Extraction Process Optimization, Composition Analysis and Sensory Evaluation of Volatile Oil from Thai Basil (Ocimum basilicum var. thyrsiflora)
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Abstract:
In this study, the SO3 micro-thermal explosion (STEX) pretreatment-assisted extraction process for the volatile oil from Thai basil (Ocimum basilicum var. thyrsiflora) was investigated. The chemical composition and aroma profile of the obtained volatile oil were also analyzed. The results showed that shade-drying and steam distillation (SD) were the best drying method and extraction method. The optimum conditions of STEX were: SO3 to dry matter mass ratio, 1:3; pretreatment temperature, 50 °C; pretreatment time, 30 min. The yield of volatile oil under such conditions was 0.56%, which was 46.41% and 90.48% higher than those of SD and water distillation (WD), respectively. The yield of volatile oil could be further increased to 0.60% in the scale-up validation experiment. Scanning electron microscopic examinations revealed that the microstructure of the STEX-pretreated Thai basil biomass was altered significantly, with severe surface wrinkling and significant stomatal expansion. The results of elemental and IR analyses revealed that the STEX pretreatment increased significantly the sulfur content in the Thai basil biomass without influencing the composition of chemical functional groups. GC-MS analysis revealed that methyl chavicol and methyl eugenol were the main components of the three volatile oils obtained from the basil biomass subjected to WD, SD and STEX-SD, among which, the volatile oil obtained by STEX-SD had the highest number of identified compounds (31 species). The sensory evaluation showed that fennel- and lemon-like notes were the main aromas of the three essential oils, with the aroma of the essential oil obtained by STEX-SD being more obvious. STEX can be used as an efficient pretreatment method to improve the yield and aroma quality of the volatile oils from aromatic plants such as basil.
