利用乳酸菌發酵提升臺灣藜的抗氧化能力

Abstract

臺灣藜 (Chenopodium formosanum Koidz.)，又名“紅藜”、“紅寶石”及“Djulis”，屬於臺灣原生種的植物，栽種於屏東、臺東與花蓮等地區 (臺東縣農會、信豐農場) 。臺灣藜是一種含有豐富營養素，維生素和礦物質的穀物，並具有特殊的營養價值，如抗氧化能力等。本研究的目的為透過液態發酵提升臺灣藜當中的抗氧化能力，製作出臺灣藜乳酸飲品。本研究中，臺灣藜會分別接種不同常用於發酵乳製品之益生菌進行發酵，並篩選出能夠產生最高抗氧化能力的益生菌，並透過反應曲面法優化發酵條件，最適化提升抗氧化能力，最後再針對各營養成分及活性成分進行分析。實驗結果顯示，利用DPPH自由基清除能力作臺灣藜的預處理及發酵時間的選擇，選擇90oC預處理10分鐘和24小時的發酵時間。後續在此條件下，以十株不同的乳酸菌進行發酵，並透過DPPH、ABTS+自由基清除能力和酚類化合物的含量作篩選條件，選出具有最好抗氧化能力的菌株Lactobacillus plantarum BCRC 11697，此菌株於DPPH及ABTS+自由基清除能力的結果均有顯著提升，DPPH從72.6%上升至93.2%；ABTS+從64.2%上升至76.9%。接著使用反應曲面法 (Response surface methodology) 針對發酵條件進行優化，以提高抗氧化能力。所選擇的發酵優化條件為初始pH值、轉速及發酵溫度。經最適化後，最佳的初始pH值、轉速及發酵溫度條件分別為pH 5.55、104 rpm和24.4oC。以RSM優化後的條件進行發酵，結果顯示，不論是DPPH和ABTS+自由基清除能力都有顯著的增加，發酵前分別為DPPH IC50 1.11 mg/ml；ABTS IC50 3.4 mg/ml，發酵後則為DPPH IC50 0.33 mg/ml；ABTS IC50 2.65 mg/ml，分別提升28%及26%。總酚含量含量顯著的提升了53% (p < 0.05)。以臺灣藜的蛋白質萃取液進行抗氧化能力的分析，亦發現不論是DPPH及ABTS都有顯著的提升 (p < 0.05)。

Chenopodium formosanum Koidz. also known as ‘Djulis’, is a plant native to Taiwan. Djulis has special nutritional value, because they are great sources of vitamins, minerals, complete protein and also bioactive compounds like antioxidants. Therefore, the purpose of this study is to enhance the antioxidant capacity of Djulis through the lactic acid fermentation to produce a nutraceutical food. In this study, different probiotics commonly used in fermented dairy products will inoculate in matrix for fermentation, and the probiotic with highest antioxidant activity will be select as the further experiment use, and then increase the antioxidant activity by using the response surface method. Result shows that, based on the ability of DPPH radical scavenging, the pretreatment of 90°C for 10 minutes and 24 hours of the fermentation time has been selected. The optimum probiotics - Lactobacillus plantarum BCRC 11697 was screened by phenolic compound, DPPH (from 72.6% to 93.2%) and ABTS (from 64.2% to 76.9%) free radical scavenging ability compared with different lactic acid bacteria. Then, response surface methodology used as to optimize the fermentation process to improve the antioxidant capacity. The optimal initial pH, rpm and fermentation temperature of improving antioxidant activity were pH 5.55, 104 rpm and 24.4°C. No matter phenolic compound, DPPH and ABTS free radical scavenging ability also showed significantly increase during fermentation process (p < 0.05), the IC50 of the DPPH and ABTS free radical scavenging ability were 0.25 and 2.65 mg/ml, DPPH and ABTS were increased 28% and 25%, respectively. Djulis protein also showed increasing of antioxidant activity.