Olives have been used by humans for food since the early Bronze Age or for at least 5000 to 6000 years.

The olive is a species of small tree in the family Oleaceae (related to lilacs) and is naturally found in much of Africa, the Mediterranean Basin and southern Asia as far east as China. The olive tree’s fruit, also called the olive, is of major agricultural importance in the Mediterranean region as the source of olive oil.

The fruit is actually a small drupe (featuring an interior stone or pit) that may be as small as a ¼ inch to an inch to as large as an inch long. Olives are harvested in the green to purple stage. There are hundreds of cultivars of the olive which determine their color, size, shape, as well as the qualities of olive oil. Olives may be used primarily for oil, eating, or both. Olives cultivated for consumption are generally referred to as table olives.

Table olives

Table olives are classified into 3 groups according to the degree of ripeness before harvesting.

Green olives. Picked when they have obtained full size, but before the ripening cycle has begun. Usually shades of green to yellow.

Semi-ripe or turning-color olives. Picked at the beginning of the ripening cycle, when the color has begun to change from green to multi-color shades of red to brown. Only the skin is colored as the flesh of the fruit lacks pigmentation at this stage, unlike that of ripe olives.

Black olives or ripe olives. Picked at full maturity when fully ripe. Found in assorted shades of purple to brown to black.

Raw or fresh olives are very bitter.  To make them palatable, olives must be cured and fermented, thereby removing the bitter phenolic compound. Once ripening occurs the levels of phenolics sharply decline through their conversion to other organic products which renders some cultivars edible immediately.

The curing process may take from a few days, with lye, to a few months with brine or salt packing. With the exception of California style and salt cured olives, all methods of curing involve a major fermentation involving bacteria and yeast that is of equal importance to the final table olive product.

There are many types of preparations for table olives depending on local tastes and traditions. The most important commercial examples are:

Spanish or Sevillian type. Most commonly applied to green olive preparation. Olives are soaked in lye. Around 60% of all the worlds’ table olives are produced with this method. Once fermented, the olives are placed in fresh brine and acid corrected ready for market.

Sicilian or Greek type. Applied to green, semi-ripe and ripe olives. Almost identical the Spanish type fermentation process, however the lye treatment process is skipped and the olives are placed directly in fermentation vessels full of brine. The brine is changed on a regular basis to help remove the phenolic compounds.

Picholine or directly-brined type.  Can be applied to green, semi-ripe or ripe preparations. Olives are soaked in lye typically for longer periods than Spanish style (e.g. 10–72 hours) until the solution has penetrated three-quarters of the way into the fruit. They are then washed and immediately brined and acid corrected with citric acid to achieve microbial stability.

Water-cured type. Can be applied to green, semi-ripe or ripe preparations. Olives are soaked in water or weak brine and this solution is changed on a daily basis for 10–14 days.

Salt-cured type.  Applied only to ripe olives and usually produced in Morocco or Turkey and other eastern Mediterranean countries. Once picked, the olives are washed and packed in alternating layers with salt. The high concentrations of salt draw the moisture out of olives, dehydrating and shriveling them until they look like a raisin. Once cured, they are sold in their natural state without any additives.

California or “artificial ripening” type. (Olives without fermentation). Applied to green and semi-ripe olives. Olives are placed in lye and soaked. Upon removal they are washed in water injected with compressed air. This process is repeated several times until both oxygen and lye have soaked through to the pit. The repeated, saturated exposure to air oxidizes the skin and flesh of the fruit, turning it black in an artificial process that mimics natural ripening. Once fully oxidized or “blackened”, they are brined and acid corrected ready for eating.

Even though more attention has been sometimes been given to their delicious oil than their whole food delights, olives are one of the world’s most widely enjoyed foods. We think about olives not as fruit but as a vegetable that can be added to salads, meat and poultry dishes and, of course, pizza.

Kalamata olives are one olive variety that deserves special mention. Authentic Kalamata olives come from Kalamon olive trees in southern Greece and get their name from Kalamata, their city of origin. European Union (EU) law provides this type of olive with Protected Geographical Status and Protected Designation of Origin and does not allow product labeling as “Kalamata” unless the olives have come from this specific area.

However, outside of the European Union countries, there are no binding legal standards for labeling of Kalamata olives. In the U.S., many canned and jarred olives are referred to as “Kalamata-style” or “Kalamata-type” olives and these olives are not olives grown in the Kalamata area of southern Greece. Genuine Kalamata olives are usually allowed to ripen fully before harvest.

How to Select and Store

While olives have been traditionally sold in jars and cans, many stores are now offering them in bulk in large barrels or bins (often called an “olive bar”). Buying bulk olives will allow you to experiment with many different types with which you may be unfamiliar and to purchase only as many as you need at one time.

While whole olives are very common, you may also find ones that have been pitted, as well as olives that have been stuffed with either peppers, garlic or almonds. If you purchase olives in bulk, make sure that the store has a good turnover and keeps their olives immersed in brine for freshness and to retain moistness.

When selecting olives from an olive bar, you’ll often be faced with a wide variety of color options and textures. It’s not uncommon to find color varieties of olives that include green, yellow-green, green-gray, rose, red-brown, dark red, purplish-black and black. It’s also not uncommon to find several different textures, including shiny, wilted, or cracked. The size of olives may range from fairly small to fairly large or jumbo. Each of these options among olive varieties can provide you with valuable health benefits. In general, regardless of the variety you choose, select olives that still display a reasonable about of firmness and are not overly soft or mushy.

If you are purchasing olives in a can and don’t use them immediately after opening, they can usually be safely stored in sealed container in your refrigerator for one to two weeks. Whether brine-based, acid-based, or water-based, you can transfer the canning fluid along with the olives into your sealed refrigerator container. Glass jars of olives can be stored directly in the refrigerator for the same period of time, and in the case of some brine-cured olives, for up to one to two months.

Tips for Preparing Olives

To pit olives, press them with the flat side of a broad bladed knife. This will help break the flesh so that you can easily remove the pit with your fingers or the knife. The brine in which olives are packed can be used as a replacement for salted water in recipes.

A Few Quick Serving Ideas

  • Olive tapenade is a delicious and easy-to-make spread that you can use as a dip, sandwich spread, or topping for fish and poultry. To make it, put pitted olives in a food processor with olive oil, garlic, and your favorite seasonings.
  • Toss pasta with chopped olives, tomatoes, garlic, olive oil and fresh herbs of your choice.
  • Marinate olives in olive oil, lemon zest, coriander seeds and cumin seeds.
  • Add chopped olives to your favorite tuna or chicken salad recipe.
  • Set out a small plate of olives on the dinner table along with some vegetable crudités for your family to enjoy with the meal.