Investigation of aflatoxins and toxigenic fungi contamination during post-harvest processing of Polygalae Radix / 中草药

ABSTRACT

Objective: To investigate aflatoxins contamination B1, B2, G1, G2 (AFB1, ATB2, AFG1, AFG2), toxigenic fungi species and potential contamination sources of Polygalae Radix during post-harvest processing, and analyze the main ways of aflatoxins contamination. Methods: Twenty-one Polygalae Radix samples were collected from multiple steps during the post-harvest processing in this study. Aflatoxin levels in these samples were determined by immunoaffinity column and HPLC coupled with post-column photochemical derivatization. Dilution-plate method was applied for the fungi isolation followed by strain identification based on morphological characterization and molecular approaches. Results: Aflatoxins were detected in 15 samples, but none of them exceeded the limit set by Chinese Pharmacopoeia. The fungal counts increased significantly from newly harvested samples to post-sweating, and the counts further increased to the maximum (2 × 108 CFU/g) after xylem-removing, then decreased after drying. In contrast, fungal counts of samples dried directly after harvesting did not change much throughout the processing. There was a significant positive correlation between fungal counts and water activity (Aw). A total of 209 fungal belonged to five genera were identified from the samples, and Penicillium was the predominant genus. Cladosporium and Fusarium were increased after sweating, and then Aspergillus increased after xylem-removing and drying. One A. parasiticus strain was confirmed to be able to produce AFB1, AFB2, AFG1, and AFG2. Conclusion: Aflatoxins contamination happened in both field production and post-harvest processing of Polygalae Radix. Especially, the contamination of Penicillium spp. should be paid more attention.