Quantitative analysis and dietary risk assessment of aflatoxins in Chinese post-fermented dark tea

Recently, mycotoxins safety in Chinese post-fermented teas has attracted much attention because it is still controversial whether environmental fungi in the teas are able to produce aflatoxins. In this study, a rapid and selective analytical method based on immunoaffinity column (IAC) cleaning coupled with liquid chromatography-mass spectrometry (LC-MS) was developed to quantify four aflatoxins (B₁, B_2, G₁ and G₂) in post-fermented teas. Recoveries ranged from 80.8 to 92.2% with relative standard deviation less than 3%. The limits of detection and quantification were 0.109–0.348 μg kg⁻¹ and 0.364–1.159 μg kg⁻¹, respectively. Two out of 158 samples were positive for aflatoxins examination (occurrence rate 1.27%). The deterministic assessment for the maximal aflatoxins exposure under upper bound was 9.19 × 10⁻⁶ μg kg⁻¹ day⁻¹ from heavy exposure consumers (≥50 year age group), but the exposure was lower than the JECFA acceptable value of 1.0 ng kg⁻¹ day⁻¹ on liver risk. Probabilistic assessment showed that the upper bound 95th percentile carcinogenic risk value for the 318 consumers (Yunnan China and Ulan Bator Mongolia) was 1.75 × 10⁻⁷, and for heavy exposure consumers was 2.4 × 10⁻⁷, and the values equally below the acceptable carcinogenic risk level.