Mechanical modification and ultrasound-assisted osmotic dehydration for mass transfer intensification during blueberry convective drying

This study investigated the use of mechanical modification (MM) and ultrasound-assisted osmotic dehydration (OD + US) as process-intensification strategies before convective drying of blueberries (Vaccinium corymbosum L.). MM (cutting and perforation) were combined with osmotic dehydration at 40-60°Brix, with ultrasound applied at 37 kHz and 33.86 W/L to enhance mass transfer. Peleg modeling revealed that ultrasound increased water loss and solute gain during OD, attributed to cavitation-induced microchannel formation and enhanced solvent penetration through the berry skin. Although MM facilitated initial mass transfer, ultrasound promoted additional structural disruption, particularly in cut samples, as evidenced by viscoelastic weakening and altered rehydration behavior. Drying kinetics, described by the Page model, showed that pre-treatments reduced the time required to reach 12% moisture by over 30%, indicating effective process intensification. Bioactive compounds decreased after drying; however, ultrasound-assisted treatments retained higher levels after OD compared to non-sonicated samples, suggesting reduced oxidative degradation during mass transfer. Sorption isotherms fitted to the GAB model enabled shelf-life prediction, demonstrating extended stability under aluminum laminate packaging. The combined perforation and OD + US treatment at 50°Brix provided the most favorable balance between drying efficiency and quality retention. Overall, results demonstrate that ultrasound acoustic cavitation combined with MM and OD enhances mass transfer, modifies microstructure, and improves dehydration performance in blueberries.