## 1 Introduction  
Essential oils (EOs) are frequently used to provide flavour and aroma to a wide range of food and cosmetics and are increasingly used as antimicrobial agents and feed additives [1, 2, 3, 4, 5]. EOs are highly volatile and mostly insoluble in water, and prone to degradation by exposure to oxygen, light, water and heat. Microencapsulation, wherein one material or mixture of materials (i.e., core or active ingredient) is coated with or entrapped within another wall material or shell, is an established technique to protect active ingredients such as EOs against the external environment. A wide range of microencapsulation methods have been used for encapsulation of flavours and aromas--see, for example, the review by [PERSON] [6] and references therein. Peppermint oil is one of the most commonly used essential oils, with applications in food, perfumery, pharmaceutical and flavouring products [7]. Microencapsulation of peppermint oil has been performed using, for example, complex coacervation and spray drying [8, 9, 10], electrospray alginate capsules [7, 11], entrapment in cellulose nanocrystals [12], and free radical interfacial polymerization [13]. Additionally, microfluidics [14] and especially supercritical fluid (SCF) techniques [15, 16] are emerging as alternative methods for micro- and nanoencapsulation of volatile ingredients. While spray drying is by far the most common microencapsulation method for protecting volatile ingredients such as essential oils from degradation, complex coaervation is an attractive and scalable alternative method offering higher payloads (up to 99%), better hydrothermal resistance and controlled release properties [17; 18]. Complex coaervation is a liquid-liquid phase separation phenomenon that occurs upon mixing oppositely charged weak polyelectrolytes, typically a protein and a polysaccharide (see, e.g., the excellent review by [PERSON] et al. [19] for a thorough description). Microcapsules produced by complex coaervation form core-shell structures, either mononuclear, polynuclear or aggregated \"grape\" coaervates depending on parameters such as the Reynolds number during capsule formation and hardening, and the cooling/hardening rate [20]. As the core is protected from water in the external phase, complex coaervation is well suited for encapsulation of hydrophobic substances such as essential oils. The protein-polysaccharide combination of gelatin and gum Acacia remains the most widely studied set of wall materials for microencapsulation of essential oils via complex coaervation [1; 17; 18]. However, any oppositely charged polyelectrolyte pair can in principle be used, provided the charge density on the polymeric species allows for liquid-liquid phase separation--see, for example, de Kruif [19] and references therein for a non-exhaustive overview of combinations of wall materials reported in the literature. For microencapsulation of peppermint oil, reported wall materials for complex coaervation typically use gelatin as the protein, combined with either gum Acacia [8], pectin [10] or mixtures containing chitosan [9]. One inherent limitation of complex coaervation is that the process is limited to a relatively narrow solvent-rich corner of the ternary phase diagram. For example, for the system gelatin-gum Acacia, the concentration of both polymers has to be below 8% (_w:w_) in order for coaervation to occur [20]. Consequently, there is often a need for post-processing in the form of, for example, freeze drying or spray drying in order to reach sufficiently high concentrations of active ingredients as well as to provide further protection from hydrothermal degradation. However, this also entails additional thermal gradients and shear forces, necessitating crosslinking of the capsules. In food and nutraceutical applications, there is a severely limited choice of crosslinking agents regarded as safe, with the enzyme transglutaminase being the most widely used [6].