Abstract
This study examined the influence of the food matrix composition on the chemical and colloidal stability as well as functionality of curcumin-loaded lipid nanoparticles with different lipid phase state (liquid vs. solid). For this, lipid nanoparticles formulated with medium-chain triglycerides (MCT), MCT with glyceryl stearate (MCT + GS), or coconut oil (CNUT) were dispersed into aqueous phases with varying degrees of complexity, being aqueous solutions of the main components of cloudy apple juice. The physicochemical characteristics and colloidal stability of curcumin-loaded lipid nanoparticles was not dramatically affected by its incorporation into the food matrix. Remarkably, curcumin retention (%) of lipid nanoparticles was higher when they were incorporated into the food matrix. In general, lipid nanoparticles after incorporation into a cloudy apple juice exhibited a slower lipid hydrolysis during in vitro digestion conditions compared to the lipid nanoparticles alone, yet reaching to higher free fatty release at the end of the intestinal phase. Moreover, lipid nanoparticles in cloudy apple juice demonstrated significantly higher curcumin bioaccessibility compared to the lipid nanoparticles alone. Among the lipid-phase formulations, solid lipid nanoparticles (SLNs) exhibited greater curcumin bioaccessibility than liquid lipid nanoemulsions (LLNs), with CNUT-SLN achieving the highest bioaccessibility (39.10 ± 0.61%) in cloudy apple juice. These results highlight the critical roles of lipid phase state and food matrix composition in determining the digestive fate and bioaccessibility of encapsulated lipophilic compounds. The study supports the potential of lipid nanoparticles and fruit-based beverages as promising platforms for delivering curcumin and other hydrophobic bioactives in functional food applications.
Highlights
- Cloudy apple juice improved curcumin retention in lipid nanoparticles.
- Cloudy apple juice slows lipid hydrolysis but yields higher fatty acid release.
- Solid lipid nanoparticles gave the highest curcumin bioaccessibility (39%).
Introduction
Curcumin is a lipophilic bioactive compound of the polyphenol family, present in turmeric (Curcuma longa) with low molecular weight that has antioxidant anticancer and antimicrobial activities (Sharifi-Rad et al., 2020). However, its use as a nutraceutical ingredient in foods is limited due to its poor water-solubility and fast oxidation after exposure to high temperatures, light and oxygen. Moreover, it presents poor stability and absorption during digestive condition, which limits its functionality in foods (González-Peña et al., 2023; McClements, 2021). The protection of bioactive compounds is crucial for the development of functional foods that provide health benefits beyond basic nutrition (Parsi et al., 2025; Zamani Ghaleshahi & Rajabzadeh, 2020). Lipid-based nanoparticles is an encapsulation technique for incorporating bioactive compounds into aqueous food products, enhancing their solubility, stability, bioavailability, and absorption by providing a protective matrix (Ayoub et al., 2019; Rao & McClements, 2011). Lipid nanoparticle functionality is mainly influenced by physicochemical properties such as size, surface area, morphology (Parsi et al., 2025; Ridolfo et al., 2021), composition and lipid phase state (Chang & McClements, 2014). In this context, lipid-based nanoparticles can be divided to liquid lipid nanoemulsions (LLNs) and solid lipid nanoparticles (SLNs), which are formulated with a liquid lipid or a solid lipid phase, respectively(Mall et al., 2025; Salvia-Trujillo et al., 2013). LLNs and SLNs consist of lipids, surfactants and water and are characterized by their small particle size, high surface area, and high kinetic stability (Mason et al., 2006).
SLNs are formulated with a solid lipid core, which has shown to improve the chemical stability of lipophilic compound by limiting diffusion into the aqueous phase compared to liquid lipid systems (Salvia-Trujillo et al., 2018), because the solid matrix restricts molecular mobility and acts as a physical barrier against degradative agents. However, SLNs made from pure lipids with a narrow melting range formed highly ordered crystals. This perfect lattice provided little space for the encapsulated bioactive compound and tended to expel it over time, causing instability and morphological changes (de Abreu Martins et al., 2021). To solve this, SLNs can be fabricated from lipids with a broad melting range, which creates a more disordered crystal structure that improves both bioactive compounds loading and stability (Qian et al., 2013; Weiss et al., 2008). Therefore, studying the influence of the lipid phase composition of SLN on the stability of encapsulated bioactive compounds is important to determine their potential functional properties. Moreover, emulsified solid lipids present a delayed lipolysis when compared with liquid oils in terms of lipid digestibility (Nik et al., 2012; Salvia-Trujillo et al., 2019). Modulating lipid digestibility is important for managing health conditions like obesity by controlling nutrient absorption, and for enhancing the benefits of food by delivering nutrients or lipophilic compounds in a targeted way (Guo et al., 2017; Kupikowska-Stobba et al., 2025). The reason for this behaviour has been attributed to the hindered adsorption of lipase on lipid-water interfaces, which may provide opportunities to control the lipid digestibility of such delivery systems (Infantes-Garcia et al., 2022).
