Removing aflatoxin M1 from milk with native lactic acid bacteria, centrifugation, and filtration

Abstract

In order to minimise human exposure to aflatoxin M₁ (AFM₁) the levels of this highly carcinogenic mycotoxin in milk, heat-treated milk, and other dairy products have been limited to <0.05 µg kg^-1. However, its removal from dairy products presents a challenge for dairy producers, as commercial additives change organoleptic properties, and filtration alone yields poor results. The aim of this study was to find a strain of lactic acid bacteria (LAB) from milk or dairy products that most effectively binds AFM₁ and to see whether heat treatment of the selected LAB affects the binding efficiency. We also wanted to investigate whether centrifugation can improve filtering of the obtained AFM₁-LAB complexes from milk. To do that, we isolated and identified 10 native LAB species/strains, incubated their viable or heat-treated cells (10⁸ CFU mL^-1) in milk spiked with 0.5 µg L^-1 of AFM₁ at 4 °C for 0, 2, 4, and 24 h, and quantified the amount of unbound AFM₁ with HPLC. AFM₁ binding efficiency ranged from 21 to 92 % for viable cells and from 26 to 94 % for the heat-treated ones. Since both viable and heat-treated Lactobacillus plantarum KM showed the best results, we used it for the next step in AFM₁ removal from milk. Heat treatment in combination with filtration and centrifugation yielded removal as high as 96 %.