Encapsulation and characterization of some essential oils and active substances by sol-gel method

Essential oils are being used in the food, medicine, cosmetic and household cleaners industries because of their odour, flavour and biological effects. In the recent years, the usage of essential oils by people is increasing with the increasing interest to alternative medicine. Within the scope of this study, essential oils were obtained by the hydrodistillation method from the Origanum minutiflorum (origanum), Eugenia caryophyllata (clove), Eucalyptus camaldulensis (eucalyptus) and Cymbopogon citratus (lemon balm) plants. The active substances carvacrol, eugenol and 1,8-cineole were isolated from the obtained essential oils. Isolated active substances were characterized by Gas Chromatography/Mass Spectrometry (GC-MS) and Gas Chromatography-Flame Ionization Detector (GC-FID), Nuclear Magnetic Resonance Spectroscopy (NMR) and Fourier Transform Infrared Spectroscopy (FT-IR). Isolated active substances, standard active substances and essential oils were encapsulated with sol-gel and freeze drying methods. The structure and thermal characteristics of encapsulated essential oils and active substances which were in powdery form were characterized with Scanning Electron Microscope (SEM), FT-IR, Surface Area and Porosity Analysis (BET), Thermogravimetric Analysis (TGA) and 29Si-NMR Analysis. Chemical extraction and chemical derivatization methods were practised for isolation of the active substances. Essential oils, isolated active substances and standard active substances were dispersed by using Tween 20 surfactant in the sol-gel encapsulation process. Colloidal silica (Ludox 40) were used as a starting material for the sol-gel reaction. Tween 20 and colloidal silica amounts were optimized individually according to each material which will be encapsulated. Arabic gum and arabic gum:gelatine:sucrose (1:1:1) processes were realized with the freeze drying method. As a result of the study, carvacrol was isolated from Origanum minutiflorum oil with a purity of 99.37 %, eugenol was isolated from Eugenia caryophyllata oil with a purity of 99.86 %, 1,8-cineole was isolated from Eucalyptus camaldulensis oil with a purity of 97.78 %. In the sol-gel encapsulation, capsule diameters varied between 7.85 nm and 21.50 nm, encapsulation efficiency varied between 5.22 % and 77.76 %. In the freeze drying process pore diameters varied between 12.73 nm and 30.29 nm, encapsulation efficiency varied between 9.40 % and 85.72 % in the arabic gum implementation. In the mixture implementation pore diameters varied between 2.99 nm and 55.66 nm, encapsulation efficiency varied between 16.27 % and 98.66 %.