Natural occurrence of sterigmatocystin in in-shell pecans

Fungal Presence in Selected Tree Nuts and Dried Fruits

Sixty-four tree nut samples (almonds, pecans, pine nuts, and walnuts) and 50 dried fruit samples (apricots, cranberries, papaya, pineapple, and raisins) were purchased from local supermarkets and analyzed for fungal contamination using conventional culture as well as molecular methods. The results of our study showed that the highest yeast and mold (YM) counts (5.34 log₁₀ CFU g⁻¹) were found in walnuts and the lowest in pecans. The most common mold in nuts was Aspergillus niger, relatively low numbers of A. flavus were found across the board, while Penicillium spp. were very common in pine nuts and walnuts. Low levels (2.00–2.84 log₁₀ CFU g⁻¹) of yeasts were recovered from only two pine nut samples. Fungal contamination in dried fruits was minimal (ranging from <2.00 to 3.86 log₁₀ CFU g⁻¹). The highest fungal levels were present in raisins. All papaya samples and the majority of cranberry, pineapple, and apricot samples were free of live fungi. The most common mold in dried fruits was A. niger followed by Penicillium spp. One apricot sample also contained low levels (2.00 log₁₀ CFU g⁻¹) of yeasts.

Pine nuts: the mycobiota and potential mycotoxins

The mycobiota of pine nuts was investigated. In total, 1832 fungi belonging to 31 species and 15 genera (Ascomycota, 2; Zygomycota, 3; mitosporic fungi, 10) could be isolated. Cladosporium spp. dominated the mycobiota with 685 isolations followed by Phoma macrostoma with 351 isolations. Overall, 16 potentially mycotoxigenic species were present on pine nuts.Key words: pine nuts, mycobiota, potential mycotoxins.

Toxic aspergilli from pistachio nuts

Pistachio nut samples taken during various stages of development from orchards in Iran, showed that contamination with fungi occurred mainly during the later stages of nut development. Members of the genera Aspergillus and Penicillium occurred most frequently. Of the Aspergilli, the species A. niger, A. flavus and A. fischeri var. spinosus occurred most frequently, followed by A. terreus, A. tamarii and A. nidulans. Twenty-two isolates comprising 13 species were tested for toxicity to ducklings. Isolates of known toxic fungi included A. flavus, A. niger, A. parasiticus, A. ochraceus, A. versicolor, A. nidulans and A. terreus. The toxicity of A. fischeri var. spinosus is reported. Chemical analysis showed that all isolates of A. flavus and A. parasiticus produced aflatoxin B1, the isolates of A. versicolor and A. nidulans produced sterigmatocystin while the toxic isolate of A. ochraceus did not produce ochratoxins.