Pre-storage oxalic acid treatment inhibits postharvest browning symptoms and maintains quality of abiu (Pouteria caimito) fruit

The effect of exogenous oxalic acid (OA) treatment on browning and postharvest quality of abiu fruit was evaluated during the storage period. Abiu fruit was soaked in water (control), 5 mM oxalic acid (OA5), and 10 mM oxalic acid (OA10) for 10 min and air-dried, and then stored in an ambient room (28 +/- 1 degrees C and 80 +/- 5% RH) for 12 days. The results showed the peel browning in control, and the OA5-treated reached 30% on day-6 of the storage and day-12 storage for the OA10-treated. In addition, the browning symptoms in abiu pulp reached 30% on day-3, day-6, and day-9 storage, for control, OA5, and OA10, respectively. The exogenous OA10 treatment in abiu fruit could suppress the oxidation of phenolic compounds and inhibit an increase in polyphenol oxidase (PPO) enzyme activity and malondialdehyde (MDA) content during storage. In addition, applying the OA10-treated in abiu fruit could reduce 1-aminocyclopropane-1-carboxylic (ACC) concentration, ethylene production, respiration rate, and delay the occurrence of the climacteric peak. The exogenous OA10 treatment in abiu fruit could also reduce fresh weight loss, titratable acidity (TA), ascorbic acid, and maintain fruit firmness during storage. Therefore, the exogenous OA10 treatment could be considered an appropriate treatment to delay browning and preserve the quality of the abiu fruit.