Ultrasound- and LED-mediated modulation of drying behaviour, surface morphology, phenolic composition, and volatile...

Goji berry (Lycium barbarum L.) is highly perishable and requires dehydration for preservation, creating challenges for retaining nutritional and functional quality. This study compared blue, yellow, and red light-emitting diode (LED) treatment followed by a common ultrasound pretreatment and far-infrared drying at 70, 80, and 90 °C. Treatment-dependent effects were evaluated for drying behaviour, apparent activation parameters, antioxidant and enzymatic responses, phenolic composition, endpoint surface morphology, and volatile profiles. In the drying profiles at the 90 °C chamber, US-BL90 and US-YL90 reached the final moisture criterion at approximately 300 min, whereas US-Con90 reached it at approximately 540 min. Within the empirical-model comparison, the Hii and Midilli models yielded the strongest goodness-of-fit statistics; the derived apparent activation energies ranged from 23.43 to 31.28 kJ/mol. DPPH radical-scavenging activity was highest in US-Con80 (0.94 mM TE/g), while total phenolic content was highest in US-Con90 (2.42 mg GAE/100 g). US-YL70 showed the highest summed concentration of quantified phenolic compounds among the processed samples. Browning index was highest in US-RL80 (0.61). SEM showed treatment-dependent endpoint external surface features, including surface openings, fissures, compact regions, and differences in wax-like surface features. The applied HS-SPME/GC-MS workflow identified 82 volatile compounds and showed treatment-dependent differences in the measured volatile profiles. Overall, LED treatment within a common ultrasound-assisted far-infrared drying sequence modified dehydration behaviour and multiple quality attributes, but no treatment produced uniformly beneficial responses across all measured outcomes.