Validation of an ELISA test kit for the quantitative analyses of total Aflatoxins in spices marketed in Cameroon

Aflatoxins (mold-synthetized secondary metabolites) contamination associated with food such as spices continue to be a global problem in the world. The aim of this study was to measure the standard parameters of validation (Linearity, occuracy, repeatability, intermediate precision, reproducibility, limit of detection, limit of quantification and robustness) of the total Aflatoxins (AFt) low-matrix Enzyme-Linked ImmunoSorbent Assay (ELISA) Kit (Lot No. 062218, RENEKABIO, USA) and used this method to evaluate the contamination degree of AFt ( AFB1, AFB2, AFG1 and AFG2) in 4 different spice matrices [white pepper (Piper nigrum), black pepper (Piper nigrum), njansang (Ricinodendron heudelottii) and super épice mbongo  ( Mix of Aframomum citratum, Monodora myristica and Afrostyrax lepidophyllus] marketed in Cameroon and commonly used as ingredients in Cameroonian sauces. The test was performed as a solid phase direct competitive ELISA using a horse radish peroxidase conjugate as the competing, measurable entity.

Data obtained from validation showed linearity in the range between 0 mg kg-1 and 20 mg kg-1; an accuracy marked by a recovery rate ranging from 95.09 % to 110.29 %; a coefficient of variation (CV) of repeatability of 3.14 %, a coefficient of variation (CV) of intermediate precision of 6.82 % and a coefficient of variation (CV) of reproducibility of 13.96 %. Detection and quantification limits of 0.15 mg kg -1 and 0.50 mg kg -1 were determined, respectively. The robustness test revealed a critical point of the method as an incubation for 30 minutes at room temperature. The application of the method to our spices analyzed revealed 100 % contamination of 2.34 ± 0.25 µg kg -1 (white pepper), 2.37 ± 0.38 µg kg -1 (black pepper), 2.58 ± 0.87 µg kg -1 (Njansang) and 6.60 ± 5.21 µg kg -1 (Super épice mbongo).

The RENEKABIO low matrix ELISA kit used for this research enables an accurate, reliable and faithful screening and quantification of AFt in spice matrices. This will be an asset in quality control of spices marketed in Cameroon.