Post-Harvest Washing Modulates Phenolic Content, Antioxidant Capacity, and Sugar Profile of Sukkari Date Fruits (Phoenix dactylifera L.)

Post-harvest washing is widely applied to improve fruit safety; however, its effects on the biochemical quality of date fruits remain insufficiently understood. This study evaluated how different washing solutions, applied at varying concentrations (2–8%) and volumes (1–2 L), affect total phenolic content (TPC), antioxidant capacity (AOC), and sugar composition in Sukkari date fruits. Washing treatments have induced significant but non-uniform changes across all measured parameters. TPC ranged from 8.43 to 11.65 mg GAE g−1 FW, compared with 11.11 mg GAE g−1 FW in the control, while total sugars varied between 59.81 and 64.77 g 100 g−1 FW relative to 62.36 g 100 g−1 FW in the control. Water-based treatments lowered several phenolic and antioxidant measurements, while sugar responses varied with water type and application intensity; possible leaching or moisture-related effects require direct verification. In contrast, chemically active treatments exhibited concentration- and treatment-dependent responses. Organic acids generally maintained or slightly increased measured values, whereas oxidative and salt-based treatments showed variable, non-linear patterns depending on treatment intensity. DPPH capacity did not consistently correspond with TPC, indicating that TPC alone did not explain variation in the measured radical-scavenging response. Overall, the results demonstrate treatment-dependent associations between washing conditions and the measured biochemical quality indices; the underlying mechanisms require direct investigation. These findings highlight the importance of optimizing washing conditions to balance microbial safety with preserving nutritional and functional quality in date fruits.