P1-135 An Experimental Study on Aflatoxin M1 Binding by Probiotic Bacteria in Yogurt

Monday, July 23, 2012
Exhibit Hall (Rhode Island Convention Center)
Guity Karim, University of Tehran, Tehran, Iran
Mahsa Tabari, Islamic Azad University, Lahijan, Iran
Introduction:   Mycotoxins are of great concern because of their acute and long-term toxicity. Aflatoxin M1 is an important mycotoxin frequently found in milk and dairy products. The exposure of some bacterial strains might affect and cause a reduction in the concentration aflatoxin M1.

Purpose:  The aim of this study is to investigate and understand the behavior of two probiotic bacterial strains; Lactobacillus acidophilus LA5, Bifidobacterium animalis/lactisBB12 in corporation with yogurt starters to eliminate aflatoxin M1 in yogurt.

Methods:   High Performance Liquid Chromatography equipped with fluorescence detector was used to determine Aflatoxin M1 in yogurt. The method was optimized and validated according to Commission Decision BS EN ISO 14501:2007 by using the conventional validation approach, according to the standard, selectivity, recovery, and precision of the method.

Standard samples of known aflatoxin M1 concentrations (0.1 to 10 µg/l) were injected and a linear calibration curve was obtained. In order to validate the method, the mean recoveries were calculated at three different levels of aflatoxin M1 additions (0.5, 1.0, and 1.5-fold the MRL).

Later reconstituted milk with added aflatoxin M1 at concentrations of 0.050 and 0.100 µg/l was fermented with two probiotic bacteria (Lactobacillus acidophilus LA5, Bifidobacterium animalisBB12) in corporation with yogurt starter cultures to reach pH value of 4.6. The prepared yogurt samples were stored at 4 °C for 4 weeks. Qualitative and quantitative tests concerned with aflatoxin M1 were performed by the application of HPLC using validated method.

Results:   The results show that the calibration curve was linear for the concentrations of 0.1–10 µg/l when injected. The average recoveries were determined on three different days for various concentrations (0.025, 0.050, 0.075 µg/kg) in septimal orders (72.57 – 86.66%) with RSD in the range of 2.56 – 8.41 %. The limit of detection (LOD) and limit of quantitation (LOQ) values were 0.006 µg/kg and 0.015 µg/kg, respectively. The method was not affected by slight variations of some critical factors as pre-treatments and different storage conditions.

The results of the validation and the method used are in agreement with method described by Commission Regulation 401:2006: EC which might be regarded rapid, reproducible and simple to apply.

AFM1 levels in yogurt samples showed a significant decrease (P < 0.01) as compared to those initially added to milk. The growth of lactic acid bacteria was not affected by the presence of aflatoxin M1 except Streptococcus thermophilus that showed a significant (P < 0.01) decrease in the yogurt containing the toxin at high concentration. During the course of fermentation, AFM1 was significantly decreased (P < 0.01) in yogurts at both contamination levels; however, storage at refrigerated conditions did not affected the levels of aflatoxin significantly (P > 0.01). Final loses of 33 to 39% were observed at the end of both fermentation and refrigeration practice. 

Significance:   It therefore might be suggested that the strains of probiotic bacteria which were studied in this research work and are currently used in the food industries, due to their cost-effective and detoxification potentials employed at great demand for decreasing of aflatoxin M1 level in milk products.