Fungal Contamination and FTIR-Based Metabolic Profiling of Mycotoxigenic Fungi in Tea Sold in Katsina Metropolis, Nigeria
TL;DR
Findings confirm that tea sold in Katsina Metropolis harbours potentially mycotoxigenic Aspergillus species and demonstrate that combining conventional microbiology, molecular identification and FTIR fingerprinting can support rapid, complementary screening of tea for fungal food-safety hazards, but direct mycotoxin quantification remains necessary to confirm actual toxin exposure risk.
Abstract
Tea is a widely consumed plant-derived beverage that can serve as a vehicle for fungal and mycotoxin contamination during production, storage, and retail. This study assessed fungal contamination in tea products retailed in Katsina Metropolis, Nigeria, and characterised the associated mycotoxigenic isolates using conventional, molecular and spectroscopic methods. Nine tea brands (coded A–I) were purchased from Katsina Central Market and subjected to serial dilution and plating on Potato Dextrose Agar to enumerate yeasts and moulds. The mean colony counts ranged from 35.0 ± 1.0 to 170.5 ± 10.5 at the 10⁻⁵ dilution and from 10.0 ± 1.0 to 99.5 ± 11.5 at the 10⁻⁶ dilution. Morphological examination and ITS rDNA sequencing identified the recovered isolates as Aspergillus niger, Aspergillus brasiliensis and Aspergillus flavus, with BLASTN sequence identities of 98.84%, 96.81% and 99.61% to reference GenBank accessions, respectively. Fourier-transform infrared spectroscopy of the three isolates produced distinct absorption bands corresponding to O–H, C–H, C=O and C–O functional groups, consistent with proteins, lipids and polysaccharides in the fungal biomass, with isolate-specific differences in peak position and intensity that distinguished the three species. These findings confirm that tea sold in Katsina Metropolis harbours potentially mycotoxigenic Aspergillus species and demonstrate that combining conventional microbiology, molecular identification and FTIR fingerprinting can support rapid, complementary screening of tea for fungal food-safety hazards. However, direct mycotoxin quantification remains necessary to confirm actual toxin exposure risk.