Revealing the Critical Impact of Cold Storage Duration on the Browning and Antioxidant Dynamics in the Rind of Jackfruit ( Artocarpus heterophyllus Cv. J33)

Jackfruit (Artocarpus heterophyllus cv. J33) is an emerging export fruit valued for its flavor, nutrition, and market potential. However, prolonged cold storage often causes rind browning, leading to quality deterioration and postharvest losses. While previous postharvest studies have primarily focused on flesh deterioration, the enzymatic and non-enzymatic biochemical mechanisms driving cold-induced browning in jackfruit rind during export have not been comprehensively elucidated. This is the first study that provides evidence linking PPO-driven phenolic degradation with oxidative stress dynamics in jackfruit rind during cold storage. Cold storage at 12 ± 1°C for four weeks triggered oxidative stress in the jackfruit rind, leading to a 97% reduction in total phenolic content and a sharp decline in antioxidant capacity. Among five phenolics, quinic acid, chlorogenic acid, and catechin peaked after one week before decreasing, whereas L-phenylalanine and shikimic acid accumulated progressively. Polyphenol oxidase (PPO) activity increased by 48% over four weeks, coinciding with marked reductions in superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase. Concurrently, malondialdehyde levels rose and hydrogen peroxide fluctuated, confirming oxidative imbalance, with week 2 of cold storage identified as the critical threshold where antioxidant defenses collapsed, leading to PPO-mediated phenolic oxidation and accelerated rind browning. By utilizing multiple linear regression and multivariate analysis to simultaneously track these markers, this study establishes a comprehensive model (R2 = 0.997) proving that rind browning is primarily driven by PPO-mediated oxidation (p < .0001) under declining antioxidant defenses (e.g. APX, r = -0.690). The findings clarify the biochemical basis of rind browning that provide potential intervention strategies for horticulture and export industry to develop targeted postharvest treatments by preserving non-enzymatic antioxidants, specifically TPC and TFC to mitigate commercial postharvest losses,