Assessment of aflatoxin B1 content and aflatoxigenic molds in imported food commodities in Muscat, Oman

Aflatoxins, mainly produced by Aspergillus flavus and A. parasiticus are considered as serious food safety and human health issues due to their hepatotoxic effects. In the present study, the occurrence of aflatoxin B1 (AFB1), the most potent human liver carcinogen, and prevalence of toxigenic isolates of Aspergillus spp. were assessed in 140 food commodities in Muscat markets, Oman, and the 95 quarantined imported food commodities. These samples consisted of rice, corn, peanut, red chilli powder, soybean, dried dates and tree nuts. AFB1 was analyzed using competitive ELISA/LC-MS and the aflatoxigenic fungi were detected using plating technique followed by molecular identification. No AFB1 was detected in 89 (63.6%) samples collected from local markets, while 44 (31.4%) samples contained 1-5 ppb and the remaining 7 (5%) samples (red chili powder) contained 6-10 ppb. None of the samples exceeded the maximum permissible limit of 10 ppb set for foods by Oman legislation. Of the 95 quarantined samples, only 17 (17.9%) samples were positive and contained AFB1 at concentrations ranging from 1-3.4 ppb. Four isolates of Aspergillus pp. were isolated from the collected samples and were identified as Aspergillus flavus (A14, A16 and A23) and A. chevalieri (A46) on the basis of internal transcribed spacer (ITS) sequences of ribosomal DNA. Among them, A. flavus strain A14 alone produced AFB1 (7.6 ppb), while A16, A23, and A46 were non-toxigenic. This is the first detailed report on the occurrence of AFB1 in food commodities imported into Oman

Antifungal Activity of Shirazi Thyme (Zataria multiflora Boiss.) Essential Oil against Hypomyces perniciosus, a causal agent of wet bubble disease of Agaricus bisporus

Wet bubble disease (WBD) caused by Hypomyces perniciosus is a major constraint of button mushroom (Agaricus bisporus) cultivated worldwide. A few synthetic chemical fungicides are used to control WBD. In our study, the potential of essential oil (EO) from Zataria multiflora in inhibition of H. perniciosus was evaluated as an alternative to chemical fungicides. An isolate of H. perniciosus was isolated from wet bubble diseased A. bisporus and pathogenicity of the mycoparasite was determined under artificially inoculated conditions. The mycoparasitic fungus was identified using sequences of the internal transcribed spacer (ITS) region of ribosomal DNA. The EO was extracted from the aerial parts of Z. multiflora by microwave extraction method and evaluated in vitro for its antifungal activity against H. perniciosus. The EO of Z. multiflora (ZEO) at the tested concentrations (50% and 100%) inhibited the growth of H. perniciosus in the agar diffusion test. The minimum inhibitory concentration (MIC) of ZEO was 0.04% as assessed by the poisoned food technique. The chemical composition of ZEO was determined by gas chromatography-mass spectrometry analysis. A total of 23 compounds were identified. Among them, the most abundant compounds were Linalool (20.3%) and Bornyl acetate (15.5%). Linalool at the tested concentrations of 0.25% and 0.125% completely inhibited the mycelial growth of H. perniciosus in an in vitro assay. These results suggest that ZEO can be exploited for control of WBD