## 1 Introduction  
Eugenol (C\({}_{10}\)H\({}_{12}\)O\({}_{2}\)) which is a phenylpropanol group consisting of an allyl chain-substituted by guaiaicol is a major bioactive compound that has a concentration of 45-90% in clove. This essential oil has shown many pharmacological uses due to its antibacterial, antifungal, antiplasmodial, antivirus, anthelminit, anti-inflammatory, analgesic, and antioxidant activities [1]. However, eugenol has limited applications, because of its volatility, slight solubility in water, and ease of damage when exposed to high temperatures, air, and light. Nevertheless, encapsulation technology has been used to overcome these problems and to improve the utilization of essential oils as pharmaceuticals and food ingredients. Some benefits of encapsulating essential oils include increasing stability, protecting active compounds from interaction with other ingredients, increasing the activity or functional properties, and decreasing volatility and toxicity [2; 3]. In addition, encapsulation protects active compounds from oxidation, masks flavor, allows controlled release, and increases bioavailability and efficacy [4; 5; 6].  
The benefit of encapsulation is achieved by using an appropriate polymer matrix as a wall material. Some factors affecting the retention and release of active compounds from the film include the type of polymer, the preparation method, the interaction between polymeric and active compounds, and the environment [7; 8]. Generally, protein and carbohydrates are good combinations for wall materials for encapsulation [9]. Whey protein (WP) as a protein and maltodextrin (MD) as a polysaccharide are frequently used as a matrix in essential oil encapsulation, emulsifying agents, and stabilizers [10; 11]. Moreover, protein-conjugated polysaccharides are better emulsifiers than proteins or polysaccharides alone. The difference between the present work and previous studies lies in the type of whey protein used. The whey protein used in this study was derived from bovine milk and had a protein content of 7-11%, whereas the isolates had a protein content of more than 90%.  
No research has been conducted on double-layer eugenol encapsulation using a whey protein-maltodextrin (WPMD) conjugate as the first layer and the effect of chitosan as the second layer. Generally, double-layer encapsulation is formed using layer-by-layer electrostatic deposition of polyelectrolytes on oppositely charged surfaces and is processed by emulsification and homogenization [12; 13]. The advantages of a double-layer system are better stability against environmental stress than a single layer [14] and the controlled release of active compounds [15].  
Chitosan was chosen as the second layer in consideration of its characteristics and the findings of some related research. Previous studies have confirmed that a multilayer oil-in-water emulsion containing lecithin, chitosan, and pectin made through the layer-by-layer method exhibited good stability to aggregation [16]. Several studies on the effectiveness of chitosan as an encapsulating agent and its profile release have been carried out by some researchers [17; 18; 19]. Furthermore, according to [PERSON] et al. [20], chitosan has the ability to form ionic or covalent bonds with crosslinking agents and form a network in which the active compounds can be maintained. These properties are highly advantageous and necessary for controlling the release of active compounds.  
The objectives of this study were (1) to develop a new formulation of biopolymers using the double-layer method for eugenol encapsulation and (2) to investigate the effect of different eugenol and chitosan concentrations on emulsification, encapsulation performance, and the physical properties of spray-dried powders. In addition, the kinetics and mechanism of eugenol release from microcapsules were also evaluated.