Olives, Brine-Cured Greek Style

The long one. No cutting, no lye — just salt, time, and lactic bacteria doing the work a chemical would do in a day. At least three months, often six or more, and the diagnostic detail is that the brine goes cloudy: that cloud is the ferment, and it is the tell that separates an olive that grew its own acid from one that had acid poured over it.

Ingredients

THE OLIVES

• 10 lb mature olives, fully coloured dark red to purplish black, firm, picked before the first frost

STARTING BRINE

• 1 gallon cool water
• 3/4 cup pickling salt (8 oz)

STRONGER BRINE, FROM DAY SEVEN

• 1 gallon cool water
• 1 1/2 cups pickling salt (1 lb)

STORAGE BRINE, IF THEY ARE KEEPING

• 1 gallon cool water
• 1 1/4 cups pickling salt (13 oz) — this is the 10% figure

Directions

Key ingredients

Salt · Olive Oil

1. Step 1 - Use mature, fully coloured fruit, and sort by size. Dark red to purplish black, firm, before the first frost. Manzanillo, Mission and Kalamata are the usual varieties. Green-ripe olives take considerably longer in brine than black ones.
2. Step 2 - Choose a container that seals, and not a small one. Airtight, 1 quart minimum — glass, food-grade plastic or a crock. A container that cannot be closed lets the surface breathe, and the surface is where the mould grows.
3. Step 3 - Start at 3/4 cup (8 oz) salt per gallon, with the lid LOOSE. Cover the olives completely. The lid stays loose because this is a fermentation — it makes gas, and a sealed jar of fermenting olives will bulge or pop. Hold at 60-80 °F, out of the sun.
4. Step 4 - After seven days, swap the brine. Pour it off and replace with the stronger one: 1 1/2 cups (1 lb) salt per gallon. Now the lids go firm. If a lid bulges, loosen it — the ferment is still running.
5. Step 5 - Wait. At least two months, and expect longer. Brine curing takes at least 3 months and may take 6 or more, depending on variety, maturity, temperature, salt and the acidity of the brine. If you want them less bitter sooner, replace the brine monthly for two or three months — each change carries away more oleuropein.
6. Step 6 - Watch the brine, not the calendar. Cloudy is correct: that is the lactic ferment. Skim any scum from the surface and keep every olive submerged. Slimy, foul-smelling, or fruit going mushy is a different story — see the note on softening below.
7. Step 7 - For long storage, move to a 10% brine. 13 oz (1 1/4 cups) of pickling salt per gallon of water. Properly fermented and airtight, they keep a year. Some colour fades during curing and comes back on contact with air, and the fruit shrivels slightly in strong brine — both are normal.
8. 🔴 These are not a canned food. Brine-cured olives are not on 8267’s pressure-canning list. Refrigerated or in strong brine is where they live.

Notes

Where the numbers come from. Olives: Safe Methods for Home Pickling, UC ANR Publication 8267 (Yada and Harris, UC Davis, 2007), read in full. An earlier version of this recipe was built from a county extension digest of that publication and has been corrected against the original.

⭐ What is actually happening, and why it takes so long. Nothing is being added. Lactic acid bacteria ferment the sugars in the fruit into lactic and acetic acid, and — this is the part worth knowing — the fermentation also breaks the chemical bond between oleuropein and the sugars in the olive, which is what lets the bitterness leach into the brine. It is the slow biological version of what lye does chemically in twelve hours. You are not curing these olives; you are keeping the conditions right while something else does.

⭐ The cloudy brine is the section’s one universal tell. Across every pickled food I have looked at, a cloudy brine means the acid grew in the jar and a clear one means it was poured in. An olive is the clearest case of it.

🔴 Softening is the failure mode, and it is fast. Pectin-degrading enzymes from surface moulds and bacteria can soften a batch within two weeks. UC’s answer is the 10% storage brine — 13 ounces (1 1/4 cups) of pickling salt per gallon — which is the same figure Italy’s ISS publishes for home-preserved olives, arrived at from a completely different direction. Keep the fruit submerged and skim the surface. ⚠ Ascolano and Barouni soften regardless.

Cultivars. Manzanillo, Mission and Kalamata for this method. Kalamata as sold commercially is slit and fermented 8-12 months in 6-10% brine. Firm skin and moderate oil are what you want; a high-oil pressing cultivar turns to paste.

Related: Olives, Sicilian Style in Brine is the green-olive ferment — same idea, seasoned brine, different fruit. Olives, Water-Cured (Green) is the week-long version, and Olives, Lye-Cured (Reference) the twelve-hour one.