Microbial profiling of bold green tea bottled beverages: A screening experiment

Objectives

To explore the storage potential and drinking safety of leftover bottled tea beverages from various manufacturers after directly drinking from the bottle, we conducted a screening experiment on the growth of salivary bacteria in plastic bottles of bold green tea.

Methods

Resting whole saliva (n = 14) was collected from each participant (aged 19–25 years). The saliva samples (1.0 mL of each diluted saliva sample [5.0 × 10⁵ CFU/mL]), were inoculated into plastic bottles containing 280 mL of green tea, which included six types of bold green tea beverages. The bottles were stored at 37 °C for 24 h; subsequently, 1.0 mL of each sample was inoculated onto a blood agar plate and incubated anaerobically at 37 °C. Genomic DNA was extracted from the resulting individual colonies and the bacterial species were identified by 16S rDNA sequencing.

Results

More than 60 % of the samples of six types of bold green tea beverages, Bold Oi Ocha®, Suntory Bold Green Tea Iyemon®, Bold Oi Ocha Premium Strong®, Healthya®, Bold Ayataka®, and Catechin Green Tea® showed low bacterial levels (<10³ CFU/mL) after 1 day of storage. However, in some cases, former members of the genus Lactobacillus, such as Limosilactobacillus and Lactiplantibacillus spp., were specifically detected as the predominant bacteria (37.6–100 %), although these bacteria usually account for the minority among the oral microbiome.

Conclusions

Although the antibacterial effects of catechins may have affected the total bacterial counts and compositions, no clear correlation was observed between total tea catechin concentrations and total bacterial growth inhibitory effects.