Encapsulation of Rosmarinus officinalis essential oil in β‐cyclodextrins

The aim of this study was to investigate the encapsulation process of R. officinalis (rosemary) essential oil (REO) in beta cyclodextrin (β-CD), by co-precipitation, using response surface methodology (RSM), specifically the face-centered central composite design (FCCCD). Solid-to-solid (β-CD/REO) and liquid-to-liquid (ethanol/water) ratios were selected as independent variables and their influence on the dependent variables was assessed. The recovered powder was characterized by different techniques, such as scanning electron microscope (SEM), Fourier Transform-Infrared Spectroscopy (FTIR) and X-Ray Diffractometry (XRD). Moreover, the release of REO from the β-CD complexes was investigated at different temperatures and pH values. The responses were affected by the concentration of ethanol in the reaction mixture and the amount of REO used. The optimal responses set by the RSM model (p-value < 0.05) were obtained for the optimal parameters ranging from 1.25:1 to 1.7:1 and 16.25:83.75 to 17.5:82.5 for ethanol/water and β-CD/REO ratios, respectively. The size of the inclusion complexes from the experimental condition 1:1 ethanol/water and 10:90 β-CD/REO ratios was the highest, with a value of 2.735 ± 0.192 µm. Furthermore, the FTIR spectra of inclusion complexes revealed a band downshift relative to the spectrum of β-CD, attributable to hydrogen bonding between REO components and β-CD, as well as a new band at 1,747 cm−1, revealing the presence of oil components, while the XRD patterns of β-CD recorded before and after the inclusion process indicate a change from a cage-type packing to a channel-type packing of cyclodextrin, which, in turn, indicates a successful inclusion process. Practical applications The encapsulation of EOs into cyclodextrins can enhance their biological properties, which include antioxidant, antimicrobial, anticarcinogenic, anti-inflammatory, and antidepressant activities. Nevertheless, a careful evaluation of the encapsulation conditions should be carried out in order to ensure the highest encapsulation yield without quality loss. In this way, pH and temperature, among other conditions, must be considered for evaluation since food or other matrices may present diverse pH values and be subjected to different temperatures. The present work may contribute to the use of rosemary EOs, with antioxidant and antimicrobial properties, in food and cosmetic industries, avoiding the sometimes-unpleasant flavor and aroma characteristics.