🧂 Brine

Brine is a solution of table salt in drinking water in which olives ferment and are stored. The salt holds back spoilage microbes while leaving room for lactic acid bacteria and yeasts. Depending on the method, brine contains roughly 5 to 10% salt; feta also matures in brine.

Brine strength depends on the method. Natural Greek-style black olives go into brine with 8–10% salt, and fermentation there is driven mostly by yeasts. Spanish-style green olives are covered after the lye treatment with brine of about 9–10% (other sources say 6–8%), but some of the salt passes into the fruit and the concentration drops to about 5%. Californian olives are held in 5–10% brine for 2 to 6 months before processing.

The International Olive Council standard sets a minimum salt level for the brine in which olives are sold if they are not pasteurised: 5% for lye-treated olives and 6% for natural ones; with preservatives or under refrigeration 4% is enough for lye-treated olives, while dried olives need 10%. Brine from fermented olives can hold up to a billion lactic acid bacteria and yeasts per millilitre. Finished Spanish-style olives are packed in brine with at least 8% salt, and to get fermentation off to a reliable start a little old brine is added to the fresh one.

Spent brines are the main environmental problem of table olive plants: they make up a fifth of the wastewater but about 85% of all the pollution. Efforts are made to reuse and treat them, combining bioreactors with ultrafiltration and nanofiltration. Feta also ripens in brine: after dry salting it is kept in brine with 7% salt, and in total the cheese matures for at least two months.

Why it matters to you. Because of the brine, olives are very salty: 100 g of canned green olives contains 1,560 mg of sodium, and Californian-style black olives 735 mg (USDA). The World Health Organization advises adults to have less than 2,000 mg of sodium a day, so if you watch your salt, mind the portion.