Abstract
M.Tech. (Biotechnology)
A number of spices and herbs are valued for their characteristic colour, flavour and aroma for both domestic and commercial applications either as ingredients for food preparation or for medicinal applications. They are largely grown in most African and Asian countries where favourable environmental conditions prevail for fungal and mycotoxin contamination of these spices. They are likely principal sources of mycotoxins, which are small molecular weight toxic secondary metabolites. With limited information on the occurrence of fungi and mycotoxins in food spices in South Africa, there is a need thus to establish levels at which fungi and mycotoxins contaminate such agricultural commodities in the country likely on a regular basis.
In this study, a QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) based extraction method was used to analyse 70 samples (5.0 g each) of dried food spices from one main distributor in South Africa [coarse chilli (n=14), ground chilli (n=4), paprika (n=7), ginger (n=5), chicken (n=8), onion (n=8), beef (n=5), Mexican chilli (n=9), vegetable (n=1), fruit chutney (n=4), and cheese (n=5)] consumed in South Africa for fungal and mycotoxin contamination. Liquid chromatography-tandem quadrupole mass spectrometer (LC-MS/MS) was used for the quantification and validation of 17 chemically distinct mycotoxins. Results obtained revealed the presence of the following mycotoxins: Total aflatoxins (AFs) (AFB1 + AFG1) (range: 2.6 - 18.5 μg/kg), ochratoxin A (OTA) (range: 5.8 - 20.0 μg/kg), total fumonisins (FBs) (FB1 + FB2)(range: 103.7 - 5897.2 μg/kg), sterigmatocystin (STE) (range: 18.3 μg/kg), 3-acetyldeoxynivalenol (3-ADON) (maximum level: 45.8 μg/kg), 15-acetyldeoxynivalenol (15-ADON) (maximum level: <LOQ), roquefortine C (ROQ C) (maximum level: 56.5 μg/kg), and citrinin (CIT) (maximum level: <LOQ). The study also revealed the findings that none of the samples analysed contained aflatoxin B2 (AFB2) and aflatoxin G2 (AFG2).
Similar samples were also analysed for fungal contamination using spread plate technique. Subsequently, fungal genera were identified by sequencing the ITS4 – ITS5 region and further confirmed for the presence of aflatoxin (AF), fumonisin (FB) and ochratoxin (OT) producing fungi following a PCR- and QPCR-based technique. Fungal contamination levels were established and expressed in colony forming units per gram (cfu/g) of sample. Data obtained revealed a total of 29 fungal isolates recovered from samples belonging to the Aspergillus, Penicillium, Allophoma and Phoma genera. This varied among the spices with the highest...