# Microencapsulation of Natural Food Antimicrobials: Methods and Applications
## 3 Microencapsulation of Natural Food Antimicrobials
### Essential Oils
Pure coriander EO, as a biologically active agent, is made up of different amounts of various complex components, including oxygenated monoterpenes such as geraniol, linalool, menthol, citronello; and monoterpene hydrocarbons such as thymol, carvacrol, guaiaicol, limonene and sesquiterpens. High inclusion efficiency of coriander EO (122 mg g\({}^{-1}\)) was achieved with the EO/\(\beta\)-CD mixture ratio of 15:85. The encapsulated EO showed high antimicrobial activity against _Aspergillus niger_ MIUG M5 and _Penicillium glaucum_ MIUG M9 strains with an inhibition growth zone of 3.1 and 3.0 mm, being lower than the 7.5 and 6.5 mm obtained for antifungal activity of free oil, respectively. Coriander EO/\(\beta\)-CD complexes could retain up to 41-46% of antimicrobial activity of the free EO [87]. Antimicrobial properties of encapsulated coriander (_Cariandrum sativum_) and parsley (_Petroselinum crispum_) EOs in \(\beta\)-CD were investigated separately against Gram-positive and Gram-negative bacteria using the colorimetric broth microdilution method. The MIC values of encapsulated EOs against _Listeria innocua_, _Achromobacter denitrificans_, _Shewanella putrefaciens_, _Enterobacter annigenus_ and _Pseudomonas fragi_ were close to each other and ranged between 10 and 20 mg/mL. The higher resistance of all tested bacteria to encapsulated EOs in \(\beta\)-CD compared to free nisin (MIC: 0.625-2.5 mg/mL) could be attributed to enhanced microbial growth supplied by the carbon source of \(\beta\)-CD as a starch-derived polymer [88]. However, it has been reported that encapsulated coriander oil in chitosan does not have antibacterial activity. Chitosan capsules containing coriander oil showed lower antimicrobial activity than pure chitosan capsules. According to the authors, covering the surface of capsules with EOs with no activity reduced the antimicrobial activity of chitosan [83]. Encapsulated EG in \(\beta\)-CD exhibited significant antibacterial activity after application of a thermal process at a temperature of 80 \({}^{\circ}\)C for 2 h. EG/\(\beta\)-CD complexes had lower MIC values against _E. coli_ and _Staphylococcus aureus_ than pure EG molecules due to enhanced EG solubility in an aqueous medium relating to the hydrophilic properties of cyclodex-trins. Moreover, the antibacterial activity of microcapsules containing a high amount of EG (17.08 mmol/L) was higher than other microcapsules with lower agent concentrations (9.68 and 10.90 mmol/L) and pure EG molecules [11]. The antibacterial activity of solid-state EG/\(\beta\)-CD inclusion complexes has been evaluated through an agar cup-plate method with three different concentrations, including 10.0, 5.0, and 2.5 mg/mL (saturated solution of EG/\(\beta\)-CD powder at room temperature), against _E. coli_, _Salmonella paratyphi B_ and _S. aureus_. EG/\(\beta\)-CD complexes showed a clear inhibitory effect only against _E. coli_ with the best result being obtained for the 10 mg/mL solution, indicating the selective antimicrobial activity of prepared complexes against bacterial strains. Free EG did not have any inhibitory effect against studied microorganisms due to two reasons: (i) the slow diffusion of free EG through agar due to the very low solubility level in water and (ii) the high volatility. Cinnamon bark oleoresin (CO) is used in cakes and confectionary as a flavoring agent from bark essential oil. Oleoresin applications in food products is, however, limited due to diverse drawbacks, including being more concentrated than essential oils and degradation by light, heat and oxygen exposure, which can be solved by the encapsulation process [85; 89]. Different ratios of palm hard fat (PH): palm oil (PO) (100:0, 80:20, 60:40) were tested as carriers for the encapsulation of CO (1-2%) by a spray-chilling method.