3.2. Determination of total phenolic and specific
isoflavone contents
As shown in Table 1, total phenolic contents (TPC) in FSW and
USW extracts were 64.66 ± 2.79 and 52.79 ± 0.56 mg GAE/g
extract, respectively. The FSW extracts had significantly higher
TPC than that of unfermented samples. Microbial fermentation
significantly increased (p < 0.05) the TPC of the legume
products was also observed by Lee, Hung, and Chou (2008) and
Xiao et al. (2014). Chandrasekara and Shahidi (2012) also demonstrated
that phenolic compounds bounded to the insoluble
fiber were released during microbial fermentation. Lee et al.
(2008) demonstrated that β-glucosidase enzyme produced by
the organism during fermentation process was responsible for
polyphenol content enhancement. Dueñas, Fernández,
Hernández, Estrella, and Muñoz (2005) suggested that fermentation
by L. plantarum was an adequate process for improving
the concentration of phenolic compounds in fermented cowpea
(Vigna sinensis) flour. McCue, Horii, and Shetty (2003) reported
that the total soluble phenolic content increased by 120–
135% in the soybean seeds due to possible involvement of lignin
remobilization and/or degradation activities, as well as phenolic
detoxification activities, by microbial fermentation. Higher
TPC in fermented soy whey observed in our results might be
due to formation or mobilization of free phenolic and flavonoid
molecules during L. plantarum fermentation.