EFFECTS OF RETAIN PREHARVEST APPLICATION ON RIPENING PARAMETERS, PHENOLICS AND TOTAL ANTIOXIDANT CAPACITY OF GREEN TABLE OLIVES EXPOSED AT 20°C FOR UP TO 7 DAYS

Abstract

The effects of preharvest application with Re Tain concentrations up to 200 mg L -1 on color development, firmness, total phenolic concentration, total antioxidant capacity (TAC) and concentrations of oleuropein, hydroxytyrosol and tyrosol were investigated in 'Konservolia' olives harvested 15 days after the application was carried out before the green maturity state. All treated fruit were measured for color development, while only green fruit were further exposed at 20°C and 90% RH and used for the rest of the measurements after 1 and 7 d exposure. ReTain prevented the red coloration, and at 200 mg L -1 resulted in a higher frequency of dark-green olives and lower of red than controls, as observed at harvest. Ethylene production rates were low in all samples during exposure. ReTain at 200 mg L -1 was the most effective on firmness loss prevention during the whole assessment time. Total phenolic concentration, TAC and oleuropein concentration were lower in ReTain treated fruit than in controls on day 1, and although they increased in all samples during exposure, on day 7 the levels of oleuropein and TAC in fruit treated with 200 mg L -1 ReTain were still lower than those in controls. However, decreased oleuropein levels are desirable in green olives before the processing stage. Olives treated with 200 mg L -1 ReTain showed the highest concentrations of hydroxytyrosol and tyrosol on day 1, but after the non consistent changes in both phenolic compounds during exposure, the concentrations of each compound were at similar levels in all treated fruit on day 7. Results showed that 200 mg L -1 ReTain delayed the green maturation and could be used to extend the harvest season for green table olives.