|摘要: ||薄荷(Mentha spp.)為唇形花科(Labiatae)薄荷屬多年生草本宿根植物，為一常見且廣泛運用之特用作物。本試驗以中國薄荷(Mentha arvensis ssp. Haplocalyx, China mint)、茱莉亞甜薄荷(Mentha × rotundifolia ‘Julia’s Sweet Citrus’, Julia’s sweet mint)、越南薄荷(Mentha × gracilis ‘Vietnam’, Vietnam mint)和土薄荷(Mentha Canadensis, Native mint)為材料，先探討三期作中四個物種薄荷地上部鮮乾重產量、精油產量及揮發油中薄荷醇與薄荷酮濃度之差異，再以水蒸餾法及不同條件之微波輔助水蒸餾法萃取薄荷精油，比較各方法間薄荷精油萃取量及精油中薄荷醇與薄荷酮之濃度差異；並利用不同薄荷醇濃度之精油進行薄荷結晶試驗，欲找出較佳之結晶條件。四個物種薄荷中以中國薄荷的周年產量最高，茱莉亞甜薄荷次之，越南薄荷最低；周年總精油產量以茱莉亞甜薄荷最高，其餘三者間無顯著差異；薄荷醇濃度以茱莉亞甜薄荷最高，其次為越南薄荷和土薄荷，中國薄荷最低；薄荷酮濃度以土薄荷和越南薄荷較高，中國薄荷最低；此外在第二次宿根栽培中茱莉亞甜薄荷地上部鮮乾重產量和精油產量皆最高。在不同萃取方法中以水蒸餾法之精油萃取量最高，其餘五種微波萃取方法間除微波萃取15 mins最低外，彼此間無顯著差異，而精油中薄荷醇濃度則除第二次宿根栽培外，皆以水蒸餾法萃取之精油最低；分析精油中各組成分的比例發現以水蒸餾法萃取之精油中薄荷醇所佔面積比例最低。在結晶試驗方面以56%精油在4℃下即可獲得薄荷結晶，且配合更換精油與梯度降溫的方式可以增加晶體直徑，提升薄荷結晶的品質。|
Mint (Mentha spp.), which is belong to Labiatae, is a perennial aromatic herbs, it’s not only the most important raw material for essential oils on the world but also have many medical uses. In the present study, Mentha arvensis ssp. Haplocalyx (China mint), Mentha × rotundifolia ‘Julia’s Sweet Citrus’ (Julia’s sweet mint), Mentha × gracilis ‘Vietnam’ (Vietnam mint) and Mentha Canadensis (Native mint) were used to investigate the yield of shoot fresh weight, shoot dry weight, volatile oil content, menthol and menthone concentrations during annual cropping seasons, also compare the extract efficiency between conventional hydrodistillation and different condition of microwave-assisted hydrodistillation, and try to find a better way to prepare the menthol crystals in advance. The results showed that shoot weight, volatile oil content, menthol and menthone concentration, and volatile oil yield varied considerably among the selected species, cropping seasons, and extract methods. China mint grew better and produced more above-ground shoots than the others, but Julia’s sweet mint produced more volatile oil yield, particularly menthol in its shoot than Vietnam mint, Native mint and China mint. Generally, the yield of shoot weight, volatile oil production in second ratoon season were highest than the other cropping seasons. Extract efficiency indicated that hydrodistillation extracted more volatile oil content than microwave-assisted extraction, but less menthol concentration. In the crystallization trial , we can obtain the menthol crystal in 56% volatile oil under 4℃. Gradient cooling temperature and oil substitution during chilling phase provided a significant effects on the quality of menthol crystal.