Innovative Use of Kiwano Cloud Point Extract in Bioactive Nanoemulsion Development

Kiwano (Cucumis metuliferus) peel, although rich in carotenoids and polyphenols with notable antioxidant capacity, is still an underused resource. This study explored its valorization through cloud point extraction (CPE) and its direct integration into nanoemulsion systems. The innovative aspect lies in reusing the CPE as a stabilizing agent, creating a closed process that efficiently incorporates bioactive compounds. In the first phase, oil-in-water nanoemulsions were prepared with sunflower oil, Tween 80, and different polysaccharides (pectin, carboxymethyl cellulose-CMC, and their blends). Their stability, droplet size, surface charge, rheological, mechanical, and barrier properties were thoroughly assessed. CMC-based formulation displayed the most favorable characteristics, particularly strong stability and tensile strength, and was selected as the optimal system. In the second phase, kiwano peel extract was incorporated at three concentrations (5, 10, and 15 wt%). While extract addition lowered tensile strength, it improved elongation at break, suggesting a plasticizing effect. Moreover, extract-loaded emulsions exhibited smaller droplets, high stability, and significantly enhanced antioxidant activity compared to unloaded systems. These results demonstrate that kiwano peel can be sustainably valorized through CPE and integrated into nanoemulsions, offering promising bioactive formulations for future applications in food science.