Improvement of antioxdative and enzymatic activities of red beet juice by lactic acid bacteria fermentation

紅甜菜（Beta vulgaris）營養豐富，現今為甘蔗以外重要的製糖原料之一，並且廣泛應用於西方國家之餐點上，而當中所富含之甜菜色素除了作為食品加工使用之天然色素外，更具有良好之抗氧化能力。本研究經篩選後選擇以具有高β-glucosidase及superoxide dismutase活性之Lactobacillus plantarum BCRC 11697及Bifidobacterium bifidium BCRC 14615進行紅甜菜汁之發酵，第一部分首先探討最適化之發酵條件，最終將紅甜菜汁調整至6°Brix並添加2% tryptone、1% yeast extract，於30℃發酵36小時後，可使L. plantarum BCRC 11697表現出最高之β-glucosidase活性達17.29±0.48 mU/mL，以及superoxide dismutase活性達22.45±0.67 U/mL。而第二部分探討紅甜菜汁經L. plantarum BCRC 11697及B. bifidium BCRC 14615發酵後，其抗氧化能力之變化情形，結果顯示紅甜菜汁之DPPH自由基清除能力及總抗氧化能力經兩者發酵12小時後皆有顯著性提升（p<0.05），而還原力則於發酵至48小時期間皆無顯著性變化；ROS超氧陰離子清除能力則於發酵24小時後具顯著性提升（p<0.05），其中以L. plantarum BCRC 11697發酵至36小時可達最高之清除率；最後測定抑制脂質過氧化能力之部分，顯示以B. bifidium BCRC 14615發酵12小時即有顯著性提升（p<0.05），而以L. plantarum BCRC 11697發酵24小時則可達最佳抑制脂質過氧化能力並維持至48小時。綜合本研究之結果，顯示紅甜菜汁經乳酸菌發酵後可確實提升其抗氧化能力，其中以L. plantarum BCRC 11697發酵24至36小時具有最佳效果，同 時具有較佳之穩定性。Beetroot（Beta vulgaris）is vegetable with highly renewable and cheap source of nutrients, that widely consumed in traditional western cooking. It’s an important raw material for sugar industry except for sugar cane. Furthermore, beetroot is abundant in red pigment, betalains, that not only used in food processing but also are excellent antioxidants. In this research, Lactobacillus plantarum BCRC 11697 and Bifidobacterium bifidium BCRC 14615 were selected for their high β-glucosidase and superoxide dismutase activity, and used as starters to ferment red beet juice. In first part of study, the optimal conditions for fermentation were investigated. Results showed that using 6°Brix red beet juice with 2% tryptone and 1% yeast extract, followed by fermentation at 30℃ for 36 hours, L. plantarum BCRC 11697 can exhibit highest β-glucosidase activity for 17.29±0.48 mU/mL and superoxide dismutase activity for 22.45±0.67 U/mL. In the second part of study, the antioxidative activity of red beet juice fermented by L. plantarum BCRC 11697 and B. bifidium BCRC 14615 were investigated. Results showed that DPPH scavenging ability and trolox equivalent of antioxidant capacity of red beet juice was significantly increasing（p<0.05）after fermentation by both lactic acid bacteria for 12 hours. But reducing power of red beet juice showed no significantly changes during fermentation up to 48 hours. The ROS scavenging ability of red beet juice were significantly increasing（p<0.05） after fermentation by both lactic acid bacteria for 24 hours, and further showed highest ROS scavenging ability after fermentation by L. plantarum BCRC 11697 for 36 hours. In the last test, antioxidant power against lipid oxidation, red beet juice after fermentation by B. bifidium BCRC 14615 for 12 hours showed significantly（p