🫒 Spanish-style green olives

Seville-style olives are green table olives that are first treated with lye and then fermented in brine. This is the most common industrial method, and it is also called the Spanish style. The fruit is picked when it has finished growing but has not yet started to darken, when its colour ranges from green to straw yellow. The varieties used most often are Manzanilla de Sevilla, Gordal Sevillana and Hojiblanca.

First the olives are put into a weak solution of caustic soda, 2–3.5 per cent according to the International Olive Council. They stay in the lye until it has soaked through about two thirds of the flesh: it breaks bitter oleuropein down into substances that are not bitter. The lye is then washed out with water; modern rinsing takes 12–15 hours.

Next the olives go into brine with about five per cent salt. Here lactic acid bacteria do the work, above all Lactobacillus plantarum: they turn the sugars in the fruit into lactic acid, and the brine grows more acidic until the pH falls to about 4–4.5. It is the acid and the salt that preserve the olives.

The International Olive Council standard requires at least 5 per cent salt and a pH no higher than 4.0 for these olives. After fermentation the fruit is sorted and often pitted and stuffed with pepper or anchovies. If fermentation goes wrong, defects appear, such as gas pockets or an unpleasant smell.