Olives
The collection and the use of olives as food have its origins in Prehistoric Greece.
The Olive history is identical with that of Olive Oil. Thus, there is no question where the man used for the first time the olive as food; this took place in Crete about 3500 BC in the Early Minoan times. Since then, 5500 years passed and little things changed.
Strictly speaking, the only difference from the antiquity and the modern times is just the broadness of the expansion of the olive tree.
Today, commercial olive production generally occurs in two geographic belts around the world, between 30º and 45º (both North and South), where the climatic requirements for growth and fruitfulness can be found.
Most of the production of olives takes place in the Mediterranean Basin.
The Olive fruit is classed botanically as a drupe, similar to the peach or plum. Within the stone are one or two seeds.
Olives tend to have maximum oil content (about 20-30 percent of fresh weight) and greatest weight six to eight months after the blossoms appear. At that stage they are black and will continue to cling to the tree for several weeks. Fruits for oil extraction are allowed to mature, but, for processing as food, immature fruits are picked or shaken off the tree.
Olives are grown mainly for the production of olive oil. Fresh, unprocessed olives are inedible because of their extreme bitterness resulting from a glucoside that can be neutralized by treatments with a dilute alkali such as lye. Salt applications also dispel some of the bitterness. The processed fruit may be eaten either ripe or green.
On our days, the best olive type for food is considered the Greek "Kalamata Olive" (Calamon Olive), an almond-shaped Greek olive that ranges in length from about 1/2 to 1 inch.
Kalamatas olives (Calamon) are a dark eggplant color and have an excellent flavor that can be rich and fruity. They're often slit to allow the wine vinegar "Marinade" in which they're soaked to penetrate the flesh.
Kalamatas olives are marketed packed in either olive oil or vinegar. This type of olive is found exclusively in Greece.

Types of  Greek olives
The most important types of Greek olives are the Black Olives and the Green Olives.
Olives are selected based on three factors, which are the year of harvest, the type and the size. Olives should be eaten within 18 months after production date. Their size varies from very small to giant called as "mammoth". Olives are measured by their number per liter of net content. One liter of net content can hold from 80 to 400 olives depending on the size.

·         SIZE: The olive's suitability for table consumption is a function of its size, which is important to presentation. Olives between 3 and 5 g are considered medium-sized, while those weighing over 5 g are large.

·         SHAPE: Fruits that are more or less spherical in shape usually sell best, although some elongated ones also find flavor.

·         STONE: The stone should come away easily from the flesh and a flesh: stone ratio of 5 to 1 is acceptable; the higher this ratio the better the commercial value of the olives.

·         SKIN: The skin of the fruit should be fine, yet elastic and resistant to blows and to the action of alkalis and brine.

·         SUGAR CONTENT: A high sugar content in the flesh is an asset. The lowest acceptable level is 4%, especially in olives that undergo fermentation.

·         OIL CONTENT: Oil content should be as low as possible because in many cases it impairs the keeping properties and consistency of the processed fruit. Only in certain types of black olives is a medium to high oil content desirable.                                                                                    

Green Olives
Green olives are obtained from olives harvested during the ripening cycle when they have reached normal size, but prior to color change. They are usually hand picked when there is a slight change in hue from leaf-green to a slightly yellowish green and when the flesh begins to change consistency but before it turns soft. Color change should not have begun. Trials have been run to machine harvest table olives, but owing to the high percentage of bruised fruit they had to be immersed in a diluted alkaline solution while still in the orchard. Recently harvested, the olives are taken to the plant for processing on the same day if possible.

