Fungal diversity and mycotoxin contamination in dried fish products in Zhanjiang market, China

Abstract

Dried fish are important dietary protein and income sources in Zhanjiang, China. Mycotoxins produced by pathogenic fungi that contaminate fish during processing can cause considerable hazard to consumer health. This study reports fungal diversity, total fungal counts and mycotoxin contamination of dried fish sold at the seafood market in Zhanjiang. Seven dried fish products (Hemibarbus maculatus, Pseudosciaena crocea, Lutjanus erythopterus, Thunnus thynnus, Scomberomorus niphonius, Eleutheronema tetradactylum, Trichiurus lepturus, n = 10) from seven retailers were analyzed for contaminated fungal species, occurrence frequency and residues analysis of four mycotoxins. Using potato dextrose agar (PDA) plate purification, morphology observation, internal transcribed spacer (ITS) sequence analysis, 25 fungal strains representing 12 genera from dried fish were systematically isolated and identified. Three dominant genera in dried fish were Fusarium sp. (80.4%), Penicillium sp. (70.7%) and Aspergillus sp.(63.9%). Other fungal genera were Neoscytalidium sp.(38.1%), Cutaneotrichosporon sp. (38.1%), Trichoderma sp.(20.3%), Naganishia sp.(15.3%), Kodamaea sp. (10.8%), Phialemoniopsis sp.(9.2%), Nigrospora sp.(7.3%), Ceriporia sp.(6.3%), Phellinus sp.(4.5%). Aspergillus flavus contamination was the higher and ranged from 1.10 × 10³ to 2.40 × 10⁴ cfu/g. The mean fungal contamination of other fungal species in dried fish ranged from 1.07 × 10² to 4.58 × 104 cfu/g. The total fungal counts of Fusarium sp. ranged from 1.09 × 10² to 2.11 × 10⁴ cfu/g, but the occurrence frequency is relatively high. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses showed that mycotoxin residues were present in 12 out of the 25 dried fish tested. Aflatoxin B1 (AFB₁) was the most frequently detected and the concentration ranged from 0.03 to 3.52 μg/kg. T-2 toxin (T-2), ochratoxin A (OTA), and deoxynivalenol (DON) concentrations ranged from 0.21 to 1.53, 0.03–2.21 and 0.71 μg/kg respectively. High occurrence of fungal populations and mycotoxins in dried fish sold in the Zhanjiang market pose a potential threat to consumer health. It is recommended that in future, advanced processing methods and controlled storage condition need to be used to minimize and if possible eliminate fungal contamination during dried fish processing.