Decoupling Amplitude, Energy Input and Contact Time in the Ultrasound‐Assisted Extraction of Ascophyllum nodosum Bioactives

ABSTRACT

Ultrasound‐assisted extraction (UAE) is promising for recovering seaweed bioactives, but confounding amplitude/power, energy input, and treatment time complicates mechanistic interpretation and cross‐study comparison. We decoupled amplitude/power from energy input during aqueous UAE of Ascophyllum nodosum , evaluating amplitude, energy input, contact time/mixing, temperature control, and biomass loading. A probe‐type system provided direct energy control (50–500 kJ; 31–313 J mL ^{− 1} ), with controlled bulk temperature and total solid–liquid contact time. Responses included gravimetric solubilization, soluble protein and carbohydrate, total phenolic/phlorotannin content, and antioxidant capacity. At 50 kJ, amplitude variation from 25%–100% (56–416 W) had no significant effects. At 275 and 500 kJ, only phenolic extraction and DPPH activity showed modest amplitude dependence. Total energy input dominated: increasing energy enhanced solubilization and soluble protein extraction but reduced phenolic content and antioxidant capacity, consistent with ultrasound‐induced degradation at extended sonication energies. Additional stirring and cooling had no significant effects under the tested conditions, whereas biomass loading strongly affected all responses except solubilization. Amplitude alone is therefore insufficient to characterize UAE performance. Decoupling amplitude from energy input and contact time identifies energy density, specific energy, and treatment time as recommended standardization metrics for meaningful cross‐technology comparisons.