Microbial contamination and mycotoxins from nuts in Riyadh, Saudi Arabia.

摘要

Forty samples of edible nuts and dried seeds were randomly collected from different locations in Al-Riyadh, Saudi Arabia, and analysed for contamination by bacteria, fungi and mycotoxins. Fungi were detected by seed-plate and dilution plate methods and were cultured on glucose-Czapek's agar, sucrose-Czapek's agar and starch yeast agar. Purified fungal isolates were identified morphologically. Mycotoxins were extracted using chloroform and detected by TLC. Bacterial analysis was conducted using the total plate count (TPC) method. The predominant microbial contaminants were Aspergillus niger and A. flavus. Highest levels of fungal contamination were observed in pumpkin seeds, followed by peanuts, pistachios and chick peas. Aflatoxin B1 (8.5 mug ml--1) was detected in peanuts containing A. flavus. Aflatoxin B1 (1.7 mug ml--1) and B2 (1.7 mug ml--1) were detected in sunflower seeds containing A. terreus. T2 toxin (2.8 mg ml--1) was detected in pumpkin seeds containing Stachybotrys chartarum and DAS (2.4 mug ml--1) was detected in a salted peanut sample containing Trichthecium roseum. 4 nut samples were contaminated with bacteria. Relatively high total plate counts were observed in Turkish pine seeds, American walnuts, Pakistani pine seeds and Iranian salted pistachios, and Listeria monocytogenes was isolated from American walnut samples.