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Fermented Vegetables & Fruit

Fermented Spinach Recipe: How to Ferment Spinach and What It Changes

By Updated 2 min read

At a glance

You can ferment spinach like sauerkraut: massage it with 2% salt by weight, pack it under its own juice (top up with 2% brine) and leave it at 18–22°C for 3–7 days until clearly sour, then refrigerate. In a lab study, fermenting spinach powder with Lactiplantibacillus plantarum cut oxalates. Spinach is high in nitrate, which can turn into nitrite during fermentation, so don't give fermented spinach to babies.

  • Ferment spinach with 2% salt by weight for 3–7 days at 18–22°C.
  • Lab fermentation of spinach powder with L. plantarum lowered oxalates, phytates and glucosinolates.
  • Spinach is high in nitrate; fermentation can produce nitrite – meat processors use fermented spinach as a nitrite source.
  • Infants are most at risk from nitrite; don't feed fermented spinach to babies.
  • Nitrite in fermented vegetables falls as the brine becomes more acidic – eat it once clearly sour.

Ferment profile

Fermentation
Lactic acid
Main microbes
Lactic acid bacteria from the leaves (e.g. Lactiplantibacillus plantarum, Leuconostoc)
Live cultures
Yes
Alcohol
None / trace

Yes, you can ferment spinach. Like cabbage, spinach carries its own lactic acid bacteria; salt it, pack it under its own juice (or a little brine) and it sours in a few days into a soft, tangy, savory green. It’s more delicate than sauerkraut – the leaves collapse quickly – so it works best as a condiment, stirred into grain bowls, eggs, dips or soups, or mixed with sturdier vegetables. The recipe card below uses 2% salt by weight.

What Fermentation Does to Spinach

Spinach is famous for oxalates, which bind calcium and matter for people prone to kidney stones. In a 2023 study, researchers fermented spinach powder from three growth stages with Lactiplantibacillus plantarum: oxalates, phytates, alkaloids and glucosinolates all fell sharply, protein and fiber rose slightly as a share of the powder, and total phenolics and antioxidant activity didn’t change (Naseem et al., 2023). That was a controlled lab fermentation of dried powder, not a jar of salted leaves, so treat it as a sign of direction rather than a number for your batch – and if you’ve been told to limit oxalates, ask your doctor rather than relying on fermentation.

The Real Issue: Nitrate and Nitrite

Spinach can be very high in nitrate. The concern is nitrite: bacteria and the plant’s own enzymes can turn it into nitrite during storage and processing, and nitrite can cause methemoglobinemia (“blue baby” syndrome) – infants under 3 months are most at risk, older babies and children somewhat less so (Chan, 2011). Fermentation can make a lot of nitrite: meat processors use fermented spinach as a natural “pre-converted nitrite” source for curing pork (Kim et al., 2017).

In fermented vegetables, nitrite tends to peak early and then falls as the brine gets more acidic – in one study of Chinese fermented cabbage brine, from 32 mg/kg at pH 4.7 to almost nothing at pH 3.6 (Xu et al., 2024). So:

  • Don’t give fermented spinach (or its brine) to babies or toddlers.
  • Let it ferment until it’s clearly sour – don’t eat it in the first couple of days.
  • Eat it as a condiment, in small portions, as part of a varied diet.

Is Fermented Spinach Good for You?

Eaten raw after fermentation, it contains live lactic acid bacteria, and spinach brings vitamin K, folate and carotenoids. There are no human studies of fermented spinach itself, so “benefits” claims beyond that are guesswork. Vitamin K matters if you take warfarin – keep your intake of leafy greens steady and talk to your doctor before changing it. For more fermented greens, see Nepal’s gundruk; for the basics of salt and vegetables, our sauerkraut recipe and troubleshooting guide.

Recipe: Fermented Spinach (2% Salt)

Makes
About a 500 ml jar
Hands-on
20 min
Fermentation
3–7 days at 18–22°C
Salt
2% of the spinach weight (10 g per 500 g); top-up brine 20 g salt per litre
Temperature
18–22°C (64–72°F)
Difficulty
Easy

Equipment

  • Scale
  • Large bowl
  • 500 ml jar
  • Small weight
  • Lid or airlock

Ingredients

  • 500 g fresh spinach (thick stems removed, roughly chopped)
  • 10 g salt (2% of the spinach weight)
  • 1–2 garlic cloves, sliced (optional)
  • As needed 2% brine (20 g salt per litre of water) (if the spinach doesn't cover itself)

Method

  1. Wash and drain the spinach, remove thick stems, and chop roughly. Weigh it.
  2. Toss with 2% of its weight in salt and squeeze firmly for a few minutes until it collapses and releases juice. Mix in the garlic.
  3. Pack tightly into the jar and press under its own juice; top up with 2% brine if needed so everything is submerged. Weigh down.
  4. Close loosely (or fit an airlock) and keep at 18–22°C, pressing the leaves under daily.
  5. Taste from day 3; when clearly sour (usually 3–7 days), close the jar and refrigerate. Eat within a few weeks.
  6. Discard if it turns slimy or grows fuzzy colored mold. Don't give it to babies or toddlers.

Frequently asked questions

Can you ferment spinach?

Yes. Salt it at about 2% by weight, pack it under its own juice and leave it at room temperature for 3–7 days until sour. It goes soft, so it's best as a condiment.

Does fermenting spinach reduce oxalates?

In a lab study, fermenting spinach powder with Lactiplantibacillus plantarum lowered oxalates substantially. Home results will vary; if you need a low-oxalate diet, ask your doctor.

Is fermented spinach safe?

For adults, made with enough salt and eaten once fully sour, yes. Because spinach is high in nitrate, which fermentation can turn into nitrite, don't give it to babies or toddlers.

What are the benefits of fermented spinach?

Raw fermented spinach contains live lactic acid bacteria plus spinach's vitamin K, folate and carotenoids. There are no human studies of fermented spinach itself.

How long does fermented spinach take?

About 3–7 days at 18–22°C, until it tastes clearly sour; then refrigerate it.

Can I ferment spinach with other vegetables?

Yes – mixing it with cabbage, carrots or radish gives a sturdier texture. Use 2% salt by the total weight.

Sources

  1. Naseem A et al. (2023). Effect of growth stages and lactic acid fermentation on anti-nutrients and nutritional attributes of spinach (Spinacia oleracea). Microorganisms 11(9):2343. Link
  2. Chan TY (2011). Vegetable-borne nitrate and nitrite and the risk of methaemoglobinaemia. Toxicol Lett 200(1–2):107–108. Link
  3. Kim TK et al. (2017). Effect of fermented spinach as sources of pre-converted nitrite on color development of cured pork loin. Korean J Food Sci Anim Resour 37(1):105–113. Link
  4. Xu X et al. (2024). Analysis of microbial diversity dominating nitrite enzymatic degradation and acidic degradation in the fermentation broth of Northeast sauerkraut. Foods 13(24):4168. Link
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