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Commercial green tea from Portugal: Comprehensive microbiologic analyses.
Carla Viegas1, Flávio Sá2, Margarida Mateus2
1H&TRC- Health & Technology Research Center, ESTeSL- Escola Superior de Tecnologia da Saúde, Instituto Politécnico de Lisboa, Portugal; NOVA National School of Public Health, Public Health Research Centre, Universidade NOVA de Lisboa, Portugal; Comprehensive Health Research Center (CHRC), Portugal.
Green tea (GT) bioburden was assessed, revealing bacterial and fungal contamination in both bulk and bagged forms. Boiling significantly reduced bacteria but not potentially toxigenic fungi, necessitating further mycotoxin analysis.
Area of Science:
- Microbiology
- Food Science
- Public Health
Background:
- Green tea (GT) consumption is rising due to documented health benefits.
- Assessing microbial contamination in GT is crucial for consumer safety.
- Limited data exists on the fungal burden and azole resistance in marketed GT.
Purpose of the Study:
- To evaluate the bacterial and fungal bioburden in bulk and bagged GT sold in Lisbon.
- To characterize fungal contamination, including azole resistance.
- To assess the impact of boiling on microbial load and identify potential risks.
Main Methods:
- Microbiological analysis of bacterial and fungal counts in GT samples (bulk and bagged) before and after boiling.
- Fungal identification using culture-based methods and real-time PCR.
- Azole resistance profiling of fungal isolates.
Main Results:
- Bacterial contamination varied significantly, with boiling reducing counts in brewed samples.
- Fungal contamination, primarily Aspergillus section Nigri, was present in both bulk and bagged GT, persisting after boiling.
- Higher fungal diversity was observed in bulk GT compared to bagged GT.
- Some fungal species showed growth on azole-supplemented media, indicating potential resistance.
Conclusions:
- Boiling effectively reduces bacterial load in GT but not all fungal contaminants.
- Potentially toxigenic fungi can be present in GT before and after boiling.
- Further research on mycotoxin contamination is essential for a comprehensive risk-benefit assessment of GT consumption.
- Packaging conditions may influence fungal diversity in GT.