The mycofloras and potential for mycotoxin production of various samples of green, fermented and late fermented tea

The fungal populations of ten tea samples and one of fresh leaves of tea were enumerated by dilution plating onto three different media (Malt chloramphenicol agar, Dichloran rose bengal chloramphenicol agar and Dichlorane glycerol agar). The fresh leaves yielded fairly high numbers of fungi, Cladosporium cladosporioides and pink yeasts being the most common. Seven of the 10 teas gave low counts of less than 5.0×102 colony forming unit (C.F.U.) g-1 fresh weight and this included all the black teas. The Goishi-cha, late fermented tea, gave 1.5×103 C.F.U. g-1 consisting entirely of one mycelial yeast species. A sample of chinese Pu-erh tea yielded the richest flora of about 4.1×103 C.F.U. g-1 dominated by two Aspergillus species, A. versicolor and A. sydowii. One of A. versicolor isolates produced sterigmatocystin (STG) on shredded wheat medium (SWM). None of A. sydowii isolates produced STG on either glucose yeast extract (G-Y) medium or SWM. Although one of the A. versicolor isolates was found to be a toxigenic strain (by growth on SWM) it did not produce STG on green tea.