Pre-Harvest Application of Multi-Walled Carbon Nanotubes Improves the Antioxidant Capacity of ‘Flame Seedless’ Grapes during Storage

Abstract

As a widely distributed fruit, grapes are susceptible to oxidative damage during storage and transportation, resulting in declining quality and commodity value. This study aimed to investigate the effects of preharvest application of different concentrations of multi-walled carbon nanotubes (MWCNTs) on the postharvest quality of ‘Flame Seedless’ grapes. The results showed that low-concentration (25 and 50 mg L−1) MWCNTs treatments maintained the comprehensive quality index, firmness, soluble sugar, titratable acid, pH value, and ascorbic acid (AsA) content of grapes. MWCNTs at 25 and 50 mg L−1 increased the activities of peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), and ascorbic acid (APX). Furthermore, MWCNTs reduced the malondialdehyde (MDA) content and decreased the accumulation of excessive reactive oxygen species (ROS) in grape peel and pulp tissues. In addition, transmission electron microscopy (TEM) images demonstrated that MWCNTs were absorbed by parenchymal cells in the grape peel and pulp through the epidermal cell layer. MWCNTs with a specific concentration can be used as a new inducer for the biosynthesis of antioxidants to reduce oxidative damage in grapes during storage.