Aflatoxin B1 and sterigmatocystin: method development and occurrence in tea

Tea is one of the most popular beverage in the world and may be contaminated by fungi and mycotoxins during processing. To analyse aflatoxin B1 (AFB1) and sterigmatocystin (STC) in three types of tea, a simple, fast, sensitive and reliable method of these two myxotoxins was developed. Recoveries obtained ranged from 95.9% to 118.0% and the RSDs were between 0.3% and 11.2%. The range of LODs was 0.2–0.45 µg/kg for AFB1 and 0.04–0.12 µg/kg for STC. The range of LOQs was 0.67–1.73 µg/kg for AFB1 and 0.13–0.40 µg/kg for STC. The optimised procedure was applied to analyse 126 tea samples randomly collected from different markets in China. AFB1 was not detected, but STC was determined in 17 samples with concentrations ranging from 0.13 to 4.48 µg/kg. The detection rate of STC was 5%, 8.9% and 33.3% in black tea, green tea and Oolong tea, respectively.