Mechanisms of Browning Inhibition and Quality Preservation in Apples: The Role of Tragacanth Gum as a Postharvest Coating

Postharvest browning is a major factor contributing to quality loss and reduced shelf life in apple (Malus domestica) fruits, leading to diminished consumer appeal and marketability. The enzymatic browning process, primarily driven by polyphenol oxidase (PPO) and peroxidase (POD) activity, significantly affects the texture, color, and overall quality of apples during storage. The present study investigates the potential of tragacanth gum, a natural polysaccharide, as an edible coating to mitigate postharvest browning and preserve the sensory attributes of apples during refrigerated storage. Apples were treated with a 1% (w/v) tragacanth gum solution and stored at 0°C under controlled atmosphere (CA) conditions with 90–95% relative humidity for 20 days. The effects of the coating on browning were evaluated through visual inspection, color measurements (L*, a*, and b* values), and enzymatic activity assays for PPO and POD, which are key enzymes responsible for oxidative browning. In addition, sensory attributes such as firmness, texture, aroma, flavor, and overall acceptability were assessed by a trained panel. The results demonstrated that tragacanth gum coatings effectively reduced the rate of browning in the apples, as evidenced by improved color retention and a significant reduction in PPO and POD activity compared to the untreated control. The treated apples maintained a more vibrant appearance, with less discoloration and a longer-lasting fresh look. Furthermore, the tragacanth gum-coated apples exhibited enhanced firmness and texture with no significant loss of aroma and flavor, resulting in improved overall sensory quality. The overall acceptability scores of the treated apples were higher than those of untreated controls, indicating that the coating preserved the sensory appeal of the fruit. These findings suggest that tragacanth gum acts as a natural and effective postharvest treatment to delay browning, maintain texture, and enhance flavor, thereby improving the marketability and shelf life of apples. This study highlights the potential of tragacanth gum as an eco-friendly, non-toxic alternative to synthetic coatings, offering a promising strategy for postharvest management and quality preservation in apples under refrigerated and controlled-atmosphere storage conditions.