Shelf-Life of Bunched Carrots as Affected by Nitrogen Fertilization and Leaf Presence

Abstract

Nitrogen (N) fertilization is essential for adequate earliness and the commercial attractiveness of carrots, but its excess could generate fast decay during postharvest, mostly in bunched carrots exhibiting their highly perishable leaves. A field experiment was conducted over the 2016–2017 growing season to address the effects of two N fertilization rates (120 and 240 kg N ha−1, hereafter N120 and N240, respectively) and leaf presence/absence (leaf+ and leaf−) on physicochemical and compositional traits of carrots cv. ‘Dordogne’, after storage at 4.0 ± 0.5 °C, 95–96% relative humidity (RH) for 0, 3, 6, 12, and 24 days (hereafter S0–S24). Before storage, carrots were arranged in bunches and packaged in common low-density polyethylene (LDPE) pouches (thickness 95 μm), 54 × 24 cm size, with 16 holes of 5 mm size. N240 carrots compared to N120 showed higher cumulative weight loss (CWL) and firmness reduction, with differences at S24 equal to 108 vs. 41 g kg−1 fresh weight (FW) and 13.3 vs. 14.5 N, respectively. N240 compared to N120 increased also the color deviation (ΔE*ab, +126%) and nitrates content (+93%) of carrots and slowed down their temporal increase of total polyphenols and antioxidant activity. Leaf+ carrots compared to leaf boosted CWL and firmness reduction, with differences at S24 equal to 90 vs. 58 g kg−1 FW and 12 vs. 17 N, respectively. In addition, leaf presence increased reducing sugars (+17%) and decreased nitrates (−24%) contents. This research has shown the possibility of improving the desirable quality and shelf-life of carrots by halving the N dose commonly supplied by growers and marketing bunched carrots within 12 days from the start of storage.