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There are around 300 different types of olives on the market, ranging in color from green to black. The color says something about the degree of ripeness of the Mediterranean stone fruit. Each olive is colored green at the beginning of its development. When fully ripe, the color tones vary from violet-black to reddish-brown, depending on the variety. While the degree of ripeness of tree fruits is clearly recognizable, stone fruits from the trade are often difficult to assign to a ripeness stage.

fruit development

It takes about two to three months for the green stone fruits to ripen. During this process, the consistency of the pulp changes from firm to crunchy to soft. The aroma becomes increasingly milder as bitterness and pungency recede into the background. Unripe olives have a high content of polyphenols, which have a positive effect on health. For the production of olive oil, the stone fruits are harvested unripe, because the polyphenol content decreases significantly in the course of their development.

Ideal harvest time

Temperatures, number of hours of sunshine and water availability have a decisive influence on fruit ripening. The drupes are harvested after a lot of warmth and sun in autumn. In Germany, the olive tree only develops flowers and stone fruits in the wine-growing regions. Under the growth conditions prevailing here, Olea europaea bears the first olives over the course of the summer, which can be harvested for the first time from mid-November. At this time they are in the first stage of maturity. The olive tree fruits go through their ripening process until the end of December. If the weather is unfavorable, fruit ripening can extend into January. The stages of ripeness can be easily recognized by the color of the fruit:

  • early stage: green drupes are firm, low in oil and very bitter
  • middle stage: green-yellow to red-violet fruits have a slightly sweet taste and contain more oil
  • last stage: black fruits with a soft consistency and a mildly spicy taste.

Mature olive

When the stone fruits are ripe, they have neither a bitter nor a pungent taste. Its aroma is mildly spicy with a slightly sweet note, because the bitter substances have broken down as the fruit ripens. Their coloring differs depending on the variety. A deep black base tone that can have violet, reddish or brown nuances is typical. The flesh and stone also turn black.

Fully mature specimens are easy to pick from the tree. They can fall off the branch at any moment and take on unpleasant aromas on the ground, which is why a quick harvest is necessary. These properties are characteristic of ripe olives:

  • low content of polyphenols
  • higher in calories than immature specimens
  • contain more saturated fat

Tip: You can recognize oil from fully ripe olives by its golden yellow colour, because the harvested stone fruits no longer contain any chlorophyll.

Identify unripe fruit

In the trade, olives are often offered that only appear ripe at first glance. Their black coloration is an illusion because it did not come about through a natural maturing process. These specimens are often harvested in the early stages of maturity when they are still green in colour. They are then colored with the dye iron(II) gluconate. This increases their shelf life and changes the taste. Pay attention to the information in the list of ingredients. Black colored olives must be labelled, which you can recognize by the ingredient E 579. Another sign of colored and unripe fruit is the coloring of the flesh and stone. If these are still green, this indicates that the olives were harvested too early.

Tip: Green olives are inedible and must first be bathed in caustic soda. Then put the stone fruits in brine or vinegar and refine them with herbs.

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