Despite lipid-based nanoparticles are proven to be effective in delivering bioactive compounds for food fortification, their stability and functionality when incorporated into complex food matrices remain underexplored. Recently, the incorporation of nano-delivery systems in complex beverage matrices, such as fruit juices, has gained significant attention as a strategy to enrich them in lipophilic bioactives with improved stability (Gonçalves et al., 2022; Otchere et al., 2023). However, formulating these systems for commercial beverages remains challenging, as the presence of antioxidants and macromolecules in complex food matrices, such as polysaccharides, can influence both the stability of the system and the bioaccessibility of encapsulated bioactive compounds (Molet-Rodríguez, Torcello-Gómez, et al., 2023; Molet-Rodríguez, Turmo-Ibarz, et al., 2021).Bioactive compounds are highly sensitive to environmental factors such as pH and light oxygen, and temperature (Chai et al., 2018). In this way, Zhang et al. (2020) demonstrated that the physical and chemical stability of lipid nanoemulsions incorporated into apple juice is highly dependent on matrix-specific conditions, such as pH. Similarly, the pH and viscosity of the food matrix can impact the solubility and absorption of bioactive compounds in the gastrointestinal tract. In addition, the presence of fats and other lipids in the food matrix can influence the bioavailability of bioactive by promoting its solubilization and absorption in the intestinal lumen (Molet-Rodríguez, Ramezani, et al., 2023; Ramezani et al., 2024). Hence, it is important to carefully consider the lipid-based nanoparticles formulation and processing conditions to optimize its incorporation into food systems.
In this context, the present study aimed at evaluating how food matrix composition influences the stability of lipid-based nanoparticles, whether lipid phase is in liquid, solid form and its subsequent impact on the stability of encapsulated curcumin as a representative lipophilic bioactive compound. In order to study the influence of each constituent in cloudy apple juice, apple juice-main components solutions containing fructose, malic acid, and pectin were also formulated. Then, the individual components effect on the physical and functional characteristics of lipid nanoparticles was assessed by measuring particle size, zeta potential, interfacial tension, colloidal stability and curcumin retention (at 25 and 4 °C). Moreover, this study had the additional objective of evaluating the behaviour of cloudy apple juice enriched with curcumin-loaded lipid nanoparticles under simulated in vitro gastrointestinal conditions in terms of the lipid digestibility as free fatty acid (FFA) release during small intestinal conditions and curcumin bioaccessibility.
Download the full article as PDF here Incorporation of curcumin-loaded lipid nanoparticles into a cloudy apple juice
or continue reading here
Materials
The lipid phases used in this study consisted of coconut oil (CNUT), purchased from a local supermarket (Lleida, Spain), and medium-chain triglycerides (MCT oil (Mygliol® 812 N)), ( Hamburg, Germany) with glyceryl stearate (GS (Imwitor® 491)) from IOI Oleochemical GmbH (Hamburg, Germany). The primary surfactant was polyoxyethylene-sorbitan monooleate (Tween 80) from Lab Scharlab (Barcelona, Spain). The encapsulated active compound, curcumin (from Curcuma longa), was sourced from Sigma-Aldrich (Darmstadt, Germany).
The food matrix components included cloudy apple juice, kindly provided by Indulleida S.A. (Lleida, Spain), and ingredients for apple juice-main component solutions: apple pectin (Sigma-Aldrich, Darmstadt, Germany), d-fructose (Scharlau Chemie S.A., Barcelona, Spain), and DL-malic acid (>99%, Acros Organics, Belgium).
Reagents for the in vitro digestion study included bovine bile (B3883), porcine pepsin (77160), and porcine pancreatin (P7545), were supplied by Sigma-Aldrich (St. Louis, MO, USA). Other chemicals used were hexane (Scharlab, Barcelona, Spain), ethanol (Fisher Scientific, Loughborough, UK), and sodium azide (Acros Organics, Geel, Belgium). All aqueous solutions and emulsions were prepared with ultrapure Milli-Q water obtained from a Millipore filtration system (Merck, Darmstadt, Germany).
Anali Parsi, Ana Turmo-Ibarz, Laura Salvia-Trujillo, Olga Martín-Belloso, Incorporation of curcumin-loaded lipid nanoparticles into a cloudy apple juice: study of the chemical and colloidal stability, in vitro digestibility and bioaccessibility, Food Research International, Volume 238, 2026, 119476, ISSN 0963-9969, https://doi.org/10.1016/j.foodres.2026.119476.
Read more interesting articles on curcumin here:
