Effect of preservatives on immunoenzymatic methods for the analysis of aflatoxin M1 in ewe's milk

In line with Spanish regulations (RD 1728/2007), milk samples collected from dairy farms can be preserved by adding Azidiol (Az) before quality control analyses in the laboratory. Sometimes, these samples arrive at the laboratory with another preservative, such as Bronopol (Br), but these are less common circumstances. When ewe's milk is analysed for the detection of aflatoxin M1 (AFM1) within a quality control programme, several methods could be used, such as ELISA (Enzymed-Linked ImmunoSorbent Assay) kits. Should some preservative have been added to milk, it is unknown whether these assays could be affected. The objective of this experiment was to prove whether some preservatives (Az or Br) could alter the detection of AFM1 in ewes' milk when ELISA tests were being used for the analysis. Two different commercial ELISA kits were chosen. Based on the results of this work, the combination of preservatives and refrigeration could slightly interfere with the recovery of AFM1 by immunoenzymatic tests, mainly in the case of Bronopol.