The potential of calcium nanoparticles in posthaverst conservation of fresh-cut seedless watermelon (Citrullus lanatus)

In fresh cut (FC) watermelon, texture loss on the flesh leads to tissue softening and greater water soaking, reducing the shelf life. This study was assessed the effect of calcium nanoparticles (NP) [CaO-NP and Ca(OH)2NP] at three concentrations (100, 150, and 200 mg L- 1) compared to control (water) and CaCl2 (1 %, w/v), on FC seedless watermelon. Treatments were applied by 3-min immersion and stored for 12 d at 5 +/- 1 degrees C. Quality, oxidative stress and softening variables were determined every four days. The postharvest quality variables for all treatments were subjected to principal component analysis (PCA), followed by cluster analysis, using the first three dimensions obtained from PCA (explaining 71.68 %). The PCA results showed that visual quality (VQ) was the most influential variable. The treatments with Ca(OH)2-NP positively affected FC watermelon while the treatments with CaO-NP showed a negative correlation. Furthermore, the PCA analysis showed a negative correlation between visual quality and the variables juice leakage (JL) and weight loss (WL). Cluster analysis showed that Ca(OH)2-NP treatments at 8 and 12 d were globally closer to the control at 0 d followed by all treatments applied at 4 d of storage. In general, positive effects were observed in the FC seedless watermelon treated with 100 and 150 mg L- 1 Ca(OH)2-NP, compared to the FC seedless watermelon treated with CaO-NP in the same concentrations, in the parameters of water soaking, lipid peroxidation and in the PME activity after 12 d of storage. FC seedless watermelon treated with 100, 150 and 200 mg L- 1 Ca(OH)2-NP showed 2.2, 4.4 and 3.2 times less water soaking, respectively, compared to the values observed in the same concentrations of CaO-NP. A similar trend was observed in the values of lipid peroxidation parameters and PME activity, where 2.5, 3.2 and 2.7 times less lipid peroxidation and 1.2, 1.4 and 1.8 times lower PME activity were observed. No differences were detected in CAT and POD activities between CaO-NP and Ca(OH)2-NP treatments. In general, the best quality results were obtained in the FC seedless watermelon fruit treated with the different concentrations of Ca (OH)2-NP.