Fridge storage, dormancy, and bringing it back

A sourdough starter is alive, but it doesn't have to live at your daily attention. Most home bakers (anyone who isn't baking every single day) keep their starter in the fridge between bakes. The cold dramatically slows the microbes, which means you can go a week or two between feedings without harm. With more care, a starter can survive months of dormancy.

The mechanics are simple. The judgement is in knowing when to refresh and how to bring it back.

Why fridge storage works

Fridge temperature (typically 4 °C / 40 °F) is well below the comfort zone for sourdough microbes. The yeast slows almost to a halt. The bacteria slow down too, but less. They keep producing acid at a low rate even at fridge temperatures.

By the Q10 rule from the Foundations article, fridge temperature is roughly 1/8th the speed of warm room temperature for the yeast. What would peak in 8 hours at 24 °C / 75 °F takes about 2.5 days at 4 °C / 40 °F. The acid keeps building, but the gas production largely pauses.

The standard fridge routine

If you bake roughly once a week:

1. 1.Day before fridge: Feed the starter as normal at a 1:5:5 ratio. Wait about 2 hours at room temperature so the microbes start working.
2. 2.Into the fridge: Cap loosely (some gas will still be produced) and put it on a middle shelf. Avoid the door; temperature swings every time you open it.
3. 3.Day before bake: Pull from the fridge. The starter will look hungry: flat surface, possibly some hooch on top. This is normal.
4. 4.Refresh feeding: Discard down to a small amount, feed at 1:5:5, leave at room temperature.
5. 5.Watch for peak: Most starters need 2–3 feedings spaced 12 hours apart at room temperature to fully wake up. The first feeding after fridge often peaks late and weakly. The second feeding is usually back to normal timing. The third confirms it's ready.

Don't bake with the first post-fridge feeding. The yeast is still groggy. The second or third feeding is when the starter is back to full power.

How long can a starter sit in the fridge?

With one feeding before storage, a starter is comfortable in the fridge for 1–2 weeks. Past two weeks, hooch will accumulate, the smell will sharpen, and the wake-up will take more feedings. Past four weeks, the wake-up gets harder.

But even badly neglected starters are usually rescuable. Sourdough cultures are stubborn. The yeast and bacteria can persist for months in a hungry, acidic state: slowed almost to dormancy, but not dead.

Reviving a long-neglected starter

If you find a starter that's been in the fridge for 6 weeks, 6 months, or longer:

1. 1.Inspect. Pour off any hooch. Look for mould: pink, orange, or fuzzy white-on-white growth means throw it out and start fresh. Greyish-brown hooch and a strong sour smell are normal and not a problem.
2. 2.Take a small amount. A spoonful, no more, about 20 g. This is your seed.
3. 3.Feed at high ratio. Combine the 20 g of seed with 100 g flour and 100 g water (1:5:5). Stir well. Leave at warm room temperature (24–26 °C / 75–79 °F if possible).
4. 4.Repeat for several days. Twice-daily feedings at 1:5:5 for 3–5 days. The first feedings will be sluggish, barely any rise. By feeding 4 or 5 you should see normal activity returning.
5. 5.Confirm with two reliable peaks. Once two consecutive feedings peak in their normal time window, the starter is back.

If after a week of consistent twice-daily feedings the starter still isn't peaking reliably, the original culture probably didn't survive. Build a fresh one; it takes less time than fighting a dead culture.

Going on vacation

For trips of 1–2 weeks, the standard fridge routine is fine. Feed at high ratio (1:5:5 or 1:10:10) the day before you leave, leave it at room temperature for a couple of hours, then into the fridge. Wake it up when you get back.

For trips longer than two weeks, you have three options.

• Ask a friend to feed it. Once a week with a 1:5:5 ratio is enough. They don't need to be a baker; give them written instructions.
• Dry it. Spread a thin layer of fed starter on parchment paper, let it dry at room temperature for 1–2 days until brittle. Crumble into flakes and store in a sealed container. Dried starter keeps for years. Reactivate by mixing with water and feeding daily for 3–5 days.
• Freeze it. Less reliable than drying but quicker. Freeze a small amount of fed starter in a sealed container. Thaw at room temperature and feed for several days to revive. Freezing kills some of the population, so the wake-up is slower than from dried.

Drying is the most robust option for travelling bakers. A small jar of dried starter flakes is your insurance policy. If anything ever goes wrong with your live culture, you can rebuild from the dried version in a week.

What 'never feed' means

There is no schedule that requires daily feedings forever. Many serious home bakers feed their starters once a week, with one or two refresh feedings before a bake. The "feed every 12 hours or it dies" advice you'll see online is either over-cautious or written for a specific kind of starter (very young, or stiff *lievito madre* used for panettone).

A mature starter is hard to kill. Treat it well, but don't let the maintenance dictate your life.

The takeaway

A weekly baker keeps a starter in the fridge between bakes, refreshes twice before baking, and never thinks about it on the days they're not baking. A monthly baker dries a portion as backup. A traveling baker brings the dried flakes along. The starter doesn't run your life unless you let it.