| Summary: | 碩士 === 東海大學 === 畜產與生物科技學系 === 95 === Previuos investigation indicated that fermented dairy products and Sc. cerevisiae had the antioxidative ability. Therefore, this investigation was conducted to mix Sc. cerevisiae into yogurt, and expected to improve the antioxidative ability of yogurt. Firstly, six yogurts were made by mixing Streptococcus thermophilus (S1 and S2) and Lactobacillus bulgaricus (B1, B2 and B3), and the lowest antioxidative ability yogurt was selected as the improved indicator in this investigation. The results indicated that the highest and the lowest value of these yogurt in DPPH scavenging ability (88.50% of S2B3 and 86.16% of S2B2) and in hydrogen peroxide scavenging ability (14.28% of S2B3 and -1.78% of S1B1) were significantly different (p < 0.05). The shortest time needed to reach pH 4.6 (S1B1) was 529 minutes, and the longest one (S2B3) was 3336 minutes. Thus, S1B1 was regarded as the improved target in this investigation. Two Sc. cerevisiae (Y1 and Y2) were inoculated in milk with different temperatures (25, 37 and 43℃). The results showed that the Sc. cerevisiae fermented milk in the antioxidative ability, such as DPPH scavenging ability, hydrogen peroxide scavenging ability, ferrous chelating ability, superoxide anion scavenging ability and reducing power, achieved the peak after incubate 18 hours. Also, fermented milk inoculated with Y2 and incubated at 25℃ had the most appropriate condition. Finally, Y2 was mixed with yogurt (S1B1) by three various treatments. One of the ways, milk was incoulated with Sc. cerevisiae before incoulated with S1B1 (YL), had higher DPPH scavenging ability, ferrous chelating ability, reducing power, hydrogen peroxide scavenging ability, and superoxide anion scavenging ability than S1B1 (p < 0.05). YL had higher DPPH scavenging ability, ferrous chelating ability, and hydrogen peroxide scavenging ability than market product. The reducing power and superoxide anion scavenging ability in market product were higher than in Sc. cerevisiae yogurts. Hence, yogurt mixing with Sc. cerevisiae can increase antioxidative ability indeed.
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