The earliest cultivation of olive trees was probably over five thousand years ago, since Ancient Greek times.
Known for their oval shape, dark purple color, and intense flavor, Kalamata olives are hand-picked to avoid bruising. Their optimal harvest time is late fall, while other varieties are usually picked earlier, which explains why they are still green. It is all about balance. If the olives are too green, the fruits, along with the olive oil produced, will taste bitter. If they are too black, the quality will be lost.
Kalamata olives contain a stone in the middle, and generally, they are not pitted before being sold. However, when fresh the olives are incredibly bitter, and so they enter a process of ‘debittering.’
There are two different ways of doing this.
First, the short way involves soaking the olives in brine for a week. After this, workers pack them with brine, wine vinegar, slices of lemon and olive oil.
The long way involves making a slit in each olive, and storing them in 10% salt-water for fermentation until they de-bitter. This process usually takes around three months.
Source: Greek City Times