Prevalence Of Aflatoxin In Milk Sold Informally In Nairobi And The Effect Of Boiling And Fermentation

Abstract

It has been observed that milk in Kenya is contaminated with aflatoxin M1 which is transferred from the feeds consumed by the cows. This study was designed to assess the prevalence of AFM1 in raw milk informally sold in peri-urban Nairobi, assess knowledge of informal traders on aflatoxins and the effect of boiling and fermentation on the level of AFM1 found in milk. A baseline survey was carried out in Kasarani sub-County, Nairobi. Simple random sampling procedure was used to select interviewees for the study. A list of informal milk traders operating in Kasarani was established through the help of Sub-County administration, this formed the sampling frame. A sample of 96 milk traders in informal set-ups were randomly selected and interviewed face to face using pre-tested questionnaires. The aim of the interview was to establish socio-demographic, socio-economic, milk-sale characteristics and consumption characteristics, and knowledge on aflatoxins. The traders were also asked to describe how they carried out boiling of milk. Raw milk samples (n = 96) were collected from the interviewed traders and analyzed for AFM1 using ELISA method. Knowledge score was computed as a percentage of the sum of correct description and positive responses to the questions. Knowledge on aflatoxin was categorized into three; low knowledge (1 - 40%), medium knowledge (41 - 75%) and high knowledge (above 75%). xiv Boiling and fermentation trials using contaminated milk were carried out in the laboratory at the Department of Food Science, Nutrition and Technology, University of Nairobi. Boiling process was simulated in the laboratory according to the method described by traders. Fermentation was done by addition of starter culture to standardized milk after pasteurization at 90 °C for five minutes. Samples were taken during and after completing the process of boiling and fermentation. Samples were analyzed for AFM1 using ELISA. According to the survey, male traders comprised 51.5% while female traders comprised 48.5%. The mean age of the traders was 28.5 ± 14.5 years, (median = 33, range = 54). There was no significant difference in the age of traders between females and males (p = 0.89). On average, a trader’s household was described to have four members (median = 4, range = 9). A traders’ household averagely consumed 1.6 ± 1.4 (median = 1.0, range = 9.75) liters of milk in a day. Majority of the traders (61.5%) earned averagely below Ksh. 50,000 income monthly, while 12.5% earned between Ksh. 50,000 and 100,000 monthly. A small percentage (5%) earned above 100,000 monthly. About 20% of the traders could not tell how much they earned since they did not do frequent computations. The highest knowledge score among all traders was 65%. Most traders (69.8%) demonstrated low knowledge on aflatoxins while a lower percentage of the traders (30.2%) demonstrated medium knowledge. Knowledge was highly associated with education level and gender; traders that were more educated and female traders were more knowledgeable (p = 0.015 and p = 0.004 respectively). xv Most of the traders (61.5%) obtained milk from distributors coming from counties outside Nairobi. Results showed that all the milk samples (n = 96) were contaminated with AFM1 at a mean level of 290.3 ± 663.4 parts per trillion (ppt). About 66% of samples were above 50 ppt, the limit applied by the European Union (EU), while 7.5% of the samples exceeded 500 ppt limit applied in Kenya. Boiling trial showed no significant change on levels of aflatoxins (p = 0.42). Fermentation significantly reduced AFM1 during lala and yoghurt processing (p < 0.01). Reduction in AFM1 level was recorded for lala after incubation at room temperature for 15 hours was 71.8%; 73.6% reduction was recorded for yoghurt after incubation at 45 °C for four hours. The study concluded that knowledge on aflatoxin by informal milk traders was low and depended on education and gender. Informally marketed milk is contaminated by AFM1 at substantially high levels. Boiling does not reduce the level of contamination but fermentation reduces the level of AFM1 detectable in milk.