Olives

Olives are a naturally bitter fruit fermented or cured with lye or brine to make them more palatable.
Green olives and black olives are typically washed thoroughly in water to remove oleuropein, a bitter glycoside.
Green olives are allowed to ferment before being packed in a brine solution. American black ("California") olives are not fermented, which is why they taste milder than green olives.
In addition to oleuropein, freshly picked olives are not palatable because of phenolic compounds. (One exception is the throubes olive, which can be eaten fresh.) Traditional cures use the natural microflora on the fruit to aid in fermentation, which leads to three important outcomes: the leaching out and breakdown of oleuropein and phenolic compounds; the creation of lactic acid, which is a natural preservative; and a complex of flavoursome fermentation products. The result is a product which will store with or without refrigeration.
Curing can employ lye, salt, brine, or fresh water. Salt cured olives (also known as dry cured) are packed in plain salt for at least a month, which produces a salty and wrinkled olive. Brine cured olives are kept in a salt water solution for a few days or more. Fresh water cured olives are soaked in a succession of baths, changed daily.[50] Green olives are usually firmer than black olives.
Olives can also be flavoured by soaking in a marinade or pitted and stuffed. Popular flavourings include herbs, spices, olive oil, chili, lemon zest, lemon juice, vinegar, and juniper berries; popular stuffings include feta cheese, blue cheese, pimento, garlic, cloves,jalapenos, almonds, and anchovies. Sometimes, the olives are lightly cracked with a hammer or a stone to trigger fermentation. This method of curing adds a slightly bitter taste.