This work aimed at obtaining an optimized formation procedure of water-in-oil-in-water (W1/O/W2) double emulsions as potential templates to carry hydrophilic (eg. chlorophyllin; CHL) and/or hydrophobic (eg. lemongrass essential oil; LG-EO) active compounds. As a first step, the impact of the hydrophobic surfactant (ie. Span 80 or PGPR), sodium alginate or NaCl concentration as well as the homogenization method (ie. high-shear homogenization, ultrasonication or microfluidization) on the particle size of the primary W1/O emulsions was evaluated. The inner phase (W1/O) formulated with PGPR (4% w/w) and sodium alginate (2% w/w) with NaCl (0.05M) and treated by highshear homogenization (11,000 rpm, 5 min) presented the smallest particle size (d[4;3] ≈ 0.51 µm). As a second step, the primary W1/O emulsion was subsequently dispersed in a secondary aqueous phase (W2) at varying hydrophilic surfactant (ie. lecithin or Tween 20), sodium alginate or NaCl concentrations and magnetic stirring rate (rpm and time) to obtain double emulsions (W1/O/W2). The formation of stable W1/O/W2 emulsions with d[4;3] of 7 µm was achieved with the use of lecithin (2% w/w), sodium alginate (2% w/w) with NaCl (0.05M) and treated by low-intensity UT homogenization (5,600 rpm, 2 min) followed by 24h of magnetic stirring. The incorporation of CHL and LG-EO in the inner aqueous phase and lipid phase respectively did not change the double emulsion characteristics. Overall, this study presents an effective two-step optimized procedure to form stable double emulsions as potential delivery systems for functional compounds.

In the last few decades, lifestyle changes and the awareness of the importance of a balanced diet have led the population to increase the consumption of beverages based on fruit juices and/or vegetables. Fruit and vegetables contain health-related compounds that can impact on physiological processes, thus reducing the risk of certain diseases and improving the overall health status. Consumer demand for more appealing and tasting beverages has also increased. In this sense, fortification of beverages with health-related ingredients and/or flavors arises as a potential strategy for the development of new beverage-based products. Nevertheless, most of those compounds are not soluble in water, thus their incorporation in aqueous food systems, such as beverages, requires an emulsification step. Beverage emulsions are concentrated emulsified systems designed to be further diluted and/or incorporated in beverages and drinks as carriers of water insoluble ingredients. This review article aims at discussing the main key aspects of beverage emulsion formulation and their colloidal stability after being added to complex food systems.

This review aims at presenting recent advancements on the design of novel emulsion-based nanostructures for an effective incorporation of active ingredients into foods. The specific characteristics of nanoemulsions, solid lipid nanoparticles, and double emulsions are highlighted. Nanoemulsions are oil-in-water emulsion with droplet sizes below 200 nm that are known to present high stability over time. Moreover, due to their reduced droplet size and therefore maximized active surface area, they are capable of enhancing the interactions with biological systems, such as foods. For instance, nanoemulsions present an improved functionality of active ingredients and a fast digestibility under gastrointestinal conditions leading to an optimal absorption of bioactive ingredients contained within them. Solid lipid nanoparticles are particularly effective for protecting lipophilic active ingredients in their lipid inner core, since the crystalline state of the lipid droplets can reduce the oxidative and degradation processes occurring in aqueous systems. Nevertheless, their formulation should be carefully selected in order to obtain the desired effect. Lastly, double emulsions are defined as emulsions of an emulsion. Therefore, their formation consists on the formation of a primary water-inoil emulsion and its subsequent further emulsification in a secondary aqueous system. This allows the encapsulation of hydrophilic active compounds in the inner aqueous phase. Their stabilization remains as a scientific challenge yet they present promising applications. The main key aspects for the formation, stabilization and their behavior during gastrointestinal conditions are addressed.

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Water-in-oil-in-water (W1/O/W2) emulsions are emulsion-based systems where the dispersed phase is an emulsion itself, offering great potential for the encapsulation of hydrophilic bioactive compounds. However, their formation and stabilization is still a challenge mainly due to water migration, which could be reduced by lipid phase gelation. This study aimed to assess the impact of lipid phase state being liquid or gelled using glyceryl stearate (GS) at 1% (w/w) as well as the hydrophilic emulsifier (T80: Tween 80 or lecithin) and the oil type (MCT:medium chain triglyceride or corn oil (CO) as long chain triglyceride) on the formation and stabilization of chlorophyllin W1/O/W2 emulsions. Their colloidal stability against temperature and light exposure conditions was evaluated. Gelling both lipid phases (MCT and CO) rendered smaller W1 droplets during the first emulsification step, followed by formation of W1/O/W2 emulsions with smaller W1/O droplet size and more stable against clarification. The stability of W1/O/W2 emulsions was sensitive to a temperature increase, which might be related to the lower gelling degree of the lipid phase at higher temperatures. This study provides valuable insight for the formation and stabilization of W1/O/W2 emulsions with gelled lipid phases as delivery systems of hydrophilic bioactive compounds under common food storage conditions.

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