Sourdough discard lasts up to 2 weeks in the fridge in a sealed jar at 3–5°C. It's still safe to use for longer — up to a month, sometimes more — but the flavour shifts from mildly tangy to sharply vinegary, which is welcome in crackers, pizza dough and savoury bakes but unpleasant in sweet ones. Pour off any clear hooch, look (and sniff) for the real spoilage signs below, and the rest of this guide tells you exactly when to use, when to bin.
The short answer
If you only read one line: sourdough discard keeps in the fridge for up to 2 weeks in a sealed glass jar, and stays usable for a month or so in savoury bakes if you're not seeing mould or pink streaks. Past a month, it's still occasionally fine — but you've got to look, sniff, and trust your nose more than your calendar.
How long can you keep sourdough discard?
Sourdough discard keeps for up to 2 weeks in the fridge in a sealed glass jar at 3–5°C, the safe UK fridge range. It stays edible for longer — often a month — but the flavour turns sharply vinegary, so use older discard only in savoury bakes like crackers, pizza dough or flatbreads. Always check for mould or pink streaks before using, regardless of age.
Why the fridge slows your discard but doesn't kill it
What's actually happening in there
Discard isn't dead. It's just slow. The wild yeasts and lactic acid bacteria that gave it life are still in there — they've just dropped their metabolism by about 90% in the cold. They still nibble at the flour, they still produce gas and acid, but at a rate slow enough that a fed batch on Monday morning will look much the same on Friday night.
What changes most over time is the balance of acids the bacteria produce. Fresh discard is dominated by lactic acid — the mild, yoghurt-like tang you taste in a young starter. As days pass in the fridge, the acetic acid bacteria keep working steadily while the lactic-acid producers slow down faster, and the acid balance tips. That's why old discard smells like vinegar.
Why temperature matters — UK fridges run 3–5°C
The Food Standards Agency says a UK fridge should run between 3 and 5°C. Most modern fridges hit this comfortably on the middle shelf. The back of the fridge often runs a degree or two colder, and the door — where most people put their jars — runs 2 to 3°C warmer. That difference matters: a jar stored in the door at 7°C will turn sharply vinegary in about 8 days; the same jar on the middle shelf at 4°C will hold its tang for two full weeks.
Store discard on the middle shelf, towards the back. Not the door.
Day-by-day: what to expect from your discard
Day 1 to Day 3 — sweet, gentle, almost any bake
In the first three days, discard tastes barely sour. It's milky, slightly sweet, with a soft yoghurt note. Use it in anything: pancakes, scones, brownies, banana bread, cake. This is the "no compromise" window.
Day 4 to Day 7 — tangy, the workhorse window
By day four, the tang has come up. It's recognisable as sourdough now — still pleasant, still balanced, but with personality. This is the sweet spot for crackers, soda breads, and the kind of bakes where you want a little sour. Sweet bakes still work; you might just notice the tang.
Week 2 — sharp and vinegary, savoury-only
Days 8 to 14 are the vinegary window. The discard smells acidic, like apple cider vinegar, with a stronger edge than the yoghurt smell of a young starter. It's safe and delicious — but only in savoury bakes. Pizza dough loves it. Flatbreads love it. Crackers thrive on it. Don't put it in a sponge cake.
Beyond Week 2 — still safe, but a different beast
After two weeks, discard often keeps going for another two or three. It's pure vinegar-tang now, sometimes with a faint boozy edge from the alcohols building up. It's not bad, but it's also not the same ingredient it was. We use month-old discard in dog biscuits, very long-cold-fermented pizza, and savoury crackers — and that's about it. Past about six weeks, we bin and start fresh.
Can I keep sourdough discard for a month?
Yes, sourdough discard kept refrigerated in a clean jar at 3–5°C is usually safe to bake with for up to a month, provided there are no signs of mould or pink/orange discoloration. The flavour will be aggressively vinegary, so use it only in savoury bakes — crackers, pizza dough, flatbreads, savoury scones. We wouldn't add month-old discard to pancakes or cake.
Flavour profile over 4 weeks
Based on The Sourdough Hub's own fridge logs from Clara's Somerset kitchen, plus published acetic-acid concentration curves in refrigerated discard. Your jar may run a day or two faster or slower depending on fridge temperature.
When discard becomes unusable (the real spoilage signs)
How do I know if my sourdough discard has gone bad?
Sourdough discard has gone bad when you see fuzzy mould (any colour), pink or orange streaks, or smell something that isn't sharp vinegar — rotting fruit, nail-polish solvent, or a meaty off-note. Clear or grey liquid (hooch) on top is normal and not a spoilage sign. Stir it back in or pour it off. When in doubt, bin it and start fresh from your starter.
Hooch is fine. Pink or orange streaks are not.
Hooch — the clear or greyish liquid that pools on top — is just water and alcohol the wild yeast produced. Pour it off, or stir it back in. Either is fine.
What is not fine is pink, orange, or red streaks in the discard. These are usually colonies of Serratia marcescens or Rhodotorula — they like the mildly acidic, mildly damp environment of a forgotten jar, and they can cause stomach upset. Pink discard goes in the bin, jar washed in hot soapy water, no exceptions.
