# Microencapsulation of Anthocyanins--Critical Review of Techniques and Wall Materials
## 2 Microencapsulation Techniques
### Physicochemical Methods  
#### 2.3.1 Emulsions and Double Emulsions  
Emulsions are often used as a medium to enable the wide use of various components that do not dissolve in an aqueous environment. Emulsions are an excellent means of distributing functional substances in aqueous media, protecting them from degradation and greatly influencing their release control. One of the continuously developed areas in the field of emulsion application is Pickering emulsions. The most frequently claimed advantage of this type of emulsion is that no surfactants are needed, droplets are avoided, and it is very stable. For example, [PERSON] et al. [80] showed that the combination of gliadin and proanthocyanins as the stabilizer for Pickering emulsions enhanced the antioxidant activity of the emulsion. In a study by [PERSON] et al. [81], an anthocyanin complex with black rice and soy protein isolate was used to produce Pickering emulsions. The results showed that the emulsions stabilized by the complex of anthocyanin nanoparticles and soy protein isolate had very high stability while reducing the oxidation of soybean oil, which was the core material in the emulsion. Interestingly, the slower digestion rate of Pickering emulsions was also demonstrated, making it possible to use this type of product in food with a reduced caloric value. Another type of emulsion that is often encountered when using anthocyanins is the double emulsion, most often of the water-in-oil-in-water (W/O/W) type. A double emulsion of water-in-oil-in-water (W/O/W) is a microencapsulation procedure, which is used to gain easily controlled release as a carrier for hydrophilic active substances, such as anthocyanins and procyanidin [82]. A double emulsion is, however, not stable, and it is challenging to preserve its composition. Complex coaervation was used in previous works to enhance the double emulsion's efficacy through the electrostatic attraction of oppositely charged biopolymers, allowing for complex coaervated surfaces with reduced solubilization and isolation of the liquid-liquid process [6]. There are various studies involving the application of emulsions for the microencapsulation of anthocyanins. One study used a combination of polyphenols and anthocyanins derived from blueberry that was stabilized using whey proteins to produce double emulsions. The results showed that it is possible to produce optimal emulsions using high-pressure homogenization [83]. Another study focused on the use of guar gum and a double emulsion to enhance anthocyanins' thermal stability. The impacts of various guar gum concentrations on color stability, anthocyanin concentration, and antioxidant capacity were assessed after ten days of storage at 40 \({}^{\circ}\)C in the presence of light. According to the researchers, the addition of guar gum had a substantial impact on the samples' antioxidant potential. The double emulsion demonstrated a high encapsulation efficiency and kinetic stability under the conditions tested in this research and shielded anthocyanin molecules from degradation [84]. Another study examined the properties and in vitro release kinetics of anthocyanin-rich microcapsules that were prepared by spraying and freeze drying complex coaervated double emulsions using gelatin-acacia gum (GE-AG) and chitosan-carboxymethylcellulose (CS-CMC). The results indicated that microcapsules might be used to load anthocyanins as a nutraceutical with a managed release requirement [85]. The application of sodium carboxymethylcellulose (CMCNa) to boost the stability and bioavailability of anthocyanin-containing W1/O/W2 emulsions was presented in another study. The emulsions were produced using ultrasound technology, with the inner aqueous phase containing polyglycerol polyricinoleate and the outer aqueous phase containing lecithin and Tween 20. The processes were physiochemically defined over time, and their activity was examined under simulated gastrointestinal conditions.