Natural black olives – beyond the denomination (‘black olives’) – are not black in color but brown or reddish-brown, furthermore uneven, with various shades of color. Never truly black, except on the tree before harvesting. Only those colored through iron oxidation, added in the form of ferrous gluconate or ferrous lactate, are instead black as ink. How to recognize them? On the label, the ingredient list of the colored drupes must include the ferrous gluconate (E 579), preceded by the wording ‘stabilizer’.
The coloring of olives through iron oxidation started in California, adopting the coloring technique of dried plums. This processing, also experimented in Italy starting from the 1950s-60s of the last century, had industrial development in Spain in the 1970s. For presentation needs of the cultivar Spanish – in particular, the famous Hojiblanca – which if left to mature become soft and unworkable.
Spanish producers have been able to respond to market needs – and recover at least the semi-ripe olives as table olives (more profitable than those for oil) – refining the Californian coloring technique. Thus promoting the consumption of colored black olives.
The nutritional qualities e organoleptic of colored black olives are, moreover, negligible beyond the appearance. Natural black drupes like the Gaeta PDO olives, the Apulian Leccino or Taggiasca olives are distinguished instead by specific flavors and aromas. Which are independent from the intensity and uniformity of color. The same applies to various types of Greek black olives.
The Kalamata, for example, are natural black olives, moreover highly prized. In Greece, the pH of these olives is lowered by adding a small amount of vinegar to the brine, to prolong their preservation. Oil is added to give shine and to prevent oxidation of the olives, so that they maintain a reddish-brown color rather than tending to dull black.
Dario Dongo, lawyer and journalist, PhD in international food law, founder of WIISE (FARE - GIFT – Food Times) and Égalité.
