I maintain a culture of flour, water, and microbes to generate the levain, an offspring so to speak, for mixing in with the main dough. It is a bit of an involved, triangular affair: me and the pair of wild yeast and friendly lactobacilli. And time and temperatures. And patience…

sourdough starter
Real sourdough is not made with commercial Baker’s yeast, but with long-fermented, ripe levain.

A strong, lively, mature, active, or ripe sourdough culture − whatever folks might call it − is the foundation of sourdough bread, that is, real sourdough bread. If the ingredients list on the bread package does not say sourdough starter, culture, or levain and perhaps only mentions yeast, it is not real sourdough bread.

The Perfect Loaf

In any case, let’s chat about references and instructional resources regarding sourdough starter, culture, and levain. Obviously, there are plenty of videos on YouTube. A few of them are by a fellow named Maurizio Leo who also has published a good book on baking and is a featured author on King Arthur’s website. He maintains his own blog called The Perfect Loaf and offers video instructions on YouTube. I got a lot out of his efforts and generally recommend his blog and videos wholeheartedly.

Lately, I came across a neat device, advocated for at The Perfect Loaf, that promises to reduce the frequency of having to feed a culture from once or twice a day. I got curious as the mounting discard from feeding the culture so frequently began to bug me.

The device, named the Sourdough Home, costs $99, probably worth every penny.



My following write-up is liberally adapted (plagiarized) from The Perfect Loaf. All credit to Maurizio Leo and other YouTubers like him for getting me going with baking sourdough bread. I wish not to try and reinvent the wheel.

My Fridge Is Cold

Sourdough is a living, breathing mix of wheat, water, beneficial wild yeast, and friendly bacteria. Its care requires a delicate balance of the right temperature, feeding schedule, and good flour to ensure the best baking results.

Chilling a culture is the best way to slow down its need for feedings. So when I do not bake for a while, I put my culture in the fridge. As a result, it’s always sluggish to ferment strongly when I pull it out and resume regular feeding. The cold temperatures of a home fridge (39°F/4°C) inhibit the fermentation activity of the bacteria and wild yeasts that make up a sourdough starter and culture.

After its cold slumber, I must give my culture at least a day, but usually several, of room temperature (or warmer) feedings to stimulate its usual fermentation power. If I try to use it earlier, it will only reluctantly ferment and leaven dough. The entire baking process requires more time, and usually, the resulting bread tastes flat with reduced flavor complexity.

The natural yeasts in sourdough starter are the most active between 75°F and 82°F. Anywhere outside that range and it’s much harder to get the culture to give us that beautiful ‘oven spring’ we’re looking for in our loaf of bread. After all, even humans get sluggish in environments that are too hot or too cold.

Controlling The Culture’s Temperature For A Leaner Feeding Schedule

With the reduced culture feeding schedules below, a baker can maintain a culture with the following ratios: 20% ripe carryover, 100% flour (perhaps 20% whole-grain rye and 80% white whole wheat flour), and 100% water (abbreviated with .2 / 1 / 1).

Because all of these schedules start with the same culture and ratios, one can change the temperature of the culture-keeping device (Sourdough Home or improvised DIY device) to determine how long it will rest there unattended.

Sourdough TemperatureTime Between Feedings
55°F (13°C)2 days
50°F (10°C)3 days
45°F (7°C)5 days

Schedule One: How to Feed A Culture Every Two Days

This is the shortest of the durations. Maurizio Leo at The Perfect Loaf recommends keeping a sourdough culture in the Sourdough Home at 55°F (13°C), then on Day 3 in the morning, separate some of the culture and give it a good feeding to let it become the levain for mixing a dough that afternoon. At the same time, he feeds the leftover or, better yet, carryover culture, puts it back in the Home for another couple of days and repeats the cycle. This temperature is cool, but not so cold that it drastically impacts the culture.

55°F (13°C)Day 1Day 2Day 3 (=> Day 1)
MorningCulture: feed
(.2 ripe starter/ 1 flour / 1 water) 3
Culture: no action– Make levain to mix that day 1
– Culture: feed and place it back in the Sourdough Home 2
EveningCulture: no actionCulture: no actionCulture: no action

Here is how it works for me

My 75% Whole Wheat Sourdough recipe calls for 360g of ripe levain, other recipes call for up to 20% of the weight of total dry flour.

Here is how the circle works as we enter on Day 3: on the morning of Day 3, my batch of culture should weigh at least 120g.

  1. To that batch of 120g culture, I add 130g of flour and 130g of water to yield a 380g batch. This batch, now called levain, needs to ferment for several hours until ripe.
  2. After this levain batch has fermented to ripeness, perhaps by the afternoon, I separate 360g to be used as actual levain and added to the bread dough, and retain the remaining 20g as carryover for culture. That 20g of carryover culture is fed that same afternoon by mixing in 100g of flour and 100g of water. Any leftovers are discarded.
  3. In effect, action point 2 constitutes the feeding of culture as outlined on Day 1. Any leftovers are discarded. There then is nothing to do the following Day 2.

Schedule Two: How to Feed A Culture Every Three Days

To further reduce culture feedings, Maurizio drops the temperature to 50°F (10°C). As in the schedule above, he feeds it as usual in the morning on Day 1, sets the Sourdough Home temperature, and forgets about it until the morning of Day 4.

50°F (10°C)Day 1Day 2Day 3Day 4 (=> Day 1)
Morning– Culture: feed
(.2 ripe starter/ 1 flour / 1 water)
Culture: no actionCulture: no action– Make levain to mix that day

– Culture: feed and place it back in the Sourdough Home
EveningCulture: no actionCulture: no actionCulture: no actionCulture: no action

Here is how it works for me

Same as Schedule One.

