Effect of Ultrasound‐Assisted Osmotic Pretreatment on Selected Physicochemical Attributes and Antioxidant Characteristics of Soft‐Dried Longan

Ultrasound‐assisted osmotic pretreatment has emerged as an effective strategy to enhance mass transfer and improve quality retention in soft‐dried fruit products. However, integrated evaluation of processing parameters and storage‐related changes in soft‐dried longan remains limited. This study investigated the effects of osmotic solution composition, ultrasound conditions, drying temperature, and storage on selected physicochemical attributes and antioxidant characteristics of soft‐dried longan ( Dimocarpus longan Lour.). Key indicators, including vitamin C, reducing and total sugars, total polyphenols, and DPPH radical scavenging activity, were analyzed to assess bioactive retention and quality changes. The investigated processing conditions, including 30% sucrose, 0.2%–0.4% citric acid, 0.2%–0.3% CaCl 2 , an ultrasound temperature of approximately 50°C, a treatment time of 20 min, an ultrasound power of 225–300 W, and a drying temperature of 45°C, showed comparatively better retention of structural and antioxidant characteristics within the tested range. Excessive ultrasound intensity, prolonged exposure, or elevated temperatures accelerated degradation of heat‐ and oxidation‐sensitive compounds. During storage, vitamin C and total polyphenols declined progressively, whereas refrigerated conditions significantly slowed quality deterioration compared with room temperature. These findings suggest that ultrasound‐assisted osmotic pretreatment combined with controlled drying and appropriate storage conditions may contribute to better retention of selected bioactive compounds and quality‐related attributes of soft‐dried longan. The results provide useful insights into storage‐related quality changes in soft‐dried longan.