The preservation of fruit quality and the extension of shelf life are commonly achieved through the utilization of cold storage. However, the challenge arises from the susceptibility of lemon fruit to chilling due to its tropical and subtropical origin. In this study, a predictive model was developed using Response Surface Methodology (RSM) to explore the impact of melatonin at various concentrations (50, 100, 500 µM) and dipping times (5, 10, 15 min) as independent variables, along with storage days (25, 50, 75 days), on postharvest attributes of Lisbon lemon during cold storage (maintained at 3 ± 0.5 °C with an additional 5 days at 20 °C). The RSM model demonstrates high accuracy, as indicated by satisfactory R2 and values, signifying significant fitness (p > 0.05). Nevertheless, it is crucial to note the study’s limitations, such as the lack of thorough consideration of variations in environmental conditions. The robust predictive capabilities of the RSM model parameters validate its efficacy. The results emphasize the substantial impact of melatonin on lemon fruit quality parameters, enhancing overall visual quality, phenol content, and antioxidant capacity, while concurrently mitigating water loss, electrolyte leakage, and malondialdehyde production. Using the utility function method, the optimal preservation condition for lemon fruit is determined to be a 436 μM melatonin treatment combined with a 15-min dipping time. These findings underscore the potential of melatonin in preserving the postharvest quality of lemon fruit, providing a promising approach for extending shelf life and enhancing the nutritional value of this essential citrus crop.

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