W/O/W Emulsions as a Strategy to Preserve NADES-Derived Annatto Carotenoids and Enhance the Functional Properties of Potato Starch-Based Active Packaging Films

Abstract

This study investigated the use of a water-in-oil-in-water (W/O/W) double emulsion to encapsulate a natural deep eutectic solvent (NADES)-based annatto (Bixa orellana L.) seed extract and incorporate it into potato starch-based films. The aim was to improve the stability and functionality of the extract compared with its direct addition to the starch matrix. The physicochemical properties of the W/O and W/O/W emulsions were first characterized, followed by the evaluation of the resulting films. The droplet size of the W/O/W emulsion (1.21 ± 0.03 μm) was larger than that of the W/O emulsion (0.42 ± 0.03 μm). The W/O/W emulsion exhibited a high encapsulation efficiency (95.5 ± 0.5%) and maintained a substantial fraction of the antioxidant activity of the encapsulated extract. When incorporated into potato starch films, the W/O/W emulsion reduced the moisture content by 46.7% and water vapor permeability by 52.2%, from 1.84 ± 0.41 to 0.88 ± 0.02 g mm m–2 h–1 kPa–1. The film containing the double emulsion (DE-5%) exhibited a tensile strength of 21.84 ± 0.97 MPa and showed antioxidant activity comparable to the free extract, with a measured value of 4.88 ± 0.28 mg TE g–1 of annatto seed. In addition, the ultraviolet–visible (UV–vis) light barrier properties were improved. Microstructural, X-ray diffraction (XRD), and thermal analyses indicated that the W/O/W emulsion modified film morphology and reduced matrix crystallinity without impairing film formation. Overall, the results indicate that W/O/W emulsions are a promising strategy to enhance the protection of NADES-derived bioactive compounds and improve the structural and functional properties of potato starch-based films for active biodegradable packaging applications.