Assessment of the protective potential of coated microparticles in a fluidized bed against the simulated digestion

Introduction

Microencapsulation has been widely used in the food industry to encapsulate ingredients, such as flavors (Alvarenga Botrel et al., 2012; Fernandes et al., 2014), unsaturated oils (Carneiro et al., 2013; de França et al., 2024), antioxidant substances (Ballesteros et al., 2017; Da Silva et al., 2013; Flores et al., 2014), and probiotics (Arepally & Goswami, 2019; Sharma et al., 2022). This technique involves enclosing a sensitive or functional core, called active or filler material, with an encapsulating agent known as the wall material (de França et al., 2024; Reineccius, 2004). Microencapsulation provides protection to sensitive ingredients against environmental conditions, such as humidity, oxygen, pH, and temperature (Mardani et al., 2024; Turchiuli et al., 2005), while also facilitating the handling and incorporation of controlled release mechanisms. The food industry has been one of the most prominent in the production of microparticles, with usage regarding the improvement of sensory aspects, mainly related to texture, smell, and their perception, as well as heat resistance, chemical preservation, controlled release, and protection of active compounds (Lalarukh Hussain et al., 2025).

Among the various encapsulation methods, spray drying is the most commonly used because it is an economical and flexible process with widely available equipment, resulting in good retention of volatile compounds and stability of the final product, as well as the production of high-quality particles (Carneiro et al., 2013; Fernandes et al., 2014; Mardani et al., 2024). Additionally, it allows for the controlled release of these compounds in the gastrointestinal tract, increasing their bioavailability and efficacy in specific physiological processes (Di Giorgio et al., 2019; Eratte et al., 2018) because the active compound can be protected by a defensive barrier against adverse conditions during storage and transit through the digestive system (Lalarukh Hussain et al., 2025). However, this technique has limitations such as the potential for low encapsulation efficiency, which can result in active compounds being exposed on the particle surface. Wu et al. (2014) reported the use of wall materials (maltodextrin, gum Arabic, κ-carrageenan, and β-cyclodextrin), inlet temperatures (from 150 to 230 °C) and core/wall ratios (from 1:5 to 1:25) on the encapsulation of sulforaphane. Regarding encapsulation efficiency, they verified that gum Arabic was the best wall material under the experimental conditions, promoting a higher encapsulation efficiency of 39.8 % than the other encapsulating materials. The authors reported an inverse effect of temperature on encapsulation efficiency. Finally, regarding the core/wall ratio, there was little variation in the results, from 37.3 to 39.5 %. Tupuna et al. (2018) also reported relatively low values of encapsulation efficiency when norbixin was encapsulated with blends of maltodextrin and gum Arabic as wall material. They reported values of 22.52 % for a formulation of only maltodextrin following an increase in encapsulation efficiency with an increase in the amount of gum Arabic in the formulation, reaching 50.02 % for the case of gum Arabic only. The limitations of the spray drying technique are also related to the formation of porous structures, leading to a greater migration of oxygen and volatile compounds through the particle structure. Consequently, there may be increased degradation or loss by volatilization of the encapsulated compounds during food processing, storage, or distribution (Reineccius & Yan, 2016).

