| Popis: |
To enhance the essential oils yields for hydrodistillation of bay laurel and sage, the impact of ultrasonic and enzymatic pretreatment (under optimized xylanase activity) was investigated. Response surface methodology (RSM) was used to optimize the reaction conditions of pH, temperature, and reaction time to obtain maximum xylanase activity. The impact of optimized conditions during enzymatic pretreatment induced variations in the essential oil yields. After the pretreatments, bay laurel and sage essential oils were isolated using Clavenger type apparatus and their yields were measured and compared with the essential oils obtained from non-treated plant materials (no pretreatment control). In order to determine the impact of pretreatments on the chemical composition, isolated essential oils were analyzed by gas chromatography and mass spectrometry (GC-MS), and afterward, the correlations were tested using Spearman’s test. The main constitutes of the sage essential oils are oxygenated monoterpens (α- and β-thujone, 1, 8-cineole and camphor). 1, 8-cineole is the major component of bay laurel essential oils, followed by α-terpinyl acetate, and several monoterpene hydrocarbons and phenylpropane derivates with dominant components eugenol and methyleugenol. Several chemical compounds (mostly oxygenated monoterpenes) of bay laurel and sage essential oils were detected in greater quantity after the ultrasonic and enzymatic pretreatments in comparison to untreated plant material.However, the results showed that despite optimization, the activity of xylanase did not significantly affect the quantity and quality of bay laurel and sage essential oils. The main advantage of ultrasonic extraction is shortening of the pretreatment time and only 10 minutes of ultrasonic pretreatment before the enzymatic pretreatment caused 50 % enhancement of sage and 40 % of bay laurel essential oil yields. Due to their chemical composition (oxygenated monoterpenes, monoterpene and sesquiterpene hydrocarbons), the essential oils obtained by the ultrasonic and enzymatic pretreatment prior hydrodistillation possess potential in the food industry applications. |