Schedule Three: How to Feed A Culture Every Five Days

Taking things even further, when the Sourdough Home is set to 45°F (7°C), he can stretch out the time between feedings. Still, even at a cool temperature, five days is a long time to go without refreshing a sourdough culture, and Maurizio sees it as the most stressful of all the schedules. It’s more stressful because it’s been so cold for so long, and in need of new food (flour) for metabolic activity.

45°F (7°C)Day 1Day 2Day 3Day 4Day 5Day 6 (=> Day 1)
MorningCulture: feed
(.2 ripe starter/ 1 flour / 1 water)
Culture: no actionCulture: no actionCulture: no actionCulture: no action– Make levain to mix that day

– Culture: and place it back in the Sourdough Home
EveningCulture: no actionCulture: no actionCulture: no actionCulture: no actionCulture: no actionCulture: no action

Maurizio found that when he made a levain from this colder starter, it took his levain 30 minutes longer than usual to ripen. Be sure to adjust the levain mixing water (by warming it) to compensate or give it a little more time before mixing the levain into the dough. As always, a baker wants the levain to have risen in the jar, be bubbly on the sides and top, and have a sour aroma with a loose consistency.

Here is how it works for me

Same as Schedule One.

An Example Schedule to Bake Once a Week

Let’s say a baker wants fresh bread for Sunday dinner, but also wants to minimize sourdough culture feedings (and attention!) during the week. This is the schedule and settings for the Sourdough Home that Maurizio recommends using to make it happen.

When transitioning to this schedule, the best way to begin is to feed a culture and put it into the Sourdough Home at 45°F (7°C) the day one wants to bake in the future. 

For example, if one wants to prepare the dough on Saturday for baking on Sunday, as shown in the chart below, make a levain and mix the dough as usual, then place it into the Sourdough Home at 45°F (7°C). Then, follow the actions listed in the chart to maintain it and make a levain every Saturday.

MorningBake loaves (in the morning, afternoon, or evening)
– Culture: no action
Culture: no actionCulture: no actionCulture: feed and put in SDH at 55°F (13°C)Culture: no action– Make levain
Culture: feed and put in SDH at 45°F (7°C)
Bake loaves (in morning, afternoon, or evening)
– Culture: no action
EveningCulture: no actionCulture: no actionCulture: no actionCulture: no actionCulture: no action– Mix dough, retard overnight
– Culture: No action
Culture: no action

Here is how it works for me

Similar to Schedule One.

Apropos Temps –
How Warm Should Final Dough Be At The Start Of And During Bulk Fermentation?


The warmer a sourdough bread dough, the faster it will ferment and rise. A dough should be warm enough to encourage lively fermentation and flavor creation but not be so warm that it quickly overproofs. For most recipes, bakers target a final dough temperature between 75° F to 78° F (24 to 25° C).

Bacteria and yeasts function optimally at different temperatures: 89°F (32°C) and 80°F (27°C), respectively. However, these temperatures are relatively high, so finding a happy medium accommodating both yeast and bacteria at around 78°F (25°C) results in a dough that’s warm enough to have ample bacteria and yeast fermentation activity but not so warm that one ends up with a dough that ferments too quickly and becomes sticky, hard to handle, and overproofs.

Whole grain doughs have increased bran and germ particles in the flour, which increases fermentation activity. Maurizio typically reduces the desired dough temperature (DDT) to around 75°F (23°C) for these doughs to avoid overproofing.

My Simple DIY Sourdough Culture Retarder

Igloo Mini Playmate

I am on a budget. So, how did I get started with a DIY culture retarder? I thought of a small travel cooler, only big enough for my Weck 3/4 quart starter jar, and with a couplezen ice packs in it, to keep my culture on a 20g/100g/100g ratio cool enough for only one feeding per day.

  • When it is too cold in the house, I store the starter in the kitchen oven with the oven light on to keep temperatures warm enough for the necessary fermentation to proceed, if ever so slowly, and requiring only one feeding per day.
  • When it is too warm in the house, I store my starter in this simple DIY starter cooler to keep the culture’s temperatures cool enough for the necessary fermentation to proceed, if ever so slowly, requiring only one daily feeding. Even with A/C on in the house, I must change the ice packs twice daily in Summer.

Yes, it is a hassle. Worse, with this simple DIY sourdough culture retarder, I cannot dial in the temperature of my starter to precisely what I want it to be so as to maximize bacteria and yeast activity) and thus have my culture ripe when I want for sure.

My best days are in the past. Eventually, I might break my piggy bank and instead get the Sourdough Home from Brød & Taylor, perhaps sooner than later.

My Complex DIY Sourdough Culture Retarder

On the other hand, my new idea for a DIY sourdough culture retarder is a small travel cooler that is thermoregulated with a Peltier cooler kit to create a proper environment for the culture to grow and thrive. I mean, that is what the Brød & Taylor device really is.

Even a DIY sourdough culture retarder can be cooled to a temperature that is not cold. With the ability to keep the cooler at low temps, but not at temps as cold as a typical home fridge at 39°F (4°C), a baker can get the sourdough culture to maintain high yeast and bacterial activity without getting so warm that the culture requires feedings once or twice a day.

Here’s a YouTube video of how to build something like my DIY sourdough culture retarder:


Building such a complex DIY sourdough culture retarder is kind of involved, and perhaps not much cheaper either. Hardcore tinkerers can get some inspiration from the following sites:


Amazingly, there is perhaps even no need for a DIY device. Why not just buy a cheap, off-the-shelf Peltier mini cooler? One of these might do the job as well:


That’s all for now, folks…


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