The Erkence olive: the cultivar that sweetens on the tree

An olive picked from the tree cannot be eaten. A compound called oleuropein gives the fruit an unbearable bitterness, and removing it takes brining, cracking, scoring or a lye treatment. Everywhere in Turkey, the olive reaches the table only after one of these.

Erkence is the exception. Under the right conditions this variety loses its bitterness while still on the tree and becomes edible as it is. The process is called "hurmalaşma"; the product is known as hurma zeytin — the date olive.

Erkence in numbers

How the tree-ripening works

Long treated as a "climate miracle", the mechanism has been established by research — and it turns out to be microbiological.

Natural microorganisms carried on the wind — particularly Pseudomonas species — settle on the skin of the fruit. As the fruit ripens on the tree these microorganisms start a spontaneous fermentation, and the oleuropein responsible for the bitterness breaks down. In other words, the step carried out in a processing plant for table olives happens here in the open air, on the branch.

That has two practical consequences:

• No salt. Because it never goes into brine, hurma zeytin contains zero salt. For someone on salt restriction — where nearly every table olive option is ruled out — this is the one that remains.
• Tied to the locality. The same Erkence sapling planted elsewhere may not produce the effect; it depends on the variety and the local microbiota working together. This is why the product is known as Karaburun hurma olive — by its place, not its variety.

The genome of the date olive has also been mapped, so the genetic side of the phenomenon is now on record too.

The earliest harvest

Being the Aegean's earliest-ripening variety brings its own advantages: the fruit reaches the mill before the rest, it carries a price advantage as the season's first produce, and it is less exposed to the late period when the olive fly peaks.

Its place in the country

At 3.5% Erkence is Turkey's fourth most widespread variety — after Memecik (45%), Ayvalık (19%) and Gemlik (11%).

It also appears among the most important table-olive varieties: Gemlik, Ayvalık, Domat, Memecik, Erkence, Uslu, Eşek Zeytini, Yamalak Sarısı and Edincik Su.

Erkence is additionally counted among the pollinator varieties used for Ayvalık — so in grove planning it serves a purpose beyond its own crop.

Turkey's full variety distribution: olive varieties.

Why it is so little known

Erkence ranks fourth in tree stock and yet the consumer has never heard the name. The reason is how narrow the conditions for the date olive are: the tree-ripening doesn't happen every year, in every grove, on every fruit. Without the right humidity, temperature and microorganisms coming together, the fruit stays bitter like any other olive and goes to brine.

So the date olive is not manufactured but gathered. That is what makes it scarce and expensive.