Detection of aflatoxin M₁ in milk, cheese and sour cream samples from Costa Rica using enzyme-assisted extraction and HPLC

Abstract

Aflatoxins are toxic fungal metabolites, which can be found in feed. Aflatoxin M₁ (AFM₁) is excreted into milk when ruminants ingest aflatoxin B₁ contaminated feedstuffs. Due to its carcinogenic potential, contamination of milk and dairy products with AFM₁ may pose a risk for consumers. Hence, it is considered a public health concern. In this survey, the level of AFM₁ contamination of dairy products marketed in Costa Rica was determined by enzyme-assisted extraction, immunoaffinity clean-up and high-performance liquid chromatography coupled with a fluorescent detector (HPLC-FLD) in fluid milk (n = 70), fresh cheese (n = 70) and sour cream (n = 70) collected at local convenience stores and supermarkets. AFM₁ concentrations in milk and fresh cheese ranged from 19 to 629 ng/L and from 31 to 276 ng/L, with mean values of 136 ng/L and 74 ng/L, respectively, whereas none of the sour cream samples analysed tested positive for this aflatoxin. In 30 milk samples, and 10 cheese samples, AFM₁ concentrations surpassed threshold concentrations as established by the European Commission. Thus, sour cream and – to a lesser extent – cheese manufacturing seems to reduce the amount of AFM₁ present in milk, possibly due to fraction redistribution or microbiological degradation. The survey results reveal improper quality control procedures in the Costa Rican dairy industry. Therefore, a surveillance programme for dairy products in our country is recommended.

Keywords:

• aflatoxin M₁
• milk
• sour cream
• cheese
• enzymatic extraction

Acknowledgements

The authors would like to thank Andrea Porras, Marisol Jiménez and Astrid Leiva for their excellent technical assistance. Jürgen Anthony is acknowledged for performing the NMR measurement. Special thanks to César Rodríguez for his valuable suggestions during the drafting of this manuscript. Vicerrectoría de Investigación supported this initiative by means of project B3097.