| Summary: | 碩士 === 國立臺灣大學 === 食品科技研究所 === 102 === 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＜0.05）powerful inhibition of lipid oxidation, but after fermentation by L. plantarum BCRC 11697 for 24 hours, red beet juice showed best inhibition of lipid oxidation. Finally, in this research, results showed that the antioxidative activity of red beet juice can be improved by lactic acid bacteria fermentation, furthermore, red beet juice fermented by L. plantarum BCRC 11697 for 24 to 36 hours showed best antioxidative activity and stability.
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