Preharvest Application of Oxalic Acid to ‘Calabacita’ Fresh Figs: Effects on Physicochemical and Antioxidant Profile During Cold Storage

Fresh figs are a highly perishable fruit with a very limited shelf life. Consequently, the development of innovative strategies at both the preharvest and postharvest stages is essential to enhance their quality and extend their shelf life. This study aimed to evaluate the postharvest performance of fresh figs (cv. Calabacita) treated preharvest with oxalic acid (OA) via foliar spraying at 1.2 L per tree at two concentrations (1 and 2 mM), applied either twice or three times. Figs were harvested at commercial maturity and stored for 10 days at 1 °C and 90% relative humidity in darkness, with sampling carried out at 0, 3, 7 and 10 days. At each sampling point, physiological, physicochemical, and bioactive parameters were assessed, and an analysis of variance was performed to determine differences among OA treatments. The findings showed that the effectiveness of OA depended on the number of applications, with two preharvest sprays providing the most favourable outcomes. OA at 2 mM significantly reduced weight loss, respiration rate, and ethylene production compared with controls and increased titratable acidity. Furthermore, all OA treatments enhanced the antioxidant activity of the fruit, improving both enzymatic and non-enzymatic antioxidant activity, as well as total phenolic content. This suggests improved stress tolerance supported by lower cell wall oxidation at the end of cold storage. In conclusion, two preharvest applications of oxalic acid effectively contribute to maintaining fruit quality and extending the storability of fresh figs during cold storage.