Conclusion
Our study clearly showed that the methanolic extracts of cooked
non-fermented soybeans and their fermented counterparts (thua nao)
exhibited antioxidant and free radical scavenging properties. It was
also found that there was a strong relationship between total phenolic
contents and antioxidant activity (as determined by the β-carotenelinoleate
method). Moreover, the use of B. subtilis TN51 appears to
enhance phenolic amounts and increase antioxidant activity although
data of free radical scavenging assay were inconsistent. From our results,
it can be concluded that production process and bacterial fermentation
play the key role in improving these properties. Further study on (bio)
chemical characteristics of these antioxidative components as well as
their metabolic biotransformation remains to be investigated