Study On Extraction Of Essential Oils From Kaempferia Galangal L. By Ultrasound-enhanced Subcritical Water

Regarding as a brand-new technology, subcritical water extraction (SWE), had attracted world-wide attention due to its own considerable merits such as a shorter extraction time with higher quality and productivities, low energy comsuption as well as environmentally friendly. It is recognized that the SWE is a revolutionary technology with an extensive future and huge potential. In this dissertation, ultrasound was used to enhance the process of SWE, aiming at imporving the extraction rate. More specifically, ultrasound-enhanced subcritical water extraction (USWE) of essential oils from Kaempferia galangal L. were studied, aiming at mordenizing the extraction process of Kaempferia galangal L. oils and reforming the backward traditional technique, thereby offering theoretical references for the industrialized Kaempferia galangal L. oils.Based on the apparatus of USWE which was successfully designed and developed by our lab, and taking the extraction yield of ethyl p-methoxy cinnamate which accouts for the effective component of Kaempferia galanga L. as the target index, the SWE, enzymatic subcritical water extraction (ESWE) and USWE of essential oils from Kaempferia galangal L. were studied. The extraction efficiencies of ultrasound power density and frequency, mode of ultrasound wave irradiation extraction, the dosage of the liquefying enzyme, extraction temperature, time and pressure wer explored and optimal extraction conditions were investigated. Moreover, the comparison among USWE, ESWE, SWE and steam distillation (SD) in terms of extraction condition, the compositions of the essential oils as well as biological efficacy was also studied. Finally, the mathematic model of SWE and USWE of essential oils from Kaempferia galangal L.was built, more than that, the degree of fitting between prediction results and experimental results was checked.The experimental results of SWE showed that extraction temperature, time and material mass were major factors affecting the extraction yield. The optimal extraction condition was material mass 100 g, 40~60 meshes, extraction temperature of 120°C, time of 30min, and pressure of 10MPa. At this optimum condition the extraction yield of ethyl p-methoxy cinnamate was 24.17mg?g-1.The experimental results of ESWE showed that extraction temperature, material mass, the dosage of the liquefying enzyme and extraction time were major factors affecting the extraction yield. The optimal extraction condition was material mass 100 g, 40~60 meshes, the dosage of the liquefying enzyme is 0.3%, extraction temperature of 120°C, time of 20min, and pressure of 8MPa. At this optimum condition the extraction yield of ethyl p-methoxy cinnamate was 25.28mg?g-1.The experimental results of USWE showed that extraction temperature, ultrasound power density, material mass and extraction time were major factors affecting the extraction yield. The optimal extraction condition was material mass 100 g, 40~60 meshes, extraction temperature of 120°C, time of 20min, pressure of 10MPa, ultrasound power density of 250W/L, ultrasound frequency of 20kHz, and ultrasound action start time of 0min. At this optimum condition the extraction yield of ethyl p-methoxy cinnamate was 25.80mg?g-1.The comparison among USWE, ESWE, SWE and SD showed that the ultrasound introduction accounts for a shorter time with higher productivity, that is, the shortest extraction time and the yield of ethyl p-methoxy cinnamate was also the highest, increased about 2.06%, 6.74% and 60.85% compared to the ESWE, SWE and SD, respectively. According to the concerntration of ethyl p-methoxy cinnamate of the Kaempferia galangal L. oils, the USWE peaking at 10.53mg?g-1 which represented the best quality. GC-MS was used to determine the quality and the structure of effective components. The results showed that higher temperature and ultrasound did not change the effective component of essential oils, but the concentrations differed. The results from anti-oxidation activity of Kaempferia galangal L. oils showed that all Kaempferia galangal L. oils from four different extraction methods had good anti-oxidation activity, and the essential oils from USWE showed the best activities.Based on transfer theory and principle of mass balance, the kinetic models of subcritical water extraction and ultrasound-enhanced subcritical water extraction were built, that is, E = E∞(1 ? e?kt). The prediction results of the model fit the experimental results well, and both of them can actually present the practical extraction process. Furthermore, the values of E∞and k showed that ultrasound could enhance the extraction process of SWE.