Ultrasound- and LED-mediated modulation of drying behaviour, surface morphology, phenolic composition, and volatile profiles in goji berries

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.

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