Optimal harvesting period for cvs. Madural and Verdeal Transmontana, based on antioxidant potential and phenolic composition of olives

- Madural and Verdeal Transmontana olives have different maturation patterns.
- Maturation process influenced phenolic composition and antioxidant activity.
- Antioxidant potential increases from green to black olives.
- Oleuropein and hydroxytyrosol are heavily affected by olives maturation.
- Harvesting period should begin sooner than usual, in the first weeks of November.

In the present study we propose to determine an approximate optimum harvesting period for table olives and olive oil of two Portuguese olive cultivars (Madural and Verdeal Transmontana) based on phenolic modifications (HPLC/DAD) and antioxidant activity (scavenging capacity on 2,2-diphenyl-1-picrylhydrazyl and reducing power). Samples were collected from almost edibility to slightly over-mature. The sum of polyphenols, as well as its most abundant components oleuropein and hydroxytyrosol, decreased during this maturation period, more intensively in Madural than Verdeal Transmontana. In their green stages an antioxidant potential loss was gradually observed in both olive cultivars, while in the latter purple-black phases a slight increase in the antioxidant activity was observed. Both phenolic profile and antioxidant activity were highly correlated with the maturation process. A principal component analysis showed the particular effect of maturation in both olive cultivars.Based on the acquired knowledge we can advance that, for these cultivars and geographical region, olives harvest for table olives, traditionally collected sooner, can be performed in the middle of September. For olive oil harvesting can occur in the first days of November, giving priority to cv. Madural rather than Verdeal Transmontana, in order to enhance the bioactivity, phenolic composition and stability of olive oils.