| Summary: | 碩士 === 國立臺灣海洋大學 === 食品科學系 === 94 === Abstract
Lactic acid bacteria have been used lactic acid bacteria for improving the taste or storage on fermented products by people long time ago. Soy beans and related products contain a lot of healthy ingredients which have positive effectiveness on human. Therefore, the combination of products of lactic acid bacteria and soymilk could have benefits on improving human healthiness.
Lb. acidophilus CCRC 14079, Lb. bulgaricus CCRC 14009, Lb. fermentum CRL 251, Str. thermophilus CCRC 14085, B. infantis CCRC 14633, or B. longum B6 could be emplyeed for soymilk fermentation in order to reduce the unpleasant off-flavour resulted from oligosaccharides of n-hexanal and pentanal as well as effectively decrease contents of stachyose and raffinose which can cause flatulence in humans. The combination of cultures of LAB and bifidobateria to be used in starters for soymilk fermentation showed higher bacterial growth than individual starter used insoymilk fermentation.
The soymilk fermented with Bifidobacterium spp. by single culture of B. bifidum, B. breve Yakult, B. breve K-101, B. infantis CCRC 14633, B. longum, B. longum-a, B. pseudolongum, or B. thermophilum KFRI 00748 for 12-24 hours at 37oC could reach 7.6-9.0 log10 CFU/mL viable populations while the range of pH was 4.90-5.99. On the other hand, the soymilk fermented with Lb. plantarum KFRI 00144 or Lb. delbrueckii subsp. lactis KFRI 01181 at 37oC for 24 hours would reach the 4.7 and 4.4 of pH while the titratable acidity were 0.81% and 1.12% as well as the viable populations were 8.1 log10 CFU/mL and 9.1 log10 CFU/mL, respectively. These results suggested that soymilk is a kind of suitable media for growth of certain LAB.
It was identified that the soymilk fermented with combination cultures of LAB and bifidobacteria, especially the combination of Lb. acidophilus and B. longum had the highest effect, performed higher inhibition of ascorbate autoxidation than single culture did. After the soymilk fermented with LAB, their superoxide anion radicals scavenging effect increased from 32.44% to 43.08-65.04%. The soymilk fermented with combination of Str. thermophilus and B. infantis showed the highest antimutagenic activity, 85.07% and 85.78%, in all of the examined samples against two mutagens, NQNO and DMAB, respectively.
The quantities of daidzein and genistein in the fermented soymilk were increased which also resulting in higher antimutagenicity, antioxidant, and absorption rate in human bodies. For example, the soymilk fermented with B. breve YIT 4065 increased their total isoflavone from 1691.0 μg/mL to 1725.7 μg/mL. The quantities of glucosides are higher than aglycones before fermentation, and then the quantities of aglycones are higher than glucosides after lactic acid fermentation in soymilk. The amounts of daidzein and genistein in fermented soymilk will higher than unfermented soymilk about 17.11 and 69.48 times, respectively. These results indicated that β-glucosidase activity presented in fermentation could produce more bioactive aglycones.
The soymilk fermented with LAB showed no significant decreases both of viable populations and pH while it was stored at 4oC or 5oC for 14 days. The dried fermented soymilks with single culture of Str. thermophilus or B. longum presented higher viable populations as stored at 4oC than stored at 25oC for 4 months, and the freeze-drying fermented soymilk had higher viable populations and more stable pH value than spry-drying fermented soymilk did.
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