do as yours did unless it is fed more. With thick or thin starters wait for the freshly fed starter to start rising and showing signs of life, then refrigerate to slow everything down. Refrigerator temps can be very cold. Too cold to grow yeast quickly. I would build yeast around 76°F for a few feeds then transfer the starter to the refrigerator several hours after the last feeding.

Going from a thick starter to a thin one more than likely sped up fermentation. Thinner starters also don't rise as high as their thicker counterparts as they don't have the strength to hold themselves up. Generally speaking, without the use of a refrigerator, thick starters are more easily maintained in warm climates and thin ones in cold climates.

But how do I get the temperature down into the upper 70's°F? My room temp is in the upper 80's..

There must be a way. You might try to put the starter in and out of the refrigerator to lower it or feed initially with cool water. Wrap it with a damp cloth to keep cool or set the starter inside a porous wet (but fired) clay pot. or insulate it against the cold in the refrigerator, perhaps inside a small box or second jar to minimize temperature swings.

Excellent ideas! many thanks.

put it into the fridge to cool it down for the rest of the day. Do this a few times to build the yeast. Then switch to feeding , waiting a few hours and then chilling the starter for maintenance. You only have to keep the starter coolish for this initial growth period (or whenever it starts acting sluggish and sour.)

Based on your tips, here is what I'll do, please correct me if I got it wrong:

I've put the jar in a pan of water in the fridge for 15 minutes, then covered in room temp. When it peaks I'll put the jar in the fridge for the rest of the day, then take it out the next morning, feed it, wait until it peaks then put it back in the fridge for the next day, and repeat a few times.

Is that right?

:) Maybe drop an ice cube in the outside pan of water if it gets too warm.

Unless you have the scales to measure small amounts this can be tricky to add salt to the starter. Might be easier to add it to the flour first, the flour you feed your starter for maintenance. If I remember right, start out feeding 3% salt (on the flour amount.) You can raise it to 4% later on if you find 3% too low. Be sure to make adjustments in the recipe salt.

Split the starter you have into three or four parts and try different things at the same time to find out what works best. Save a sample in the refrigerator just in case as a "back up."

I've increased the thickness of the starter. This worked wonders.. 3x rise in 9 hours.

The question now, how do I tell when a stiff starter peaks? if the dome went down? here is a pic of the starter now:

and you will see more bubbles thru the glass on the sides of the starter. I don't think it's there yet.

Have you got your recipe handy? Keep it coolish and not too warm. :)

How much starter, water and flour did you use?

No recipe yet. I am still developing the new starter, in hope that yeast shows up.

Before the last feed, it was 20g starter, 30g flour, 30g water. When 12 hours passed with no noticeable activity, I added 30g flour to thicken it, without discarding.