How to Feed and Maintain a Sourdough Starter

A sourdough starter is a living culture, and most problems with it come down to three things: how much you feed it, how warm it is and how long it waits between meals. This guide explains how to feed and maintain a sourdough starter, what the warning signs mean and how to adapt a routine written for cool kitchens to a hot one.

Our earlier article on sourdough bread chemistry and crumb structure followed a loaf from jar to cooling rack. This one stays with the jar. It is organised around the questions bakers actually ask once a starter exists: how often, how much, why it has stopped rising, and whether that odd layer on top is safe.

What feeding actually does

Each feed gives the culture fresh starch and sugars and dilutes the acid and alcohol that have built up since the last meal. The yeasts turn those sugars into carbon dioxide, which makes the starter rise; the lactic acid bacteria make lactic and acetic acids, which give sourdough its tang and keep the jar inhospitable to many unwanted microbes. Colorado State University Extension notes that this fermentation takes a well-kept starter’s pH safely below 4.6, the acidity that limits harmful microbes, including mould.

When the food runs out, the culture rises, peaks and then sinks back as the bubbles escape. Feeding before that point keeps the microbes active and the acidity in a healthy range. That is the whole logic of a schedule: match the gap between feeds to how quickly your culture eats.

Feeding ratios and hydration

The 1:1:1 starting point

King Arthur Baking’s maintenance method keeps 50 g of starter and feeds it 50 g of flour and 50 g of water, discarding the rest. That is a 1:1:1 ratio by weight, and it produces a starter at 100% hydration (equal weights of water and flour), the consistency of a thick batter. King Arthur recommends weighing rather than measuring by volume because a cup of starter can vary widely depending on how bubbly it is.

Bigger feeds for a slower rise

The ratio is a lever. Feeding a small amount of starter a larger amount of flour and water (for example 1:3:3 or 1:5:5) dilutes the culture more, so it takes longer to reach its peak. This is common practice among bakers in warm climates rather than a figure from a controlled study, so treat it as something to test: if your starter peaks and collapses long before you can use it, increase the ratio; if it barely moves, reduce it.

Thicker or thinner

Hydration changes behaviour too. A stiffer starter (less water than flour) generally ferments more slowly and holds its peak longer, while a runny one ferments faster. King Arthur’s troubleshooting guide is reassuring here: adding a little too much flour or water will not kill a starter, and you can correct the consistency at the next feed.

A feeding schedule you can adapt

Published schedules differ, partly because they assume different kitchens. King Arthur’s starter recipe calls for feeds about 12 hours apart while a new starter becomes established, and its sourdough guide advises feeding a room-temperature starter twice a day and a refrigerated one at least once a week. Its maintenance recipe, written for an established culture, describes a once-a-day routine and notes that a warmer kitchen means a faster rise and more frequent feeds. Use the table as a starting framework, then let your own jar tell you when it is hungry.

South Dakota State University Extension adds one rule worth keeping: do not put a brand-new starter in the fridge until it has established its microbiome, which takes about 7 to 10 days.

Temperature: why a hot kitchen changes everything

Most published guidance is written for temperate homes. King Arthur suggests an ideal of about 70–78 °F (roughly 21–26 °C) for a starter and warns that cold slows it down. SDSU Extension puts the sweet spot around 70 °F (21 °C) and cautions that higher temperatures can make fermentation so rapid that the starter may stop or spoil.

Microbiology explains why heat is not simply “faster”. In a widely cited 1998 study, Gänzle, Ehmann and Hammes measured growth of two typical sourdough organisms. The yeast (Candida milleri, now classified as Kazachstania humilis) grew fastest at 27 °C and showed no visible growth at 36 °C, while the lactic acid bacterium Lactobacillus sanfranciscensis had its optimum at 32–33 °C and kept growing well above the yeast’s limit, with no growth only at 41 °C.

In a hot kitchen the bacteria are in their element while the yeast is struggling, so a starter can become more sour and less lively at the same time.

That finding is from laboratory cultures, not a home jar, but it matches what many bakers in hot climates describe: in peak summer the starter peaks early, collapses, smells sharp and raises bread poorly. Approaches bakers commonly use (common practice to test, not tested claims) include:

• Feeding with cool or fridge-cold water to lower the starting temperature.
• Increasing the feeding ratio so the culture takes longer to run out of food.
• Keeping the starter slightly stiffer.
• Finding the coolest spot in the house, away from the stove and sunny walls, or keeping the jar in the fridge and only bringing it out to build up before a bake.

Avoid the opposite extreme as well. King Arthur notes that yeast dies at 140 °F (60 °C) and that a starter will suffer well below that, so never leave the jar near an oven, in direct sun or on top of a fridge’s warm exhaust.

Signs your starter is ready to use

King Arthur gives the clearest practical benchmark: a starter is ready when it roughly doubles within about 6–8 hours of a feed, is full of bubbles and smells pleasantly tangy rather than harsh. Practical checks:

• Rise: put a rubber band or a strip of tape at the level just after feeding, so you can see how far it climbs.
• Texture: domed, airy and webby when you pull a spoon through it, rather than flat and soupy.
• Smell: yeasty, mildly sour or faintly fruity. A strong nail-polish or vinegar smell usually means it is overdue for a feed.
• Timing: once it rises predictably by a similar amount in a similar time, it is stable.

Do not judge readiness by taste. Colorado State University Extension advises against tasting raw sourdough starter, because flour is a raw agricultural product rather than a ready-to-eat food; baking is the step that makes it safe.

