Optimization and Characterization of an O/W Emulsion Based on Coccoloba uvifera Seed Protein Loaded with Extract of Randia monantha

The study aimed to optimize an oil-in-water emulsion loaded with the antioxidant extract of Randia monantha using Coccoloba uvifera seed protein (CUSP) as emulsifier and ultrasound-assisted processing. Response surface methodology (RSM) was employed to evaluate the effects of protein concentration (2, 3, and 4%), oil amount (5, 15, and 25%), and ultrasound duration (3, 5, and 7 min) on the polydispersity index (PDI) and droplet size. A total of 21 mg of extract was added to each formulation. The optimal conditions were a 3% protein concentration, 20% oil content, and 7 min of ultrasound. Under these conditions, the emulsion showed low PDI (1.88), D[3,2] (1.11 µm), and D[4,3] (1.60 µm). It remained stable at 4 °C for 15 days within a pH range of 6−10, with NaCl concentrations < 200 mM and at temperatures between 25 and 50 °C. Thermal analysis of the emulsion revealed endothermic transitions and decomposition events at higher temperatures, achieving 100% entrapment efficiency and ~83% photoprotection for the extract. This plant protein stabilizes the extract at the oil/water interface, enhancing thermal stability and protecting against photodamage. These qualities are vital in the food industry for preserving thermolabile compounds. The emulsion can enhance antioxidant properties in semi-solid foods or be spray-dried into a powder for functional formulations.