Tree ripening and postharvest firmness loss of eleven commercial nectarine cultivars under Mediterranean conditions

- Flesh firmness and IAD were significantly affected by cultivar and ripening season.
- Early ripening cultivars lost flesh firmness faster than mid and late ripening cultivars.
- Softening behavior was highly dependent on cultivar and ripening season.
- Low acid nectarine cultivars showed a commercially more suitable softening behavior than acid ones.

On-tree and postharvest softening of 11 yellow flesh nectarine cultivars with different commercial harvest seasons (early, mid and late) were studied under Mediterranean conditions (Lleida, NE-Spain). Fruit were harvested weekly at five consecutive harvest dates (from H1 to H5) over three consecutive years (2009-2011). Diameter, percentage of skin overcolor (SC), flesh firmness (FF), IAD index (the difference in absorbance between 670 and 720 nm), visible reflectance spectra, soluble solids content (SSC), titratable acidity (TA), ethylene synthesis, objective skin color and postharvest softening rate were measured. The decline in flesh firmness and the IAD were both significantly affected by cultivar and ripening season. Low acid (TA < 6 g of malic acid L−1) cultivars such as 'Big Top', 'Nectareine', 'Honey Royale', 'Big Nectared' and 'Nectalady', had a lower firmness decline than acid ones (TA ≥ 6 g of malic acid L−1), both on-tree and during postharvest, resulting in a better commercial and postharvest performance. A high and significant positive correlation was found between IAD and flesh firmness (r = 0.72, P ≤ 0.01). Early cultivars tended to lose flesh firmness and IAD faster than mid and late cultivars. The softening rate during the postharvest period was mainly dependent on ripening season. Early ripening nectarines soften faster than mid and late ones.