Aflatoxin M1 Contamination of Milk and Its Products in Bomet County, Kenya

Aflatoxin M1 (AFM1) is a major carcinogenic compound that may be found in milk and dairy products resulting from ingestion of aflatoxin B1 by dairy animals. The study aimed at determining the level of aflatoxin M1 in milk and milk products from Bomet County. A total of 185 samples (150 raw milk and 35 processed milk and milk products) were randomly collected from milk collection sites and randomly selected milk kiosks respectively. The AFM1 was analyzed using a commercial ELISA kit (Ridascreen, aflatoxin M1 R-Biopharm, Product code, R5812, Darmstadt, Germany). Out of 185 samples investigated, 156 samples were positive for AFM1, an overall contamination rate of 84.32%. The samples with levels higher than the tolerance limit of 0.05 μg/l recommended by Food and Agriculture Organization (FAO) and World Health Organization (WHO) limits were 43.8% mainly contributed by the raw milk compared to processed milk (52.0% versus 8.6%). Processed milk had insignificant level of contamination with aflatoxin M1 (Median 0.00 (IQR: 0.00, 0.00 μg/l) with a minimum of 0.00 μg/l and a maximum of 0.69 μg/l. Raw milk showed significant contamination, median 0.09 (IQR: 0.00, 0.50) μg/l with a minimum of 0.00 μg/l and a maximum of 2.93 μg/l. Although there was no significant differences in AFM1 levels with study sites (P = 0.217);the median levels of aflatoxin M1 was high in sites 1, 3, and 7. The sites that had median aflatoxin M1 levels below the WHO/FAO acceptable limits of 0.05 μg/l were sites 2, 4 and 6. Due to high incidence of AFM1 contamination of milk and milk samples in Bomet County, there is need for regular monitoring and regulation of AFM1 contamination in milk and its products in the County.

An overview of aflatoxin B1 biotransformation and aflatoxin M1 secretion in lactating dairy cows

Milk is considered a perfect natural food for humans and animals.However,aflatoxin B1(AFB1)contaminating the feeds fed to lactating dairy cows can introduce aflatoxin M1(AFM1),the main toxic metabolite of aflatoxins into the milk,consequently posing a risk to human health.As a result of AFM1 monitoring in raw milk worldwide,it is evident that high AFM1 concentrations exist in raw milk in many countries.Thus,the incidence of AFM1 in milk from dairy cows should not be underestimated.To further optimize the intervention strategies,it is necessary to better understand the metabolism of AFB1 and its biotransformation into AFM1 and the specific secretion pathways in lactating dairy cows.The meta-bolism of AFB1 and its biotransformation into AFM1 in lactating dairy cows are drawn in this review.Furthermore,recent data provide evidence that in the mammary tissue of lactating dairy cows,aflatoxins significantly increase the activity of a protein,ATP-binding cassette super-family G member 2(ABCG2),an efflux transporter known to facilitate the excretion of various xenobiotics and veterinary drugs into milk.Further research should focus on identifying and understanding the factors that affect the expression of ABCG2 in the mammary gland of cows.

Removal of aflatoxin M1 from milk and aqueous medium by indigenously isolated strains of W.confusa H1 and L.plantarum S2

Employing LAB and/or their metabolites to reduce aflatoxins from food products is one of the fascinating areas of research.Therefore,in the present work an attempt was made to study the effect of isolated lactic acid bacteria(LAB)on the reduction of aflatoxin M1(AFM1)from phosphate buffer saline(PBS)and reconstituted skim milk(RSM).Out of 68 isolates,nine strains of LAB isolated from food products were examined to bind and reduce AFM1.The isolates were incubated with AFM1 at different time and temperature(24 h,48 h,and 72 h at 37℃ and 4℃)and later the residual toxin in the supernatant was determined.The preliminary results through thin layer chromatography(TLC)revealed that all isolates were able to bind AFM1 in PBS.However,based on the intensity of spots observed in TLC sheets,it was indicated that two isolates,H1 and S2 genotypically identified as W.confusa and L.plantarum shown better AFM1 binding ability as compared to other isolates.Further,the heat treated cells of both the selected strains did not show significant difference to AFM1 binding ability as compared to live cells.Results of high performance liquid chromatography(HPLC)observed that W.confusa H1 and L.plantarum had shown 78% and 72%AFM1 binding in PBS at 37℃ after 72 h.There was a significant difference(P<0.05)in AFM1 binding ability of L.plantarum S2 at 37℃&4℃,but such difference was not observed for W.confusa H1.Moreover,these isolates also observed reduction of naturally present AFM1 in 10%RSM.This is the first study reporting the AFM1 binding capability of the genus Weissella(strain W.confusa H1)and Enterococcus durans.These results showed that indigenous strains of LAB are able to bind AFM1 effectively.