Ultrasound-Extracted Lycopene in Whole-Spirulina-Stabilized Submicron Emulsions: Formulation, Stability, and Retention

Tomato-processing residues present a viable secondary source of lycopene; however, the hydrophobic nature and chemical instability of this carotenoid limit its direct integration into aqueous products. This study employed ultrasound-assisted extraction to obtain a lycopene-rich extract from tomato by-products, subsequently incorporating it into oil-in-water emulsions stabilized by whole Spirulina biomass. The carrier, comprising 9.5 wt.% pumpkin seed oil and 0.5 wt.% linseed oil, was produced using rotor–stator homogenization followed by probe sonication. A formulation with 2.71 wt.% Spirulina, treated for 813 s, was selected. Pulsed extraction resulted in 1.05 ± 0.08 mg of apparent lycopene equivalents per gram of dry by-product. The UV-Vis method demonstrated linearity from 0.5 to 5.0 µg mL−1, with detection and quantification limits of 0.08 and 0.24 µg mL−1, respectively, and a recovery rate of 96.2 ± 3.1% from spiked emulsion. The incorporation of lycopene did not significantly affect the Z-average diameter, polydispersity, or 30-day physical stability. After 28 days, lycopene retention was 78.4 ± 3.2% at 4 °C and 49.6 ± 4.1% at 25 °C, with a significant interaction between time and temperature.