Monitoring of aflatoxin M1 in raw milk during four seasons in Croatia

Abstract

A total of 3543 raw cow milk samples were collected in three regions of Croatia: western, eastern and other regions during four seasons. Samples were measured for aflatoxin M1 (AFM1) concentrations using the enzyme immunoassay method. Elevated levels (>50 ng/kg) of AFM1 were analysed by validated liquid chromatography with triple quadruple mass spectrometry (LC-MS/MS). The limits of detection (LOD) and quantification (LOQ) of the LC-MS/MS method were 7.3 and 28 ng/kg, respectively. The mean AFM1 levels measured in the three regions over four seasons were in the ranges (ng/kg): eastern Croatia 7.25–26.6; western Croatia 5.91–9.26; other regions of Croatia 7.17–13.6. The highest incidence of samples exceeding the EU MRL (50 ng/kg) of 9.32% was measured in autumn (October–December) in the eastern region. Only eight samples were found to exceed the EU MRL in winter. The highest AFM1 levels were measured in December (764.4 ng/kg) and January (383.3 ng/kg). Elevated AFM1 levels were found in summer in only four samples from the western and other regions, and two samples in the eastern region. This can be attributed to localized and random usage of contaminated feed for dairy cows in those regions. The much lower incidence of elevated AFM1 in comparison to a previous study showed that the outbreak of the crisis due to elevated AFM1 levels in 2013 resulted in a more careful approach to the control of supplementary feedstuff for lactating cows.