Storing a starter in the fridge

The fridge is the simplest way to take a break from daily feeding. King Arthur’s routine is to feed the starter, let it sit at room temperature for 1 to 2 hours so fermentation gets going, then refrigerate it and repeat about once a week. Colorado State University Extension adds that refrigeration is optional if you feed regularly, and that unfed refrigerated starter may develop whitish clumps, which are yeast rather than mould.

Keep the jar loosely covered. Colorado State recommends a loose cover that keeps out airborne contaminants while letting fermentation gases escape; a screwed-down lid on an active starter can build pressure.

For longer breaks, the same Colorado State page notes that a starter can also be dried for long-term storage. A common home method is to spread a thin layer of active starter on baking paper, let it dry completely and store the flakes in an airtight jar; treat this as common practice and expect revival to take several feeds.

Reviving a neglected starter

King Arthur’s revival method is the same every time: discard all but 50 g, feed 50 g flour and 50 g water, and leave it at room temperature. It may bubble within a few hours or take up to 12 hours to show signs of life. Repeat every 12 hours until it doubles or triples within 6 to 8 hours.

Missed feeds are usually recoverable. King Arthur’s guide notes that a starter left in the fridge for months can probably be brought back, but it may take nearly as long as making a new starter. If it has been abandoned that long, check carefully for the warning signs below before you begin.

Troubleshooting: normal, fixable or throw it out

Hooch: liquid on top

A layer of liquid on a starter that has waited too long between feeds is called hooch. It is mostly water and alcohol from fermentation, and it signals hunger, not spoilage. King Arthur says that grey, brown and even black hooch do not indicate that the starter has spoiled, and Colorado State agrees that you can pour it off or stir it in. Pouring it off gives a slightly milder starter; frequent hooch is a cue to feed more often or use a larger ratio.

No rise after feeding

The usual causes are cold, a starter that is still too young, or a culture weakened by long neglect or heat. Work through them in order: move it somewhere warmer or cooler as needed, keep up twice-daily feeds for several days and make sure you are weighing. Changing flour can also slow a starter while the culture adjusts; wholegrain flours are commonly reported to ferment faster than refined ones.

Rises fast, then collapses and smells sharp

This is the classic hot-weather pattern described above. Increase the feeding ratio, use cool water, thicken it slightly, or move it to the fridge between bakes.

Mould, colours and smells that mean “discard”

This is the one situation with no rescue. SDSU Extension lists the signs of a starter that has gone bad as mould growing within and on top of the starter, a foul smell, and discoloration such as green, pink or orange spots. King Arthur describes mould as typically fuzzy and calls a pink or orange tint or streak a sure sign that the starter has gone bad.

Hygiene and handling

• Use a clean jar and spoon, and move the starter to a fresh jar every so often.
• Keep the jar loosely covered.
• Do not taste raw starter or dough.
• Do not pour discard straight down the sink or into the bin in liquid form. King Arthur suggests spreading it thinly on baking paper and letting it dry or baking it until brittle before throwing it away; better still, bake with it.

If you like this weigh-everything approach, our beginner’s guide to molecular gastronomy at home applies the same precision to gels and foams.

The bottom line

To feed and maintain a sourdough starter, start with equal weights of starter, flour and water, feed it on a rhythm that matches how fast it peaks, and use the fridge when you want a break. In a hot kitchen, slow it down with larger feeds, cool water and a cooler spot. Liquid on top means feed it; fuzz or pink and orange streaks mean start again. Keep notes for a few weeks and your starter will settle into a pattern you can plan your baking around.

Frequently asked questions

How often should I feed a sourdough starter?

At room temperature, King Arthur’s guidance ranges from once to twice a day; in a fridge, about once a week. In a hot kitchen it may need feeding more often or a larger ratio to avoid collapsing between feeds.

Can I use atta (Indian whole-wheat flour) to feed my starter?

Yes, any wheat flour will feed a starter, and wholegrain flours are commonly reported to ferment faster than refined flour. Switching flours can make the starter behave differently for a few feeds while the culture adjusts.

Why do I have to discard part of the starter?

Discarding keeps the jar a manageable size and lets each feed dilute the acid enough for the culture to stay active. Without it, you would need ever-larger feeds to keep the same ratio.

Is the grey liquid on my starter dangerous?

No. Hooch is a sign that the starter is hungry. Pour it off or stir it in and feed. Fuzzy mould, or pink, orange or green streaks, are different: discard the whole starter.

How long can a starter stay in the fridge without feeding?

Weekly feeding is the standard advice. A starter left for much longer can often be revived with repeated 12-hourly feeds, though King Arthur notes that after months it can take nearly as long as starting afresh.

Sources

1. Sourdough Starter, King Arthur Baking, accessed 2026.
2. Feeding and Maintaining Your Sourdough Starter, King Arthur Baking, accessed 2026.
3. Sourdough Baking: Maintain, King Arthur Baking, accessed 2026.
4. Sourdough starter troubleshooting, Barb Alpern, King Arthur Baking, 2018.
5. Sourdough Starter Best Practices, Colorado State University Extension (FoodSmart Colorado), reviewed 2025.
6. Sourdough Starters, Claudia Botzet, South Dakota State University Extension, updated 2024.
7. Modeling of Growth of Lactobacillus sanfranciscensis and Candida milleri in Response to Process Parameters of Sourdough Fermentation, M. G. Gänzle, M. Ehmann and W. P. Hammes, Applied and Environmental Microbiology, 1998.