How are they processed?
The olives are treated in a diluted lye solution (sodium hydroxide) to eliminate and transform the oleuropein and sugars, to form organic acids that aid in subsequent fermentation, and to increase the permeability of the fruit. The lye concentrations vary from 2% to 3.5%, depending on the ripeness of the olives, the temperature, the variety and the quality of the water. The treatment is performed in containers of varying sizes in which the solution completely covers the fruit. The olives remain in this solution until the lye has penetrated two thirds of the way through the flesh. The lye is then replaced by water, which removes any remaining residue and the process is repeated. Lengthy washing properly eliminates soda particles but also washes away soluble sugars which are necessary for subsequent fermentation.
Fermentation is carried out in suitable containers in which the olives are covered with brine. Traditionally, this was done in wooden casks. More recently, larger containers have come into use that is inert on the inside. The brine causes the release of the fruit cell juices, forming a culture medium suitable for fermentation. Brine concentrations are 9-10% to begin with, but rapidly drop to 5% owing to the olive's higher content of interchangeable water.
At first Gram-negative bacteria multiply, but after a week and a half they disappear. They are a consequence of contamination produced in the plant installations, and in the atmosphere and brine and can be avoided by stepping up hygiene measures. At a pH level of 6 and upwards, lactobacilli develop massively until the Gram-negatives disappear and the brine attains a pH of 4.5. There is a predominance of Lactobacillus plantarum which produces lactic acid from glucose almost by itself. When the fermentable matter is spent, acid formation ceases. Yeasts appear together with the lactobacilli. Fermentative yeasts do not cause deterioration but oxidant yeasts consume lactic acid and raise the pH level and may therefore jeopardize the process.
Under certain conditions normal fermentation processes can be altered by the presence of undesirable microorganisms which can transmit poor organoleptic properties to the olives or impair their keeping properties. Gas pocket fermentation is caused by the Gram-negative bacilli in the first stage of fermentation, but can be controlled by intensifying hygiene precautions when the olives are delivered to the plant, as well as during lye treatment and washing. If gas pockets still appear in spite of these measures, the pH level can be lowered to 4 by adding an acid. Butyric fermentation is well controlled by ensuring the proper pH level. Putrid fermentation is caused by poorly-kept containers and bad water. Lastly, there is a type of deterioration known by its Spanish name of "zapaterνa" (cobbler's) which produces an unpleasant taste and odour at the end of the fermentation process, often coinciding with rising temperatures in the spring or early summer. It is produced by bacteria belonging to the Clostridium and Propioni-bacterium genus. The right combination of brine concentration and pH level (5% salt and 4.5 pH) helps to control fermentation processes.
When properly fermented, olives keep for a long time. If they are in casks, the brine level must be topped up. At the time of shipment, the olives have to be classified for the first or second time as the case may be. The original brine is replaced and the olives are packed in barrels and tin or glass containers. Sometimes they are stoned (pitted) or stuffed with anchovies, pimento, etc.
The bitterness of the olives is removed by treating them in a 3-3.5Ί B lye solution in which they are left for 8 to 72 hours until the lye has penetrated three-quarters of the way through the flesh. They are rinsed several times over the next day or two, and then placed in a 5/6% brine solution for two days. A second 7% brine solution is prepared, and acidity is corrected with citric acid (pH 4.5). After 8-10 days they are ready to be eaten and retain their intense green colour. Sometimes the consignment has to be postponed, and it is necessary to store the olives. This is easy, as long as temperatures do not rise. The olives can stay in an 8% brine solution until spring, but then it has to be raised to 10%. In larger installations they can be kept in cold storage, at a temperature of between 5Ί and 7Ί C, in a 3% brine solution.Before shipment, the olives are washed repeatedly, sorted and packed in suitable containers in 5Ί or 6ΊB brine.

 Black olives in brine
In Greece they use the Conservolea variety, with some 200 olives per kilo. The fruits are handpicked when they are black, but before they are overripe and shriveled from frost. They have to be transported as quickly as possible to the processing plant where they are sorted, washed and immersed in a brine solution at a concentration of 8-10%.
Large-scale plants use big 10-20 tones vats, whilst small scale processors still use wooden vats. At the start of fermentation, the olives must be kept from contact with air, so the vats are covered and made airtight. The brine stimulates the microbial fermentation activity and reduces the bitterness of the oleuropein. The brine concentration drops to 6%, so it is necessary to increment it to 8% or even 10%. This is done by mixing the solution with the olives by means of a pump, which improves circulation. When the bitterness has been sufficiently weakened -this varies widely- the fruit can be sold. The colour fades during the process and can be corrected by aerating the olives for two or three days, although sometimes they are treated with 0.1% ferrous gluconate to make them darker. Finally, the olives are selected and packed in internally-varnished barrels or cans which are filled with fresh brine at 8%. They are popular on the market due to their slightly bitter taste and aroma.
These are also packed in vinegar (25% of the volume of the brine) and even undergo heat treatment; a few grams of oil are then added to each can to form a surface layer. This type of preparation is used for the Greek Kalamata variety. These are elongated, medium-sized olives which are slit laterally before being put into cans.

Black olives in dry salt
Also of Greek origin, these are prepared using overripe olives of the Megaritiki variety. They are vigorously washed and placed in baskets with alternating layers of dry salt equivalent to 15% of the weight of the olives. The result is an olive that is salty, not very bitter, that looks like a raisin and is for local consumption.
Finally, a mention should also be given to the numerous styles of table olive preparations in the different olive-growing regions. Some examples are olives treated solely with water to sweeten them prior to crushing or splitting, which facilitates washing. In many cases, before being eaten the olives are seasoned with herbs, pieces of orange, lemon, garlic, paprika, oregano, etc. Until the turn of this century, the table olive market was local, but since then it has expanded to non-producing areas where table olives have become popular. This is particularly true of the Spanish, Greek and Californian types.