Effect of gum arabic coating functionalized with thymol and salicylic acid on non-pathogenic quality attributes of plums (‘Angeleno’) during shelf life

Thymol and salicylic acid have been reported to control fungal proliferation and act as elicitors in various fruit. While the antifungal properties of these bioactive agents are widely known, their effects on other quality attributes require further investigation. The effectiveness of thymol and salicylic acid in gum arabic composite coatings to maintain non-pathogenic quality attributes of plum was investigated, focusing on delayed senescence and shrivel. Gum arabic (GA, 0.5% w/v) was formulated with thymol (Thy) and salicylic acid (SA), each at 0, 1, 2 and 4 mM, and fludioxonil (Flu) was included as a positive control. Quality assessments were performed for weight loss, firmness, total soluble solids, and shrivel over a 15-day storage period at shelf life conditions (23±2°C and 75±5% RH). GA composite exhibited varying effects on fruit quality. For instance, the treatment had the lowest weight loss (5.51%) compared to control and Flu, both with 7.37% weight loss. At the end of the storage period, GA-1 mM SA delayed fruit softening, with 2.54 N firmness compared to control fruit (1.44 N). However, all treatments, except GA-2 mM SA, were significantly lower in total soluble solids (TSS) compared to the control (16.76 °Brix). Fruit treated with Flu had the highest shrivel incidence (25%) at the end of the 15-day storage period, while GA maintained a significantly lower shrivel incidence (6.67%). Overall, despite the benefits offered by thymol and salicylic acid in effectively controlling decay in previous studies, only gum arabic alone proved sufficient in maintaining non-pathogenic related quality attributes, including alleviating weight loss and shrivel, and delay ripening in fruit in this study.