Combined Anti-Browning Mechanism of Pre-Cutting High Oxygen Treatment and Post-Cutting Withania somnifera Extract Treatment on Fresh-Cut Apples.

Fresh-cut apples are highly prone to browning during processing and storage. This long-standing problem will cause huge economic losses and restrict the commercial development potential of the fresh-cut fruit industry. In this study, Fuji apples were used as test materials to explore the inhibitory effect and anti-oxidant mechanism of pre-cutting high oxygen treatment (90% O2, 3 h) combined with post-cutting Withania somnifera extract immersion on the browning of fresh-cut apples. Through the determination of physiological and biochemical indexes and proteomics analysis, the effects of different treatments on the nutritional quality, reactive oxygen species metabolism, membrane lipid peroxidation, anti-oxidant enzyme activity and related protein expression of fresh-cut apples were systematically evaluated. The results showed that after 14 days of storage, the combined treatment group had the lowest browning index of 41.29% and the highest whiteness index of 60.35%, and its color protection effect was significantly better than that of single high oxygen treatment or single extract treatment. The combined treatment could increase the total phenol content to 6.45 mg/g after 7 days of storage, and increase the DPPH free radical scavenging rate to 0.60% after 14 days of storage, significantly enhancing the anti-oxidant capacity. Meanwhile, the combined treatment could maintain higher activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD), and maintain the malondialdehyde content at a low level of 0.06 nmol/g after 14 days of storage, effectively delaying the process of membrane lipid peroxidation. However, adverse results were also observed in the study, including the rebound of superoxide anion level (28.16 nmol/g) after 14 days of storage, the highest accumulation of H2O2 during the whole storage period, and the significant increase in polyphenol oxidase (PPO) activity (151.14 IU/L) after 14 days of storage, indicating an elevated browning risk under prolonged storage. Proteomics analysis revealed that the combined treatment regulated multiple metabolic pathways, including the up-regulating of glutathione metabolism and pentose phosphate pathway to enhance reactive oxygen species scavenging capacity, as well as the modulation of fatty acid metabolism to preserve cell membrane integrity. Despite the above limitations, the overall browning inhibitory effect of the combined treatment is still better than that of a single treatment, but its pro-oxidant effect and long-term reactive oxygen species regulation effect still need to be further optimized. In summary, pre-cutting high oxygen treatment combined with post-cutting Withania somnifera extract treatment is an effective anti-browning strategy for fresh-cut apples, which can provide a theoretical basis for the development of natural and efficient fresh-cut fruit and vegetable preservation technology.