Joshua et al. 2017

Abstract

Certain species of Aspergillus produce a toxic, carcinogenic and mutagenic compound, aflatoxin B₁ (AFB₁), and its metabolite aflatoxin M₁ (AFM₁) found primarily in milk as a result of hydroxylation of the parent compound (AFB₁) which is relatively stable in fresh and processed milk products, and has been showed to withstand pasteurization temperature. This study was carried out to evaluate the presence of AFM₁ contamination in raw and fermented milk. The analysis involved the use of competitive Enzyme Linked Immunosorbent Assay (c-ELISA) with the skimmed portion of the milk as test sample. The pH values of the milk were also measured using digital pH meter. Four hundred milk samples comprising of 100 fresh and 300 fermented from Kachia, Lere, Zaria and Sabongari local government areas. Of the 100 pooled fresh milk samples, 100% gave varying degrees of aflatoxin contamination from 1225 µg/l being the highest and to as low as 575 µg/l. Of the 300 pooled fermented milk samples, 96.6% showed varying degrees of aflatoxin contamination above the Food and Drug Administration, USA (FDA) regulation limit (500 µg/l) with 2050 µg/l being the highest. The highest pH value (5.96) was found in fresh milk (5.63-5.96) while fermented milk (3.58-4.08) showed the lowest pH value (3.58). In conclusion, the results showed that there is high contamination of cattle milk with AFM₁ in Kaduna state and an inverse proportional relationship between AFM₁ concentration and the pH values of the milk. The contamination will likely increase the risk of genotoxicosis and cancer development in the population.  Therefore, establishing, enforcing and monitoring the Nigerian AFM₁ regulatory limit based on our own data, ensuring proper storage of food stuff and proper inclusion of mycotoxin binders in animal feed production by commercial feed millers is inevitable to reducing the level of contamination.

Keywords: Aflatoxin M₁, Fermented milk, Fresh milk, Kaduna, Milk pH