Evolution of physicochemical constitution and cultivar-differential maturity configuration in olive (Olea europaea L.) fruit

Abstract

Analytical characterization of the ripening process is prerequisite to establishing cultivar-specific harvest maturity windows and safeguarding the quality of olive products. In this context, we profiled the ripening of select Cypriot olive (Olea europaea L.) cultivars ‘Ladoelia’, ‘Kato Drys’ and ‘Korakou’ juxtaposed against introduced ‘Koroneiki’. Fruit skin and flesh color-based maturity index (MI) evolved linearly over time but differentially among local cultivars. Anthocyanin content exhibited better correspondence to MI with progressive maturity. Cultivars varied widely in their sugar content (60.2–180.9 mg g−1 dw) and their fructose/glucose ratio, which impacted their relative sweetness. Putative connection of declining mannitol levels with oleogenesis during ripening was not supported by ‘Korakou’, wherein mannitol declined without concomitant oil accumulation. However, fruit firmness correlated negatively with oil content prompting harvest of table olives before oil peak. Succinic and oxalic acid levels may constitute valuable cultivar signature traits. Decline pattern in total phenolic content (TPC) during ripening was cultivar-specific, with oleuropein, rutin and hydroxytyrosol constituting the major constituents in diminishing abundance. No cultivar differences were observed in rutin content, while hydroxytyrosol and tyrosol levels were independent of maturity. At MI3, ‘Ladoelia’ had higher total phenolic content (TPC) than ‘Korakou’ and ‘Kato Drys’ but inferior to ‘Koroneiki’ (12.3, 9.9, 2.5 and 20.4 g kg-1 dw, respectively). Oleuropein relative content in ‘Ladoelia’ (85.6 %TPC) was higher than ‘Kato Drys’ (63.6 %TPC) and ‘Korakou’ (59.2 %TPC). ‘Ladoelia’ exhibited superior but maturity-dependent phenolic acids content. Our results corroborate a cultivar-specific application of MI supported by additional physicochemical parameters of maturity. The current findings may facilitate cultivar and product-specific integrative harvest maturity indices, which are especially critical for dual purpose large-fruited cultivars.