加工處理對牛蒡茶泡飲機能成分溶出之影響

牛蒡 (Arctium lappa L.) 是菊科牛蒡屬的肉質根蔬菜，含有豐富的綠原酸、咖啡酸、菊糖、β-胡蘿蔔素、精胺酸與抗氧化物質，具有降血脂與血糖、保肝、壯陽及改善腸胃道等機能性功效。牛蒡較常被製作成加工產品，如牛蒡茶、醃漬牛蒡、牛蒡脆片與牛蒡膠囊等，研究表明，牛蒡茶具有降血脂與抗氧化等功效。茶是世界三大飲品之一，但卻未見牛蒡茶被大力推廣飲用。因此，本研究欲利用非熱加工與熱加工探討何種加工方法可增加牛蒡中綠原酸的釋出，再以不同烘乾溫度與不同牛蒡尺寸探討機能性成分溶出的情形與抗氧化活性。牛蒡經過高壓與酵素滲透處理後與未處理相比，綠原酸的含量皆降低了50%，可能是由於非熱處理無法完全滅活牛蒡中的多酚氧化酶 (PPO) 與過氧化酶 (POD)。經過熱處理後，PPO與POD的活性可降至9%與15%，綠原酸的含量於處理3分鐘時相較於未處理增加20%，可見適當的熱處理可透過滅活PPO與POD且破壞牛蒡組織使綠原酸釋出，且以100℃浸泡市售牛蒡茶20分鐘可溶出最多的綠原酸。牛蒡切丁較切片可溶出較多的綠原酸，而將片狀烘乾的牛蒡切成丁狀則可增加溶出量，但磨粉後則會降低。進一步探討其餘成分的溶出情形，發現以40℃烘乾可保留較多的菊糖與精胺酸且有較高的DPPH自由基清除能力，而180℃下則是保留較多的酚類化合物，例如：咖啡酸、總酚與類黃酮，且有較高的ABTS自由基清除能力、還原力與亞鐵離子螯合力，不論何種乾燥溫度的牛蒡茶皆有媲美對照組 (維生素C或EDTA) 優秀的抗氧化能力。總結而言，以短時間熱處理可滅活牛蒡中的PPO與POD，相較於非熱加工更有優勢。若能以較適合的條件製作牛蒡茶，再以最適合的浸泡條件浸泡飲用可提升牛蒡的營養利用效率，其優秀的抗氧化活性使牛蒡茶成為保健養生的飲品，期望透過本研究達到推廣飲用牛蒡茶的效果。

關鍵字

牛蒡；牛蒡茶；熱處理；抗氧化；清除自由基；綠原酸

並列摘要

Burdock (Arctium lappa L.) is a fleshy root vegetable belonging to Arctium in the family of Asteraceae. It is rich in chlorogenic acid (CGA), caffeic acid (CA), inulin, β-carotene and L-arginine (L-Arg) and antioxidants. It is also known for being hypolipidemic, antidiabetics, hepatoprotective, aphrodisiac, and maintaining gastrointestinal health. Burdock is more commonly consumed as processing products, such as burdock tea, pickled burdock, burdock crisps, and burdock capsules. Studies have shown that burdock tea has hypolipidemic and antioxidative effects. Tea is one of the world's most popular beverages; however, burdock tea has not yet been promoted for drinking. This study aims to explore processing methods that increase the release of CGA in burdock by using non-thermal processing and thermal processing. We used different drying temperatures and cutting sizes to analyze the dissolution of functional ingredients and their antioxidant activities. The content of CGA after high pressure and enzyme penetration treatment reduced by 50% compared with the untreated control. This may be due to incomplete inactivation of polyphenol oxidase (PPO) and peroxidase (POD) during non-thermal processing. After heat treatment, the residual activities of PPO and POD in burdock reduced to 9% and 15%, respectively. The content of CGA after heat treatment for 3 min increased by 20% compared with the untreated control. The appropriate heat treatment released CGA by inactivating PPO and POD and destroying burdock tissue. Brewing commercial burdock tea at 100°C for 20 min dissolved most of the CGA. Dried burdock released more CGA diced than sliced. Chopping sliced burdock released more CGA, but grinding into powder reduced the dissolution of CGA. Then, we discussed the dissolution of the remaining ingredients. Drying burdock at low temperatures retained more inulin and L-Arginine, whereas at high temperatures it retained more phenolic compounds (CA), the total phenolic and flavonoid content. The low drying temperature increased 1, 1-Diphenyl-2-Picrylhydrazyl (DPPH) free radical scavenging ability of the burdock tea, while at high temperatures, it showed higher 2, 2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radical scavenging ability, reducing power, and ferrous ion chelating power. Regardless of the drying temperature, the burdock tea has an excellent antioxidant efficiency, which is comparable to that of the positive control (vitamin C or Ethylenediaminetetraacetic acid (EDTA)). Drinking burdock tea may be better than eating some fruits and vegetables. In summary, short durations of heat treatment can inactivate PPO and POD in burdock, and therefore this method is more advantageous than non-thermal processing. If the burdock tea is prepared under conditions, such as dried in dices, dried at high temperature to retain the phenolic compounds, dried at low temperature to retain the functional ingredients, and then brewed in the most suitable conditions for drinking, the nutrition of burdock could be absorbed more efficiently. Its excellent antioxidant activity makes burdock tea a health drink. This study shows the potential benefits of drinking burdock tea.