Antioxidant Response of Sweet Cherry Cultivars with Contrastive Surface Pitting Susceptibility During Cold Storage

Surface pitting is a physiological disorder characterized by depressions on the fruit surface, caused by subepidermal cell collapse and exacerbated during cold storage. This study evaluated antioxidant responses and cell wall disassembly in sweet cherry cultivars exhibiting contrasting susceptibility to surface pitting. Four cultivars were evaluated over two growing seasons under controlled cold storage and shelf-life conditions, with pitting experimentally induced. Surface pitting severity was strongly genotype-dependent. After 15 d at 1 °C in the first season, pitting severity was higher in ‘Sweetheart’ and ‘Lapins’ (2.4 and 1.9, respectively) than in ‘Regina’ (0.6), while in the second season, ‘Sweetheart’ reached the highest damage at shelf life (3.5) and ‘Santina’ remained low (0.8), confirming lower susceptibility in ‘Regina’ and ‘Santina’ than in ‘Sweetheart’ and ‘Lapins’. Cell wall-related traits and pectinolytic enzyme activities exhibited strong seasonal variability and were not consistently associated with pitting incidence. In contrast, resistant cultivars exhibited higher non-enzymatic antioxidant levels. Total phenolic content reached 4.1 ± 0.4 mg g⁻¹ in ‘Regina’ at the end of storage, while antioxidant capacity reached 51.5 ± 3.3% DPPH inhibition, up to 2-fold higher than susceptible cultivars. Enzymatic antioxidant activities were influenced by cultivar and season and showed limited association with pitting development. These results indicate that phenolic-based non-enzymatic antioxidant capacity plays a central role in conferring tolerance to surface pitting in sweet cherry during cold storage.