Occurrence and Identification of Microbial Food Pathogens in Green Tea (Camellia sinensis): Influence on Catechins, Flavonoids, Phenolics, and Antioxidant Potential.

Abstract

Tea is the second most consumed beverage worldwide, with quality largely determined by phytochemicals, particularly catechins. However, its phytobiome comprising pathogens poses a major threat to tea quality and consumers' health. The current study is designed to systematically link environmental factors and processing conditions with tea quality by integrating microbiological, physicochemical, and phytochemical analyses. The microbial contaminants from leaves, tea infusion, and water used in the cleaning of tea processing machinery were isolated and identified through morphological, biochemical characterization, 16s rRNA sequencing. Aflatoxins in the final product were examined using high-performance liquid chromatography (HPLC). Additionally, tea catechins at different tea processing stages were quantified using ultraviolet-visible spectrophotometry, Fourier-transform infrared, and HPLC. Concurrent assessment of cultivable soil and water physicochemical parameters provided insight into how environmental inputs influence both microbial load and stability of catechins during tea processing. The study revealed a gradual decrease in catechins level (71.6%) throughout different tea processing stages (p < 0.05), consistent with presence of several microbial contaminants from the tea leaves and the water samples. Among the isolates, pathogens like Acinetobacter baumannii (12 × 10⁴ C.F.U/mL), Candida sp. (1.2 × 10⁵ C.F.U/mL), B. zhangzhouensis (1.5 × 10⁵ C.F.U/mL), Staphylococcus sciuri (4 × 10⁵ C.F.U/mL), etc., were detected in tea leaves while, Penicillium sp. (4 × 10² C.F.U/mL), Alcaligenes faecalis (4.3 × 10³ C.F.U/mL), and Sphingomonas paucimobilis (1.4 × 10³ C.F.U/mL), etc., were isolated from water samples. However, aflatoxins were absent, and no microbial contamination was detected in the tea infusion. Phytochemical evaluation across different stages of tea processing demonstrated that variation in environmental quality and hygiene practices could modulate catechin concentration. Overall, rolling, drying, and post-processing handling were identified as critical control points, demanding regulatory monitoring to ensure both the safety and quality of green tea. Collectively, the findings establish a clear interrelationship between environmental parameters, microbial dynamics involving pathogens, and phytochemical integrity, underscoring the need for integrated environmental and HACCP-based food safety management systems across cultivation and processing.