Aflatoxins and ochratoxin A in tea prepared from naturally contaminated powdered ginger

Abstract

The migration of several major mycotoxins, aflatoxins B₁ (AFB₁), B₂, G₁, and G₂ (AFT, total of the aflatoxins) and ochratoxin A (OTA), from naturally contaminated powdered ginger to surrounding liquid (tea) was investigated. The toxins are commonly found in cereal grains and are toxic, carcinogenic and thermostable. Ginger root is widely used for digestive problems. Powdered ginger (2 g) found to contain AFT and OTA was placed in an empty heat sealable tea bag. The tea bag was heat-sealed and used to prepare tea under different conditions: temperature (50 and 100°C), time (5 and 10 min) and volume (100 and 200 ml). The tea bag was placed in hot water and stirred every 1 min for 5 s during the first 5 min of steeping. After steeping, the tea bag was removed and the tea and ginger residue (in the tea bag) were analysed separately for AFT and OTA. After extraction and immunoaffinity column (IAC) clean-up, the isolated AFT and OTA were separated by reversed-phase liquid chromatography and quantified using a fluorescence detector. At 100°C, approximately 30–40% of AFB₁ and AFT and 20–30% of OTA in the contaminated ginger were found in the ginger tea; the total amounts of AFT and OTA in tea varied less than 5% under the three conditions of preparation. At 50°C, about 10% of OTA and AFT were found in tea. This is the first study on the migration of AFT from botanicals to tea. It is also the first to study the distribution of AFT and OTA from powdered ginger to tea and ginger residue.

Keywords:

• high-performance liquid chromatography (HPLC)
• aflatoxins
• ochratoxin A
• dietary supplements

Acknowledgements

This work was supported in part (interagency agreement) by the Office of Dietary Supplements, National Institutes of Health, Bethesda, MD, USA. The equipment used in part of this project was provided by the Fundação de Amparo à Pesquisa do Estado de São Paulo.