Phenolic compounds, maturation and quality in fresh green olives for table use during exposure at 20 °C after preharvest ReTain treatment

The aim of this work was to investigate the effects of ReTain (4.15%, w/w, amino ethoxyvinyl glycine, AVG), an ethylene synthesis inhibitor, sprayed at concentrations up to 250 mg L−1 before the green maturation of ‘Konservolia’ olives (Olea europea L.) on colouring in fruit harvested up to 20 d later and on ripening variables in fruit selected green at harvest and exposed at 20 °C for up to 7 d. Earlier applications and higher ReTain concentrations were more effective in preventing colouring at harvest, and softening and green losses at 20 °C. Ethylene production was non-measurable or very low. Increased respiration was observed only in early treated fruit with ReTain on day 1 at 20 °C, but respiration reduced in all fruit during exposure time. Oleuropein (OE), the major phenolic, hydroxytyrosol, tyrosol, luteolin 7-O-glucoside, luteolin 4-O-glucoside, rutin, and ferulic and p-coumaric acids were measured in all samples. OE, confirmed by HPLC–ESI-MS, and total antioxidant activity were lower in ReTain treated fruit than in controls and remained so after the increases at 20 °C in all fruit. Conclusively, ReTain could be used to extend the harvest period and/or improve the quality of fresh green olives for table use, and particularly those destined for Spanish-style processing.

► Preharvest ReTain treatments were applied before olive green maturation. ► ReTain reduced green loss before and after harvest. ► Increased firmness and decreased OE were observed in ReTain treated olives. ► OE and antioxidant activity increased in all fruit after harvest at 20 °C. ► ReTain can extend the harvest period and improve green olive quality for table use.