# Microencapsulation of Natural Food Antimicrobials: Methods and Applications
## 2 Encapsulation Methods
### Molecular Inclusion  
Cyclodexttrins (CD), known as cyclic oligosaccharides, are derived from starch through an enzymatic transformation catalyzed by cyclodextrin glycosyltransferase. They are composed of six, seven and eight \(\alpha\) (1-4) bonded glucopyranose units, known as \(\alpha\) (alpha), \(\beta\) (beta) and \(\gamma\) (gamma) cyclodext, respectively [36]. Cyclodextrin molecules, nontoxic carbohydrates \"generally recognized as safe\" (GRAS), can be used in the food industry for various purposes, including encapsulation of flavors and EOs as additives and protectants. These starch derivatives exhibit toroidal and truncated hollow cone structures with hydrophobic cavities and hydrophilic external surfaces. Thus, amphiphilic cyclodext (host) are capable of establishing inclusion complexes with hydrophobic compounds (guest) such as EOs to increase their solubility, to mask unpleasant flavor and tastes, to preserve guest molecules from degradation during processing and storage and also to convert liquid substances into solid forms [37]. The release of water molecules from the inner CD cavity is defined as the pivotal driving force for the complex formation. Molecular encapsulation is a process that produces a non-covalent inclusion complex through releasing CD ring strain after which van der Waals forces and hydrogen bond interactions occur [36]. The encapsulated flavors, as well as EO, show improved chemical and thermal stability and unique release characteristics. The release of flavor compounds occurs in the presence of the proper substrate by displacing guests from the cavity and producing more stable CD complexes [38]. Different methods, such as kneading, co-precipitation, \begin{table}
\begin{tabular}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline
**Microencapsulation Method** & **Wall Material** & **Antimicrobial Agent** & **Encapsulation Efficiency** & **Main Results** & **References** \\ \hline \hline \multirow{3}{*}{Alginate microbeads} & Calcium–Alginate & Clove, thyme and cinnamon EOs & 90 to 94\% & \begin{tabular}{c} Encapsulation in \\ Ca-alginate microspheres \\ could effectively reduce the evaporation rate of EOs \\ \end{tabular} & [29] \\ \hline \multirow{3}{*}{Alginate microbeads} & Sodium & \multirow{3}{*}{Nisin} & \multirow{3}{*}{36.35\%} & The encapsulation efficiency of nisin under optimal conditions was 36.65\% & [30] \\  & & & & \\ \hline \multirow{3}{*}{Ionic gelation} & Sodium alginate & Propolis extract & 99.3\% & \begin{tabular}{c} Na-alginate encapsulation \\ increased the bioavailability \\ of propolis extract \\ \end{tabular} & [31] \\ \hline \hline \multirow{3}{*}{SAS} & PLGA and CaCO\({}_{3}\) & Lysozyme & \(\sim\)60\% & \begin{tabular}{c} The supercritical CO\({}_{2}\) \\ process offers optimal \\ conditions for protein \\ stability and integrity and \\ permitted the retention of \\ 90\% of the biological activity \\ of lysozyme \\ \end{tabular} & [32] \\ \hline \hline \multirow{3}{*}{Liposome} & PC, PC/PG & Nisin & \
\begin{tabular}{c} 89–91, 78–83 and \\ 72–78\% for PC/PG \\ 64, PC/PG 8:2 and \\ PC, respectively \\ \end{tabular} & Liposomes formulated with PC and PG appeared to be relatively stable to pasteurization protocols & [33] \\ \hline \multirow{3}{*}{Liposome and emulsification method} & \multirow{3}{*}{
\begin{tabular}{c} Lecithin–chol \\ Alginate, chitosan \\ or starch \\ \end{tabular} } & Plant herbs, spices and lysozyme are more active & [34] \\  & & lyzozyme & against different types of bacteria & \\ \hline \hline \multirow{3}{*}{Vibrating technology} & \multirow{3}{*}{alginate} & \multirow{3}{*}{Nisin} & \multirow{3}{*}{75\%} & Microcapsules efficiently protected nisin from protease activity and retarded nisin release & [35] \\ \cline{1-1} \cline{4-4}  & & & & \\ \hline \end{tabular}
\end{table} 
Table 1: Cont. spray drying and freeze drying, have been suggested for the inclusion of CD complexes based on the properties of both active host compounds and guest molecules [37].