EFFECTS OF MINERAL AND ORGANIC FERTILIZATION AND RIPENING STAGE ON THE EMISSION OF VOLATILE ORGANIC COMPOUNDS AND ANTIOXIDANT ACTIVITY OF 'STARK REDGOLD' NECTARINE

Our objective was to investigate the effect of fertilization (mineral vs. organic) and ripening stage (pre-climacteric vs. climacteric) on the emission of volatile organic compounds (VOCs) and antioxidant activity of nectarine [Prunus persica, Batsch var. nectarina (Ait) Maxim.]. The trial was carried out in 2007 in an experimental orchard of cv. Stark RedGold grafted to GF677 peach x almond hybrid planted in 2001. The trees were subjected to mineral (N, 120 kg ha^-1 year^-1) or organic (compost, 10 t DW ha^-1 year^-1) fertilization from plantation, with treatments applied 40 days after full bloom at 60% of the annual rate and in September at 40%. A fruit sample was collected every day from 22 July to 3 August. The difference in the absorbance index (I_AD) of each fruit at each sampling date was measured by visible/near infrared spectroscopy (VIS/NIRs). Fruits were sorted into two groups corresponding to two ripening stages: pre-climacteric (I_AD >0.9 and flesh firmness > 50N) and climacteric (I_AD <0.4 and flesh firmness <15N). The day after each sampling, two nectarines per treatment (8 per day) were sealed in a jar for 50 minutes and VOC emission was measured in overhead air samples by gaschromatographic analysis. VOCs increased from pre-climacteric to climacteric ripening stage and were higher in fruit fertilized with compost than in those treated with mineral fertilizers. Linalool, dodecane, methyl-4-decenoate, 1-decene were among the molecules increased by compost dressing. While antioxidant activity was unaffected by ripening stage and fertilization, it was higher in fruit peel than in flesh.