Fuzzy mould — green, black, white, blue
Visible mould on the surface — fuzzy, raised, distinct from the discard itself — means bin. Don't try to scoop it off; mould threads run deeper than the surface fuzz you can see. Wash the jar in hot water, dry it, start a fresh discard jar from your next feed.
A smell that's "off", not just sharp
Discard should smell sharply tangy — vinegar at the older end, yoghurt at the younger. What it shouldn't smell like is rotting fruit, solvent (nail-polish-remover acetone), or anything meaty. A sharp acetic smell is normal. A weird smell isn't. Trust your nose.
Spoilage Check Wizard
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Is this discard safe?
Safe
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Storage tips that make discard last longer
The jar — glass, not plastic; loose lid, not airtight
Glass jam jars are perfect. Plastic absorbs smells and can hold residues that interfere with the discard. Choose a jar that's about half-full when you start — you want headspace for the discard to fizz and settle.
Does sourdough discard need to be in an airtight container?
Sourdough discard should not be stored in a fully airtight container. Fermentation continues slowly in the fridge and produces carbon dioxide; an airtight lid can build pressure and pop. Use a glass jar with a loose lid, a screw lid left a half-turn open, or cling film with a single pinhole. The jar should be clean, not sterile — wash hot and rinse.
Clara: "We cleaned discard off a kitchen ceiling once. The lid was on too tight. Lesson learned — half a turn, never more."
Labelling — date every jar
A bit of masking tape and a marker pen. Write the date you started the jar. That's it. No more "is this from last Tuesday or the Tuesday before?" guesswork.
Pouring off hooch (and when not to)
Pour off hooch if the discard is starting to look watery, or if you're about to use it in a thicker bake like crackers or biscuits. Stir it back in if you're making something where extra liquid doesn't matter (pancakes, batter bakes). Hooch isn't waste — it's just dilute alcohol and water.
What the FSA says about fermented dough storage
The Food Standards Agency's general guidance on chilled food in the home is straightforward: fridges should run between 3 and 5°C, chilled food should be eaten "by the use-by date" (which doesn't apply to home-made discard) or used within recommended windows. For fermented dough — discard included — the principle is the same: cold enough to slow microbial activity, monitored visually for spoilage, used within a sensible window.
For home-made sourdough discard, the sensible window the FSA implies (and that we follow at the Hub) is 2 weeks for any use, 4 weeks for savoury bakes only, with visual and smell checks every time.
Discard, food waste, and the UK angle
WRAP — the UK government-backed waste reduction body — estimates the average UK household bins around £1,000 of avoidable food a year. Sourdough discard is one of those quietly avoidable bits. A starter fed daily produces 100–400 g of discard a week. Over a year, that's 5–20 kg of flour and water passing through your fridge.
Knowing how long it keeps — and what each age window is good for — is a small but real lever against that waste.
Frequently asked questions
How long does sourdough discard last in the fridge?
Sourdough discard lasts up to 2 weeks in the fridge for any bake, and up to a month for savoury bakes only, provided you store it in a clean glass jar at 3–5°C and don't see any pink/orange streaks or fuzzy mould. The flavour shifts from mildly tangy to sharply vinegary as the weeks pass — fine in crackers and pizza dough, unpleasant in cake.
Can I freeze sourdough discard?
Yes. Sourdough discard freezes well for up to 3 months. Portion it into ice-cube trays (each cube is about 20 g), freeze, and bag the cubes once solid. Thaw a cube or two in the fridge overnight, or straight into a batter at room temperature. Frozen discard loses almost all leavening activity, but for flavour and structure it's identical.
What does spoiled sourdough discard look like?
Spoiled discard shows pink, orange, or red streaks (often Serratia marcescens contamination) or fuzzy mould — green, black, white, or blue — distinct from the discard itself. The smell is "off" rather than sharp: rotting fruit, nail-polish solvent, or anything meaty. Clear or grey liquid on top (hooch) is not spoilage — it's a normal by-product of fermentation.
Is hooch on sourdough discard safe?
Yes. Hooch is the clear or greyish liquid that pools on top of older discard. It's water and a small amount of alcohol the wild yeast produced when it ran out of food. Pour it off if you want a thicker discard, stir it back in if you don't mind extra liquid (pancakes, batter bakes). It's a sign of hungry, not bad.
Should I keep sourdough discard in an airtight jar?
No. Fermentation continues slowly in the cold and produces carbon dioxide; an airtight lid can build pressure and pop. Use a glass jar with a loose lid, a screw lid one half-turn open, or cling film with a single pinhole. The jar should be clean (hot soapy wash) but doesn't need to be sterilised.
Can old sourdough discard make you ill?
Old discard kept properly in the fridge — visible mould-free, no pink streaks, smell normal — is very unlikely to make you ill. The high acidity (pH 3.3–3.8) inhibits most pathogens. The risk comes from contamination signs you can see: pink/orange streaks (Serratia), fuzzy mould, or an off smell. If any of those are present, bin the discard, wash the jar in hot soapy water, and start fresh from your next starter feed.
What's next
Once you know how long discard keeps, the next question is usually what to do with it. We've got our roundup of 25 sourdough discard recipes for the big-picture answer, what you can actually do with discard for beginners, and discard pizza dough — the Friday-night fix for the most forgiving use of old discard there is.
