W/O/W emulsions with gelled aqueous and oil phases: Construction, characterization, and their effect on enhancing the stress resistance of Lactobacillus plantarum and Streptococcus thermophilus.

Influence of Oil Phase and Emulsifier on Single and Double Emulsions: Formation, Stability, Encapsulation Efficiency, and Antioxidant Activity

Chitosan–cinnamaldehyde–whey protein concentrate stabilized W1/O/W2 double emulsion for co-encapsulation of tea polyphenols and β-carotene

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

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.

Colloidal stabilization of oil-in-water emulsions in aqueous partially saponified poly(vinyl alcohol) solutions of low concentration as continuous phase.

Water-soluble polymers (WSPs) are normally used as thickeners for colloidal stabilization of oil-in-water (O/W) emulsions because the creaming of O/W emulsions is prevented by increasing the viscosity of continuous phase. We examine here the effect of WSPs such as polyethylene glycol (PEG), polyvinylpyrrolidone (PVP) and partially saponified poly(vinyl alcohol) (ps-PVA) on the colloidal stabilization of O/W emulsions prepared in aqueous solutions of low concentration WSP (0.5 wt%) as continuous phase. We found that the colloidal stability of WSP-O/W emulsions prepared by mixing soybean oil (SOY) and aqueous ps-PVA solution with a rotor-stator homogenizer (ps-PVA-SOY/W emulsion) was remarkably high compared to other WSPs-SOY/W emulsions, even if the viscosity of aqueous ps-PVA solutions that we applied in this work was almost same with that of water. In particular, the ps-PVA with lower saponification degree was more effective for colloidal stabilization of O/W emulsions than other WSPs. The higher colloidal stability of ps-PVA-SOY/W emulsions prepared using ps-PVA with lower saponification degree is most likely due to the decrease in interfacial tension between oil and water by ps-PVA with lower saponification degree, and the resulting formation of smaller-sized oil droplets.

W₁/O/W₂ double emulsions based on sodium alginate internal gelation: A hierarchical strategy to enhance emulsion stability and probiotic viability.

The sensitivity of probiotics to environmental stress significantly restricts their widespread application. Here, a novel W₁/O/W₂ double emulsion was constructed via sodium alginate-mediated internal gelation, and its physicochemical properties and protective efficacy for Lactobacillus plantarum were evaluated. Results showed that internal gelation significantly remodeled the emulsion microstructure, creating a compact internal assembly positively correlated with gelation intensity. Compared to the non-gelled control, the gelled emulsions exhibited superior physical, storage, and centrifugal stability, with the 1% alginate gelation intensity achieving the optimal stabilization effect. Rheological data demonstrated that the sodium alginate gel network formed in the internal aqueous phase greatly increased emulsion viscosity. It also modulated the viscoelastic behavior and built a robust physical barrier. This reinforced internal microenvironment markedly improved emulsion stability and effectively mitigated external stress, thereby significantly enhancing the viability of the entrapped probiotics. Furthermore, to further strengthen this protective effect, microcapsules fabricated via freeze-drying exhibited a uniform and dense honeycomb-like cross-linked network, characterized by excellent rehydration properties, solubility, and low moisture content. These solid microcapsules provided enhanced resistance against environmental stress, further improving the storage stability of the probiotics. In conclusion, the hierarchical strategy combining sodium alginate-mediated internal gelation and microencapsulation offered a robust engineering approach for the high-efficiency preservation of probiotics.

Curdlan as a heat-irreversible gel wall material in electrostatic spray-dried solid/oil/water probiotic microcapsules: Thermal resistance and storage stability.

In this study, to develop a robust probiotic delivery system, high molecular weight 1,3-β-D-glucan curdlan gum (CUR) was employed as a functional wall material. It was combined with whey protein isolate and high oleic sunflower oil to prepare solid/oil/water (S/O/W) emulsion microcapsules using electrostatic spray drying (ESD) technology. Additionally, pectin and high oleic sunflower oil were utilized as functional wall materials. All the microcapsules exhibited low water content (3.66%-5.04%) and water activity (aw 0.178-0.230), which is beneficial for long-term storage stability. Following drying, the survival rate of probiotics in each treatment group exceeded 90%. It is worth noting that the microcapsules containing 5% CUR exhibit the most effective overall protective effect: following heat treatments of 63 °C for 30 min and 75 °C for 10 min, the loss of viable bacteria was only 1.18 and 1.39 Log CFU/g, respectively. After 12 weeks of storage at 4 °C and 25 °C, the survival rates were maintained at 93% and 66%, respectively. Its excellent performance is attributed to the fact that CUR can form a dense gel network structure at high temperatures, which effectively blocks heat transfer and oxygen penetration. Scanning electron microscopy and Fourier-transform infrared spectroscopy confirmed that microcapsules containing 5% CUR form a relatively dense physical barrier and maintain structural integrity. The above results demonstrate that incorporating CUR into a S/O/W emulsion system, combined with ESD technology, is a promising strategy for wall materials to enhance the thermal tolerance and shelf-life stability of probiotic microcapsules.