Effects of copper nanoparticle (CUNP), putrescine and their combined applications on postharvest storage of Göğ (Gök) grape variety

The short shelf life and quality losses of grapes after harvest constitute an important problem in agricultural production. This study aimed to investigate the effects of copper nanoparticles (CuNP), putrescine (PUT) and their combined applications on the postharvest storage of Gok grapes. In the study, the changes in the quality, biochemical and enzymatic properties of grapes were examined with 30 ppm CuNP, 0.5 mM putrescine and their combination. The study results showed that the effects of the applications on weight loss were insignificant, while their effects on the amount of water-soluble solids and titratable acidity were significant. In particular, PUT and combined applications preserved these properties better. It was seen that the CuNP application alone was not better than the control. When the color values were examined, it was seen that the applications only significantly affected the Hue angle value. All of the total contents - phenolic, flavonoid, carbohydrate and protein - from the biochemical contents were significantly affected by the applications except for the total anthocyanin amount. The amount of protein, phenolic and flavonoid was found to be lower in the control compared to all applications. Antioxidant activities were measured with four different methods and the effects of the applications on CEAC and DPPH activity were found to be insignificant, while the effects on CUPRAC and FRAP were significant. All applications exhibited higher CUPRAC and FRAP activity compared to the control. Application, storage period and their interactions showed significant effects on the activity of all enzymes. Antioxidant enzymes CAT and SOD were significantly increased especially with CuNP+PUT application, while oxidative enzymes H2O2 and MDA were reduced by applications. In conclusion, this study showed that putrescine alone can be effective in postharvest storage of grapes, but the antioxidant system is more activated when combined with nanocopper. In addition, considering that copper is antimicrobial and therefore decay will be reduced, the combined application of CuNP+PUT was evaluated as a promising approach for postharvest storage of grapes.