# Microencapsulation of Anthocyanins--Critical Review of Techniques and Wall Materials
## 2 Microencapsulation Techniques
### Chemical Methods  
The formation of inclusion complexes is considered to be an encapsulation method in which a bioactive guest compound or part of the molecule can fit into a cavity-bearing host molecule via van der Waals forces, hydrogen bonding, or hydrophobic interactions [70]. Cyclodext (CDs) are the most widely used materials for forming inclusion complexes with an extensive range of organic substances. CDs are a series of naturally accruing cyclic D-glucopyranose oligomers possessing six (\(\alpha\)-CD), seven (\(\beta\)-CD), or eight (\(\gamma\)-CD) glucopyranose units linked by \(\alpha\)-(1,4)-glucoside bonds, leading to the formation of a torus-shaped ring structure. Depending on the type of CDs, they have different cavity diameters, which are approximately 6, 8, and 10 A for \(\alpha\)-CD, \(\beta\)-CD, and \(\gamma\)-CD, respectively. Nevertheless, the depth of the cavities for the three CDs is the same (\(\approx\)7.8 A) (Figure 3) [71]. The internal part of the CDs has nonpolar nature, making them favorable for hydrophobic components, whereas the hydrophilic exterior surface provides polarity and accelerates the water-solubility of guest molecules [72]. The formation of inclusion complexes and their stability largely depends on the shape/size fit between the guest molecule and the host CD. Consequently, various sorts of CDs would present different inclusion complexation capacities with the same guest molecule, leading to dramatically different biological and physicochemical properties [73]. Among all the CDs, \(\beta\)-CD is the most prevalent material used in the food sector due to its availability, safety, and fair price. The diameter of the \(\beta\)-CD cavity is nearly 7.8 A, and the molecular size of natural anthocyanin is about 6.3 \(\times\) 12 A; thus, benzopyrylium or phenyl moiety of the anthocyanin can form a complex with \(\beta\)-CD [74]. In other words, the cavity and hollow molecular shape of the CDs make them ideal candidates to decrease anthocyanins loss by preserving them from polymerization, oxidation, and degradation reactions. This characteristic can also provide thermal stability and controlled release properties [5]. In this direction, [PERSON] et al. [75] showed that \(\beta\)-CD could prolong the release behavior of cornelian cherry up to 50% over the first two hours. Furthermore, the degradation temperature shifted from 219 \({}^{\circ}\)C for free cornelian cherry to 225 \({}^{\circ}\)C for cornelian \(\beta\)-CD/cornelian cherry. [PERSON] et al. [76] examined the light stability of \(\beta\)-CD microcapsules containing mulberry anthocyanins and displayed 1.36 times higher anthocyanin retention for microcapsules than nonencapsulated anthocyanins. Additionally, the microcapsules' storage stability was nearly 9% and 7% higher than using solely anthocyanin within 28 days of storage under unpackaged and vacuum packaged conditions, respectively. [PERSON] et al. [77] also demonstrated the efficiency of \(\beta\)-CD at reducing the blackberry pigments\({}^{\prime}\) degradation rate under a simulated gastrointestinal environment. [PERSON] et al. [78] compared the EE, color, and morphological properties of saffron-anthocyanin-loaded \(\beta\)-CD and \(\beta\)-glucan and observed superior values for the EE and a whiter powder in the case of \(\beta\)-CD. In terms of the size and morphology, \(\beta\)-glucan formed spherical capsules that were smaller in size, while \(\beta\)-CD formed particles with uneven shapes and various orientations.  
>100 g/100 mL. They observed a drastic reduction in the thermal and photodegradation rate constants of anthocyanins while applying CA instead of \(\beta\)-CD, even at high concentrations.