The Fate of Chlorophylls in Alkali-Treated Green Table Olives: A Review

This paper reviews the current knowledge regarding modifications to chlorophylls during the processing of green table olives treated with alkali. Particular attention is given to the pheophytinization reactions (substitution of Mg²⁺ by 2H⁺ in the chlorophyll chromophore group) that can take place because of pH and/or temperature changes and the possible sequential substitution of the 2H⁺ with Cu²⁺ within the chlorophyll porphyrin ring. These reactions may have a direct impact on the commercial value of olive productions as some naturally forming Cu-chlorophylls complexes (i) are identical to strictly forbidden colorants for table olives (E141) and (ii) have been identified as responsible for the unwelcome appearance of the so-called green staining alteration (characterized by bluish-green zones distributed over the olive skin of the drupes).