ELISA determination of Aflatoxin M₁ in milk and dairy products in Pakistan

Abstract

A highly sensitive competitive ELISA was standardized to determine aflatoxin M₁ (AFM₁) in milk and dairy samples randomly collected from Faisalabad city, using Riedel-de-Haen, Aflatoxin M₁ ELISA Systems, (Art–No. 45169). Standards of 5, 10, 25, 50, and 100 ng L⁻¹ AFM₁ in sample/standard buffer were used in optimizing anti-AFM₁ antibodies and peroxidase–AFM₁ conjugate. Linear standard curve showed increase in concentration (log C) accompanied by decrease in maximal absorbance (%B/B₀) values (%B/B₀ = 124.3 − 45.0 log C) with highly significant negative correlation (−0.973). The middle of the test (50% B/B₀) was at 30 ng L⁻¹ with 6.7 ng L⁻¹ the lowest detection limit (90% B/B₀). Duplicate analysis of 41 samples showed AFM₁ levels below EC permissible limits (50 ng L⁻¹) with maximums of 40, 13, and 7.4 ng L⁻¹ in milk, yogurt and butter, respectively. However, possibility of exceeding limits cannot be excluded, and demands regular monitoring.

Keywords:

• ELISA
• aflatoxin M₁
• monitoring
• milk
• yogurt
• butter

Acknowledgements

We thank the Pakistan Atomic Energy Commission (PAEC) for providing laboratory facilities at the Nuclear Institute for Agriculture and Biology (NIAB) Faisalabad, Pakistan. We thank SIGMA-ALDRICH Germany, for kindly providing the relevant ELISA kit for Aflatoxin M₁ free of cost.