To mitigate these negative effects, several strategies for improving the barrier properties of microparticles are being employed, such as stabilization of emulsions by multiple layers of oppositely charged biopolymers, especially for the protection of lipophilic compounds (de França et al., 2024; Fang et al., 2019; Shaw et al., 2007); the use of proteins and their protein hydrolysates as encapsulating agents in combination with maltodextrin (Galves et al., 2021; Gomes and Kurozawa, 2021, Gomes and Kurozawa, 2024); and coating of microparticles obtained by spray drying in a fluidized bed (Anwar et al., 2010; Buffo et al., 2002; Fuchs et al., 2006; Sun et al., 2013; Watano et al., 2004). Furthermore, in the case of oils and lipophilic bioactive compounds, microencapsulation is strongly influenced by the emulsifying properties of wall materials. These materials must facilitate proper emulsification to ensure that the formed emulsion maintains sufficient stability to withstand the atomization process during drying. This, in turn, reduces the surface oil content and increases encapsulation efficiency (Gharsallaoui et al., 2007; Jafari et al., 2008).
Fluidized-bed coating involves the application of thin layers of coating material onto dry particles with exceptionally low density and/or small size (Suhag et al., 2020). Studies have shown that, in addition to masking the bad taste and odor of compounds, the fluidized bed coating technique can improve the stability, controlled release, and bioavailability of active compounds such as antioxidants, vitamins, and omega-3 fatty acids during digestion (Dewettinck & Huyghebaert, 1998). Additionally, the coating layer can enhance food preservation by preventing microbial contamination, extending the shelf life, and acting as a moisture barrier. It can also provide antioxidant properties, be biodegradable, enable targeted nutrient delivery, improve appearance and structural integrity, and enhance handling through its physical and mechanical properties (Gupta et al., 2024). In some cases, the coating can also reduce the premature release of active compounds in the stomach, protecting them from degradation, and increasing their delivery to the intestine. Moreover, fluidized bed coatings can enable the incorporation of active compounds into foods and food products, making them more functional and healthier (Abbas et al., 2012; Brandelli et al., 2017; Desai & Jin Park, 2005; Galvão et al., 2020). In other cases, this technique can improve moisture barrier properties, flowability, and taste. Fluidized bed coating allows the creation of single or multiple layers for the production of tunable particles for oral delivery, including extended or delayed release, and enteric coating (Yan & Kim, 2024).

Some authors have reported particle production via spray drying followed by fluidized bed coating, primarily for the protection of flavors. Buffo et al. (2002) evaluated how agglomeration by fluidized bed processing may affect the properties of encapsulated spray-dried flavors, and concluded that agglomeration resulted in some flavor loss from all matrices studied, with the greatest losses occurring in the most volatile components. Sun et al. (2013) evaluated the fluidized bed coating of spray-dried menthol particles with gelatin, starch sodium octenyl succinate, and ethyl cellulose aqueous dispersion. Controlled release was assessed by Static Headspace Analysis, concluding that coating powders prepared using a fluidized bed were better than non-coated particles for controlling the release of menthol in water. Fuchs et al. (2006) investigated the separate and combined use of spray drying and fluidized bed agglomeration of vegetable oil in a matrix made of two usual protective supports, maltodextrin and gum acacia. They assessed the stability of the powders against oxidation and concluded that the three processes represent an efficient way to prepare formulations containing encapsulated oil in the support of acacia gum and maltodextrin, with reduced oil losses. To the best of our knowledge, there are no studies in the literature that have investigated in vitro digestion and the release of free fatty acids from spray-dried and fluidized bed-coated linseed oil microparticles.

Therefore, the objective of this work was to coat spray-dried linseed oil microparticles in a fluidized bed, evaluate the effectiveness of the coating process in producing coated particles through microscopy and Raman spectroscopy analysis, and assess the coating efficiency against the in vitro digestion process.

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Materials

The bioactive material encapsulated was linseed oil (LO) (Vital Âtman, Brazil). Whey protein isolate (WPI) (90 % protein, ShafiGlucoChem, Pakistan) and maltodextrin (MD) (10DE, MOR-REX® 1910, Ingredion, USA) were used as wall materials. The coating solution consisted of an aqueous solution of hydroxypropyl methylcellulose (HPMC) 1 % w/w (Ingredion, USA). Microcrystalline cellulose (CMC) (Microcel®, Blanver Farmoquímica, Brazil), with density and mean particle sizes of 1.5485 ± 0.0010 g/cm³ .

Raul Favaro Nascimento, Pedro Renann Lopes de França, Matheus Alves Ferreira, Louise Emy Kurozawa,
Assessment of the protective potential of coated microparticles in a fluidized bed against the simulated digestion,
Food Research International, Volume 208, 2025, 116273, ISSN 0963-9969, https://doi.org/10.1016/j.foodres.2025.116273.

Read also our introduction article on Microcrystalline Cellulose here: