# Microencapsulation of Anthocyanins--Critical Review of Techniques and Wall Materials
## 2 Microencapsulation Techniques
### Physical Methods
#### 2.1.1 Spray Drying
Wall materials that meet the requirements and are thus suitable for spray drying microencapsulation include:* Polysaccharides (starch, chitosan, pectin, natural gums, uncilages, cellulose, and their derivatives). * Animal and plant-based proteins (whey protein, caseinate, gelatin, and soy protein). Generally, the contribution of polysaccharides is larger than that from proteins for microencapsulation purposes using spray drying. The reasons why polysaccharides are extensively considered as suitable wall materials are their high holding capacity, low viscosity, excellent solubility, and emulsifying properties [6]. Maltodextrin has been widely used as a wall material for the microencapsulation of anthocyanins using SD. In this direction, dextrose equivalent (DE) has a pivotal role in the process yield of spray drying since a higher degree of DE produces a large proportion of powders with a wetted surface and a high wall material thickness that sticks to the chamber wall and diminishes the process yield [27]. Furthermore, anthocyanins become more heat-sensitive while applying higher DE due to the increased number of open sides of the molecule, facilitating the oxidation of aldehydes and ultimately the production of a deformed structure [36]. [PERSON] and [PERSON] [37] developed microcapsules with maltodextrin with 6, 19, 21, and 33 DE containing anthocyanins from Garcia India. It was revealed that the anthocyanin content increased from 325 mg/100g with a DE of 6 to 430 mg/100 g with a DE of 21; nevertheless, both parameters dropped as DE rose from 21 to 33. Apart from DE, the concentration of maltodextrin can also influence the EE. [PERSON] et al. [29] examined the effects of maltodextrin's concentration on the properties of microcapsules containing blueberry anthocyanins. They found EE percentages ranging from roughly 74 to 85%, with the best EE reported for the highest concentration of maltodextrin (18%) at all temperatures. In most of the studies, the highest EE and stability were achieved by using a combination of wall materials [31; 32; 33; 38]. For instance, [PERSON] et al. [39] applied a standard formulation of maltodextrin and hi-maize starch combined with gum Arabic, inulin, and both gum Arabic and inulin for the microencapsulation of anthocyanins from a blueberry extract. The coupling of wall materials also led to considerably enhanced EE and stability. The lowest EE of 96.80% was recorded for the mixture of maltodextrin/hi-maize starch/inulin, while the superior EE, 98.83%, was observed for maltodextrin/hi-maize starch/inulin/ gum Arabic. The latter sample also had the lowest anthocyanin loss (4.45%, 5.82%, and 5.94% at freezing temperature, during refrigeration, and at RT, respectively) and the most prolonged half-life (913.41 days at freezing temperature, 693.32 days during refrigeration, and 679.81 days at RT) throughout the storage period. According to [PERSON] et al. [40], 30% maltodextrin as a carrier agent had the best performance regarding anthocyanin retention compared to 25% Capsu1(tm + 5% maltodextrin and 25% Arabic gum + 5% maltodextrin. [PERSON] et al. [41] also used maltodextrin, gum Arabic, and whey proteins for the microencapsulation of blueberry, jussara, and jabuticaba anthocyanins. It was observed that the individual wall materials had EEs above 90%, with the highest belonging to maltodextrin, followed by whey protein concentrate and gum Arabic [41]. [PERSON] and [PERSON] [42] also reported the greatest EE of 94% for the lowest quantity of \(\beta\)-glucan (0.5%) as a carrier material for elderberry anthocyanins. In contrast, this figure for the combination of maltodextrin and Arabic gum was 80%. Hence, the choice of wall material for spray drying microencapsulation has an impact on the EE because of the disparity between carriers' properties in terms of viscosity, solid content, film-forming capacity, and cost. Regardless of the benefits presented by this method, the high temperatures needed in the process can degrade the anthocyanins.