A polyphasic method for the identification of aflatoxigenic Aspergilla from cashew nuts

Area of Science:

• Food microbiology
• Mycotoxicology
• Molecular biology

Background:

• Toxigenic fungi in food pose significant public health risks.
• Cashew nuts are susceptible to fungal contamination and mycotoxin production.
• Accurate detection of aflatoxin-producing fungi and their toxins is crucial for food safety.

Purpose of the Study:

• To enumerate the microbial profile of cashew nuts.
• To detect aflatoxin-producing genes in isolated fungi.
• To quantify aflatoxin contamination levels in cashew nuts.

Main Methods:

• Utilized a polyphasic approach including novel β-Cyclodextrin Neutral Red Desiccated coconut agar (β-CDNRDCA) and Yeast Extract Sucrose agar (YES).
• Employed Thin Layer Chromatography (TLC), Polymerase Chain Reaction (PCR) for gene detection (aflM, aflD, aflR, aflJ, omt-A), and High-Performance Liquid Chromatography (HPLC) for quantification.
• Assessed aflatoxigenic potential and fluorescence enhancement on β-CDNRDCA.

Main Results:

• Isolated 63 fungal species from 18 genera; Aspergillus spp. were most prevalent (50.79%).
• Detected aflatoxin biosynthetic genes, with aflD amplified in all isolates and others in >70% of isolates.
• Quantified total aflatoxin content ranging from 0.03 to 0.77 µg/kg, below the EU limit of 4 µg/kg.

Conclusions:

• Cashew nuts analyzed had aflatoxin levels within safe limits.
• A combination of analytical methods is superior to single methods for comprehensive aflatoxin screening in food.
• The newly formulated β-CDNRDCA shows promise for detecting aflatoxigenic species.