Probiotic biological strategies to decontaminate aflatoxin M₁ in a traditional Iranian fermented milk drink (Doogh)

Aflatoxin M₁ is an important mycotoxin mostly found in milk and dairy products. The main objective of this work was to study the effects of probiotic strains, a probiotic inoculated population, the physiology of probiotic bacteria and final fermentation pH at four consecutive stages on the reduction of 0.500 ppb of free aflatoxin M₁ (AFM₁) in Doogh (a traditional Iranian fermented milk drink). Samples’ biochemical, microbial and AFM₁ binding characteristics were monitored during fermentation and storage (5 °C for 28 days). An immunoaffinity column was used to extract AFM₁ and a high-performance liquid chromatograph with a fluorescence detector was used to measure it. Results showed that Lactobacillus acidophilus was probiotic strain that most reduced free AFM₁. Inoculation of L. acidophilus at 9 log cfu/mL, despite the higher cost, revealed significantly higher free AFM₁ binding capacity than 7 log cfu/mL. Heat-killed (dead) L. acidophilus bacteria reduced less free AFM₁ at the end of storage than viable. Samples with a final fermentation pH of 4.5 bound more free AFM₁ during fermentation and storage than those with a pH of 4.2. It is concluded that inoculation of 7 log cfu/mL L. acidophilus viable cells in Doogh with a final fermentation pH of 4.5 supplied a safety- and health-promoting and cost-effective drink.