正交實驗設計評估微波萃取工藝──以龍柏精油為例

Use of Orthogonal Experimental Design to Evaluate Microwave-Assisted Extraction: A Case Study on Dragon Juniper Essential Oil

龍柏是柏科(Cupressaceae) 圓柏屬(Juniperus) 之常綠小喬木，拉丁學名：Juniperus chinensis L. var. kaizuka Hort.，為園藝景觀培育品種，也是木雕藝術品重要原料之一。本研究以正交實驗設計法L4(23) 正交表評選微波萃取之最適化條件，運用於龍柏精油之萃取。以萃取時間、微波功率、乾式龍柏試材重量占比為控制變因，分別設定兩項水平進行研究，試驗結果顯示最適萃取條件是萃取時間設定41 分鐘、功率600 瓦、乾式龍柏試材重量占比40% 可獲得最佳精油萃取率，其值高達0.68% 之多。萃取之精油經氣相層析- 質譜分析儀分析其成分比例，顯示含量最為豐富的成分分別是α- 雪松醇(alpha-Cedrol) 占比37.116% ± 2.086%、α- 雪松烯(alpha-Cedrene) 占比16.077% ± 1.603%、反式- 羅漢柏烯(cis-Thujopsene) 占比5.414% ± 0.361%。本研究實驗發現微波萃取是既快速又優質，值得開發應用於龍柏精油萃取的方式。

"Juniperus chinensis L. var. kaizuka Hort. or dragon juniper, is a small evergreen arbor in the family Cupressaceae and genus Juniperus. Dragon juniper is mainly bred for horticultural or landscaping purposes and is as a crucial raw material for wood carving. This study adopted an orthogonal experimental design, in which an L4(23) orthogonal array was used to evaluate and determine the most suitable conditions for the microwave-assisted extraction (MAE) of essential oil from dragon juniper. Extraction time, microwave power, and dry specimen weight were used as the control variables to configure two parallel experiments. The experimental results revealed that the optimal extraction conditions involved an extraction time of 41 min, microwave power of 600 W, and dry specimen weight ratio of 40%, which yielded an essential oil extraction rate of 0.68%. Gas chromatography–mass spectrometry analysis was performed to determine the composition ratio of the extracted oil, in which α-cedrol constituted the highest ratio (37.116% ± 2.086%), followed by α-cedrene (16.077% ± 1.603%) and cis-thujopsene (5.414% ± 0.361%). This study verified that MAE considerably reduced the extraction time, requiring only 14% of the time necessary for steam distillation. In addition, the extraction rate was improved by 0.25%, and the α-cedrol content was increased by 2.4 times. MAE therefore constitutes a rapid and efficient method for extracting essential oil from dragon juniper and merits further research and development."