# Microencapsulation of Anthocyanins--Critical Review of Techniques and Wall Materials
## 2 Microencapsulation Techniques  
### Physical Methods  
#### 2.1.1 Spray Drying  
Spray drying (SD) is one of the oldest and industrially common microencapsulation methods, and about 80 to 90% of anthocyanins have successfully been encapsulated via this technique [22]. SD consists of three key stages [23]:  
1. Atomization of the fluid feed in the form of suspension, solution, or emulsion through a high-pressure nozzle into a drying chamber. 2. Direct contact between the sprayed droplets and the heating medium typically occurs at 150-220 \({}^{\circ}\)C, leading to evaporation of the solvent. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Method** & **Benefits** & **Drawbacks** & **Variable Parameters** & **Reference** \\ \hline Inclusion complex & \begin{tabular}{c} Preserves anthocyanins \\ from polymerization, oxidation, and degradation reactions. \\ Providides thermal \\ stability and controlled \\ release properties. \\ \end{tabular} & \begin{tabular}{c} Low solubility of \\ \(\beta\)-CD in water leads \\ to precipitation or a \\ viscous solution at \\ high concentrations. \\ \end{tabular} & \begin{tabular}{c} Inclusion temperature, \\ solvent, structure, and \\ polarity of the guest \\ molecules and host cavity. \\ \end{tabular} & [10] \\ Inclusion complex & \begin{tabular}{c} Ecofriendly and no \\ surfactants are needed. \\ Higher coalescence \\ stability, strong \\ protection, storage \\ stability, and tailored \\ release. \\ \end{tabular} & Industrialization. & \begin{tabular}{c} Particle wettability. The oil \\ phase and oil-to-aqueous \\ phase ratio. Particle \\ concentration and surface \\ coverage. Particle charge, \\ salt concentration, and pH. \\ Emulsion preparation \\ method, and temperature. \\ \end{tabular} & [18] \\ Pickering emulsions & \begin{tabular}{c} Increased adsorption \\ and bioavailability. \\ Nontoxic and \\ nonimmunogenic. \\ \end{tabular} & \begin{tabular}{c} Low encapsulation \\ efficiency. Lipid \\ oxidation, poor \\ physicochemical \\ stability, and wide \\ particle size \\ distribution. \\ Postprocess step is \\ required. \\ \end{tabular} & & \begin{tabular}{c} Source and concentration \\ of phospholipid. Buffer \\ pH. \\ \end{tabular} & [6, 10] \\ Liposome system & \begin{tabular}{c} Low cost and does not \\ require advanced \\ equipment, high \\ temperatures, and \\ organic solvents. \\ \end{tabular} & \begin{tabular}{c} Rapid release when \\ hydrophilic or low- \\ molecular-weight \\ materials are \\ encapsulated. \\ \end{tabular} & \begin{tabular}{c} Concentration of the \\ crosslinking polyelectrolyte \\ and wall material solution. \\ Reaction and stirring time. \\ Core-to-wall material ratio. \\ \end{tabular} & [19, 20] \\ \hline Loic gelation & \begin{tabular}{c} High loading capacity, \\ low temperature \\ operating requirements, \\ reduced evaporation \\ losses of volatile \\ compounds, and \\ thermal degradation. \\ Tailored release of \\ active compounds. \\ \end{tabular} & \
\begin{tabular}{c} Produced particles \\ are very sensitive to \\ pH and ionic strength. \\ Agglomeration of \\ particles and particle \\ size control. \\ Complexity of the \\ method. \\ \end{tabular} &
\begin{tabular}{c} Concerning parameters: \\ emulsion preparation \\ method, \\ temperature of the \\ medium, pH and ionic \\ strength, crosslinking and \\ drying methods. \\ Material properties: \\ chemical composition, \\ concentration, charge \\ weights of polymers, and \\ weight ratio. \\ \end{tabular} & [21] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._Separation and recovery of the powdered product from the air using a filter or cyclone. This technique is rapid, versatile, cost-effective, easy to scale up, and generates high anthocyanin retention and relatively good storage stability. On the other hand, the atomization process produces particles with a high surface-to-volume ratio, which provokes thermal exposure and, consequently, degradation of anthocyanins and a reduction in the antioxidant activity of the microcapsules.