Ultrasound-Assisted Osmotic Pretreatment of Myrtle (Myrtus communis L.) Berries with Grape Molasses: Impacts on Convective Drying Quality

Myrtle berries are rich in bioactive phenolics and volatile terpenes and have potential for use in functional food products. However, the combined application of grape molasses and ultrasound as a pretreatment before drying has received limited attention. This study characterized fresh ‘Yakup’ myrtle berries as baseline material and explored the drying behavior and measured quality attributes of berries subjected to twelve pretreatments combining grape molasses or water, ultrasound-assisted or static immersion, and treatment durations of 30, 45, or 60 min. Pretreated and untreated fruits were dried by forced-air convection at 60, 75, and 90 °C. Dried samples were evaluated for antioxidant activity, total phenolic content (TPC), total anthocyanin content (TAC), sugar composition, and drying behavior. The shortest observed drying times at 60 and 75 °C occurred after ultrasound treatment in grape molasses for 30 and 45 min, respectively, whereas static immersion in grape molasses for 60 min and the untreated control showed the shortest drying times at 90 °C. Static immersion in grape molasses for 45 min showed the highest measured TPC at 60 °C (1353.47 mg GAE/100 g dw), while the untreated control showed the highest TPC at 75 and 90 °C and the highest TAC at all three temperatures. The treatment showing the highest total sugar concentration also differed with drying temperature. Thus, no single pretreatment consistently maximized all measured attributes. The findings identify condition-specific candidate strategies rather than a universally superior pretreatment. Because each treatment–temperature combination was represented by one drying tray and the triplicate compositional determinations were analytical rather than independent process replicates, the comparisons are descriptive and require confirmation in independently replicated processing trials. Complete pretreatment mass balances are also required before water loss, solid gain, solute uptake, or true compound retention can be quantified. Looking ahead, studies can be conducted that include sensory and economic evaluations by creating customized pretreatment protocols for industrial applications.