Effectiveness of Gum Arabic, Potassium Salts and Their Incorporation in The Control of Postharvest Diseases and Maintaining Quality of ‘Washington’ Navel Oranges during Long Term Cold Storage

Document Type : Original Article


Horticulture Department, Faculty of Agriculture, Tanta university, Tanta , Egypt


Edible coating of gum arabic (GA) and food preservatives with antifungal properties included potassium sorbate (PS) and potassium bicarbonate (PB) were evaluated on ‘Washington’ navel oranges during long term cold storage in 2016 and 2017 seasons. Orange fruits were dipped for three minutes into the following treatments: distilled water and used for untreated fruits (control), 0.2% imazalil (IMZ) and used as a commercial fungicide, 10% GA, 2% PS, 2% PB, 0.2% IMZ incorporated with 10% GA, 2% PS incorporated with 10% GA and 2% PB incorporated with 10% GA. After that, all treatments stored at 5±1˚C and 90±5% relative humidity (RH) for ten weeks followed by one week as a shelf life period at 18-23°C and 55±5% RH. The changes in physical and chemical characteristics of orange fruits were determined every two weeks intervals of cold storage periods followed by one week shelf life. In general, all postharvest treatments effectively reduced fruit weight loss, controlled decay incidence, decreased size of lesion surface diameter, increased marketable fruit percentage, maintained rind firmness and retained fruit visual appearance as compared to untreated oranges and treated with IMZ during storage period. Moreover, these applications significantly decreased loss of fruit juice, ascorbic acid, titratable acidity (TA) as well as significantly slowed the accumulation of total soluble solids (TSS) and TSS/TA ratio. In addition, these applications increased total phenolic content and enhanced total antioxidant capacity of oranges as compared to untreated fruits. In particular, 2% PS or 2% PB incorporated with 10% GA coating applications were the most effective in this aspect in comparison to the other treated and untreated fruits. Thus, these applications showed an easy and inexpensive approach as a suitable alternative to the currently adopted IMZ application for controlling postharvest decay and suppressing the deterioration of physical and chemical characteristics of ‘Washington’ navel oranges during long term storage at low temperature.