The current trend in food consumption values nutritious foods, with fewer synthetic additives and minimal processing (Beristaín-Bauza et al., 2018). Therefore, the food industry has increased its efforts to replace these additives with natural compounds to meet the growing demand for healthy products (Ferraz et al., 2021).

Natural antimicrobials (NA) are considered an alternative to chemical preservatives, which are increasingly associated with negative health consequences, such as allergies, toxicity, carcinogenicity, as well as environmental problems related to the long time it takes for degradation (Cava-Roda, Taboada-Rodríguez, López-Gómez, Martínez-Hernández, & Marín-Iniesta, 2021). Essential oils (EOs) are natural bioactive compounds extracted from plants, which have good antibacterial, antifungal, antiviral and antioxidant activities (Qin, Tang, Chen, & Xie, 2024). Moreover, many EOs have been recognized as safe natural flavoring materials for food applications (Hebishy, Collette, Iheozor-Ejiofor, & Onarinde, 2022). The main essential oils are obtained from certified crops, such as lavender, thyme, cinnamon, oregano, basil, or rosemary (Salanță & Cropotova, 2022).

Cinnamaldehyde (3-phenyl-2-propenal, CIN), a hydrophobic aromatic aldehyde, is the main component of cinnamon bark (Zhao et al., 2022). CIN has demonstrated a broad-spectrum antimicrobial activity against bacteria, yeasts, and moulds and is used as flavoring in some foods because of its distinct aroma profile (Chen et al., 2018). Vanillin (4-hydroxy-3-methoxybenzaldehyde, VA) is the main component of vanilla beans. It has been widely used as a flavoring agent in foods and beverages for decades across the world, but emerging scientific evidence suggests that it has several biological activities as well, such as anticancer, antidiabetic, antioxidant, antibacterial and antidepressant properties (Olatunde, Mohammed, Ibrahim, Tajuddeen, & Shuaibu, 2022; Orizano-Ponce, Sepúlveda, Ortiz-Viedma, & Char, 2022).

Despite all the advantages that EOs and their bioactive compounds have, their application is still limited by the drawbacks such as hydrophobicity, high volatility, and strong flavor (Zhu, Li, Cui, & Lin, 2021). New approaches for the incorporation of these hydrophobic compounds into aqueous-based foods are being investigated, such as developing new delivery encapsulated systems for EOs that would enable a widespread use in foods with improved efficacy (Liao, Dumas, Ghnimi, Elaissari, & Gharsallaoui, 2021; Sharma, Mann, Pothuraju, Sharma, & Kumar, 2022). Oil-in-water (O/W) emulsions are promising encapsulated systems that not only enhance the miscibility of the compound, but also minimize the direct impact of bioactive compounds on sensory attributes, and also improve the chemical stability of these active compounds by protecting them from environmental factors (such as oxygen, light, moisture, and pH) during food processing (Ferraz et al., 2021).

The whey protein concentrate (WPC) is obtained by concentration and subsequent dehydration of the by-product of the cheese factory, contributing to the sustainability of the industry. It consists of three principal proteins: β-lactoglobulin, α-lactalbumin and bovine serum albumin, among others (Boeve & Joye, 2020). Whey protein is a surface-active protein often used in the formulation of emulsions due to its various functional and technological properties such as the ability to form gels, emulsions, foams, and films, also for its cost effectiveness and wide availability (Amjadi, Almasi, Ghadertaj, & Mehryar, 2021; Li & Zhu, 2021). Proteins could adsorb droplets to the oil-water interface, lowering the interfacial tension and retarding droplet coalescence by forming a protective membrane around the oil droplets (Tian et al., 2023). The stability of the microparticles is crucial for food processing and storage, so understanding and improving the properties of the encapsulated system is of great importance to the food industry (Dapueto, Troncoso, Mella, & Zúñiga, 2019).

Considering all the above, the main objective of this work was to formulate and characterize microcapsules of cinnamaldehyde and vanillin using whey protein concentrate as encapsulating agent with the aim to enhance their miscibility in high moisture foods. Likewise, some properties of the encapsulated systems such as droplet size, stability, release over time, etc., were evaluated. Additionally, the antimicrobial activity of the free natural antimicrobials and the corresponding microcapsules was assessed in a high moisture food system, such as a whey protein beverage.