It was in the autumn of 2019, when I walked past wild olive trees at the foot of Mount Olympus and picked a few of the firm, green fruits here and there. Ferment olives, the idea was there at once! Unfortunately, there weren't enough wild olive trees to harvest a respectable amount of olives for this endeavor, so a few days later I went to the Κεντρική Δημοτική Αγορά Αθήνας, the central market in Athens, filled up the kilo and took it all back to northern Germany as a fresh, fermentable souvenir.

In their raw state, olives are horribly bitter and toxic due to the presence of the compound oleuropein. Before olives can be eaten, they are always cured to reduce oleuropein.

Sandor Ellix Katz, The Art of Fermentation

Curing, of course fermenting, but how? I had to figure out the way to do it. The most important thing in processing fresh olives, leaching the oleuropein compound, can be achieved in several ways. The most common methods to debitter and ripen olives are with brine, dry salt, water or lye.

Fermenting olives

In industrial production, the olives are soaked in sodium hydroxide solution. Of course, you can do this at home, it's fast and efficient - but that's not what I'm about, I'd rather ferment the fruit. Olives, in fact, contain many valuable nutrients that are preserved by the natural ripening process of fermentation, while at the same time debittering and preserving the fruit.

Harvest olives

If you don't live in a country where olives grow and you can either harvest them yourself or just buy them at the market, you can ask your greengrocer to bring you a box from the wholesale market. My local vegetable dealer is happy to do this for me, so that I can ferment olives myself every year. A box of 4-5 kg is just about enough for our annual consumption.

Green or black olives?

The color of the fruit is a sign of its ripeness. If you leave green olives on the tree long enough, they turn black and softer in texture. For fermenting, I prefer the crisp, green olives that are just beginning to ripen. You can tell because the olive is starting to turn slightly yellowish. Green olives are more bitter and very healthy due to their high polyphenol content.


  • fresh green olives
  • rock salt
  • water
  • large bowls
  • bail glass / glasses


Examine olives thoroughly and discard fruit with dark spots or black dots. Dark spots become mushy in the course of fermentation, and the black dot indicates an infestation of olive fly. If some olives are already blackened in the sun, it is not a problem, they are a delicious addition.

Water olives

Put olives in one or more large bowls and let them float in plenty of water for 10-14 days. Change the water daily. The fruits will lose their strong green color, become more and more yellowish and at the same time lose their bitterness.

Move the olives in the water 1-2 times per day and check for damaged areas. Olives affected by fly disease, which were previously imperceptible, may now appear. To check, take a knife and cut into the questionable olive. If you see small blackish cavities in the flesh of the olive, please throw it away. Although it hurts one' s heart, all damaged fruit must be removed immediately.

After 10 days you can taste the first olive. The goal is a pleasant bitterness, which is achieved after 10-14 days. The olives should not be allowed to soak longer before further processing. During lactic fermentation, the olives lose even more of their bitterness.

Put olives in brine

Cover the olives in the fermentation jars with water. Remove the water again, add 3% salt and let it dissolve. This is best done by stirring vigorously. Add the brine back into the jar with the olives. Note on the vessel how many grams of salt were used! This is especially important if you have several vessels of different sizes.

Leave the olives to ferment in the brine for two weeks. After 14 days, open the jars, take out some brine and dissolve it with the same amount of salt that was used in the first brine. That's why you noted the grams on the jars. Fill the now about 6% brine up again and close the jars.

HINT: If during the first fermentation kahm yeast formed, you can remove it immediately after opening the jars. This is best done with an absorbent cloth.

Hopefully the olives smell fantastic, even though they can still be quite bitter. Now the jars are placed in a dark and cool place and best just forgotten for a few months. Olives are slow food and another test of patience for fermentistas.

Ferment olives for at least 8 weeks

The lactofermentation gives the olives their unique flavor and the lactic acid bacteria bring a positive effect on the gastrointestinal microflora. The polyphenols contribute to cell health as antioxidants and have additional anti-inflammatory effects. Lactic acid fermentation is really fantastic!

If you like the taste of the olives after 8, 12 or more weeks, you can portion them into smaller screw-top jars and store them cold. Or eat them right away. Or give them as a gift. Fermented olives are really great.

If you enjoy green fermented olives, I recommend you also get inspired by my other mediterranean ferments.


    • Moin Horst,

      kiekste mal, dass wusste der gute Sandor nicht, und ich bis eben auch nicht. Danke für’s Aufschlauen! Das Rezept wird davon zum Glück ja nicht beeinträchtigt.

      Best regards,

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