| Summary: | 碩士 === 國立臺灣大學 === 食品科技研究所 === 92 === Abstract
Isoflavone is an important category of flavonoids and belongs to the phytoestrogen class. There are twelve major isoflavone isomers found in soybean. Isoflavone aglycones (daidzein, genistein and glycitein) are thought to be the most bioactive isomers among the isoflavones. This study investigated the changes of isoflavone composition and activity of β-glucosidase during the fermentation of soymilk with lactic acid bacteria (Streptococcus salivarius subsp. thermophilus BCRC 14085, Lactobacillus acidophilus BCRC 14079) and bifidobacteria (Bifidobacterium infantis BCRC 14633, B. longum B6) alone or simultaneously. On the other hand, the changes of isoflavone contents of the fermented soymilk products under different packaging and storage conditions were investigated.
The results showed that soymilk after fermentation, the contents of isoflavone malonylglucosides, acetylglucosides and β-glucosides decreased significantly. On the contrary, the amount of aglycones, (daidzein, genistein and glycitein) increased significantly. Among all the fermented soymilks tested, the greatest increase in the contents of aglycones and the highest β-glucosidase activity were noted in soymilk fermented with Streptococcus thermophilus, followed by that fermented with S. thermophilus and Bifidobacterium longum simultaneously. It was also noted that as the fermentation time was extended, the contents of aglycones and activity of β-glucosidase in soymilk was raised.
Fermented soymilks kept in dark glass bottles retained isoflavone contents much more than those kept in glass bottles exposure to light during the storage period. A better retention of isoflavone was noted in dried fermented soymilk that was held in dessicant and deoxidant containing bottle and stored at 4℃. On the other hand, retention of isoflavone in dried fermented soymilk was the poorest which was held in bottle without dessicant and deoxident and stored at 25℃.
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