# Advances in the Application of Microcapsules as Carriers of Functional Compounds for Food Products
## 2 Methods for the Production of Microcapsules Loaded with Bioactive Compounds  
Several methods for the encapsulation of bioactive compounds have been studied, such as spray drying, coacervation, freeze drying, electrospraying, ionic gelation, and fluidized bed coating [30]. Table 1 shows an overview of the encapsulation systems referred recently in the literature, indicating the methods, the wall materials, and the bioactive compounds used. \begin{table}
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**Wall Material** & **Core Material** & \begin{tabular}{c} **Core Material** \\ **Source** \\ \end{tabular} & \begin{tabular}{c} **Main Properties/Applications** \\ **Studied** \\ \end{tabular} & **Refs.** \\ \hline \multicolumn{5}{c}{**Spray Drying**} \\ \hline Arabic gum & & & & \\ Gelatin & Anthocyanins & Barberry extract & Stabilization of active ingredient & [31] \\ Maltodextrin & & & & \\ Arabic gum & Anthocyanins & & Stabilization of active ingredient & \\ Maltodextrin & Carotenoids & Tamarillo & Storage stability & [32] \\ Arabic gum & & & & \\ Maltodextrin & Carotenoids & Carrot & Stabilization of active ingredient & [33] \\ Whey protein & & & & \\ Arabic gum & Carotenoids & Gac oil & \begin{tabular}{c} Storage stability \\ Incorporation in food matrix \\ \end{tabular} & [34] \\ Whey protein & & & Mango & Stabilization of active ingredient & \\ Maltodextrin & Carotenoids & Banana & Storage stability & [16] \\ Maltodextrin & & & & \\ Sodium caseinate & Carotenoids & Red palm oil & Stabilization of active ingredient & [17] \\  & & & Stabilization of active ingredient & \\ Arabic gum & Carotenoids & Tomato oleoresin & \begin{tabular}{c} Storage stability \\ Controlled release of bioactives \\ from microcapsules \\ \end{tabular} & [19] \\ Soy protein & & & & \\ Arabic gum & Carotenoids & \(\beta\)-carotene & Stabilization of active ingredient & [35] \\ Alginate & & & & \\ Chitosan & Essential oil & Coriander & \
\begin{tabular}{c} Controlled release of bioactives \\ from microcapsules \\ \end{tabular} & [23] \\ Inulin & Essential oil & Oregon &
\begin{tabular}{c} Controlled release of bioactives \\ from microcapsules \\ \end{tabular} & [36] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Encapsulation systems of bioactive compounds for food applications. Figure 2: Summary of topics addressed in this paper. \begin{table}
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Spray drying is one of the oldest techniques used for the production of microcaparticles, in which dehydrated products in the form of fine powders are obtained. Nowadays, this technique is widely used in the food industry due to its low production costs, simplicity, ease of scaling up, and ability to produce microparticles with good properties for several uses. Moreover, water removal by spray drying ensures the microbiological quality and facilitates the transport, dosing, and storage of the obtained products [59; 60]. The main drawback of the spray drying technology is the type of wall materials that can be used: as most formulations used by the food industry in this process are aqueous-based, the wall material used must have a good water solubility and simultaneously impart a suitable viscosity in order to enable the drying process [2; 61]. The microencapsulation process by spray-drying is comprised of the following steps: feed preparation (may be a solution, a suspension, or emulsion, containing the wall and core materials), atomization of the feed in small droplets, rapid drying of liquid droplets in contact with a stream of hot gas (e.g., air) resulting in the instantaneous formation of the microparticles in the form of powder, and finally powder recovery. The temperature of the drying inlet air used is usually between 110 and 220 \({}^{\circ}\)C, and the exposure time of the feed solution at these high temperatures is only a few milliseconds.