Mycological Quality and Aflatoxin M1 Contamination of Milk and Milk Products from Bomet County, Kenya

Abstract

Milk and dairy products form essential constituents in daily meals of the residents of Bomet and other parts of Kenya. Dairy products are highly nutritious and may be susceptible to contamination by bacteria, molds and/or mycotoxins, and in particular aflatoxin B1 which is the most toxic. Aflatoxin M1 (AFM1) is a hepatic carcinogenic metabolite of aflatoxin B1 (AFB1) found in the milk or milk products obtained from livestock that have ingested feeds contaminated with AFB1. The aim of this study was to determine the mycological quality and aflatoxin M1 contamination of milk and its products from Bomet County, Kenya. A total of two hundred and twenty seven; (one hundred and ninety two raw and thirty five processed milk samples) were purchased from shops, milk vendors, kiosks and milk collection centers respectively. Isolation was done on Sabouraud Dextrose Agar (SDA) and identification was done using macro and micromorphological features and confirmed using Analytical profile index (API 20 C aux). Determination of aflatoxin M1 contamination was by direct competitive ELISA technique. Three hundred and sixty five fungal isolates of which 27(7.4%) were molds and 338(92.6%) yeasts were isolated from all the raw milk samples examined. Processed milk and its products showed no contamination with yeasts and molds. The isolated fungi belonged to the genera Aspergillus 3% (11/27), Geotrichum 4.1% (15/27) and Fusarium 0.3% (1/27), Candida 57.8% (211/365), Saccharomyces 6.6% (24/365), Cryptococcus 1.1% (4/365) and Rhodotorula 27.1% (99/365). Analysis of the data indicated that the overall occurrence of aflatoxin M1 contamination above the threshold limit of 0.05 ppb by Food and Agriculture Organization (FAO) and World Health Organization (WHO) limits was 43.8% (81/185). This was contributed mainly by the raw milk samples which had 52% (78/150) AFM1 contamination compared to processed milk with 8.6% (3/35). The difference was statistically significant, p<0.0001. The overall median was 0.02 (IQR: 0.00, 0.40) g / lwhich is below the threshold limits of 0.05 ppb by FAO/WHO. The levels of AFM1 in milk samples indicate that the feeds given to dairy cows in the study area could be contaminated with aflatoxin B1 which is the precursor of aflatoxin M1. This poses a potential risk of chronic exposure to the residents and therefore there is need for regular monitoring of contamination in milk and control most contaminating causes with special focus on occurrence of AFB1 in the feed of dairy cows. There is also need for awareness creation on aflatoxins in the to sensitize people on health hazards associated with aflatoxin M1 contamination as there may be chronic mycotoxin exposure.