Irrigation effects on fruit yield, phenolic composition and fermentation of naturally green olive processing from cv. ascolana tenera

The water availability in the traditionally olive growing area is getting smaller and smaller so the optimization of irrigation to avoid losses or reduce water volumes is of crucial importance. In the present work the influence of different irrigation strategies on crop performance and quality of ‘Ascolana tenera’ olive cultivar, was investigated. A rainfed control (T0), and two treatments receiving a water depth equivalent to 33 and 66% (T33p and T66p, respectively) of estimated crop evapotranspiration (ETc) from the pit hardening stage, and a treatment with a 66% of ETc (T66w) during the entire season (25/5-4/10), were tested. Furthermore naturally green olive processings were carried out. Results showed a linear fresh yield enhancement as crop water availability increased mainly due to the increase of fruit size, whereas less evident differences were detected for fruit number per tree and pulp/stone ratio. Total phenolics and analysis by GC-MS in olive fruit as affected by irrigation treatments were carried out and phenolic profiles compared. Oleuropein and its hydrolytic derivatives as well as other simple and characteristic olive fruit phenolic compounds (tyrosol, 3,4-dihydroxyphenylglycol and vanillic acid), were mainly detected. Concentration of total phenolics was lower in the olives from irrigated treatments. Differences in concentration of phenolics were also observed between fresh and processed olives. During fermentation, sugar consumption, titratable acidity and pH evolution were also monitored.