Characterization and ACE Inhibitory Activity of Fermented Milk with Probiotic K25 as Analyzed by GC-MS-Based Metabolomics Approach.

Addition of probiotics to yogurt with desired health benefits is gaining increasing attention. To further understand the effect of probiotic on the quality and function of fermented milk, probiotic fermented milk (PFM) made with probiotic K25 and yogurt starter ( ssp. and ) was compared with the control fermented milk (FM) made with only the yogurt starter. The probiotic strain was shown to survive well with a viable count of 7.1 ± 0.1 log CFU/g in the PFM sample after 21 days of storage at 4°C. The strain was shown to promote formation of volatiles such as acetoin and 2,3-butanediol with milk fragrance, and it did not cause post-acidification during refrigerated storage. Metabolomics analysis by GC-MS datasets coupled with multivariate statistical analysis showed that addition of K25 increased formation of over 20 metabolites detected in fermented milk, among which γ-aminobutyric acid was the most prominent. Together with several other metabolites with relatively high levels in fermented milk such as glyceric acid, malic acid, succinic acid, glycine, alanine, ribose, and 1,3-dihydroxyacetone, they might play important roles in the probiotic function of K25. Further assay of the bioactivity of the PFM sample showed significant ( < 0.05) increase of ACE inhibitory activity from 22.3% at day 1 to 49.3% at day 21 of the refrigerated storage. Therefore, probiotic K25 could be explored for potential application in functional dairy products.