Occurrence and potential health risk of aflatoxin M1 in raw, pasteurised, and UHT milk in Thailand

Abstract

Aflatoxin M1 (AFM1) is a major metabolite of aflatoxin B1 occurring in many feed materials commonly used in the ration of dairy cows. The level of contamination of feed materials is currently increasing in many parts of the world due to climate change. These changes emphasise the necessity to monitor AFM1 levels in milk and dairy products as a precautionary measure to protect consumer health risk. In the current study, the AFM1 levels were measured in raw, pasteurised, and ultra-high temperature processed (UHT) milk commercially available in Thailand. In total, 900 milk samples were analysed, making this investigation one of Thailand’s first large-scale monitoring of milk contamination. Over a period of three consecutive years (2019 to 2021), each year 100 individual samples of either AFM1, pasteurised and UHT milk were collected, extracted using an immunoaffinity column for AFM1 and then quantified by a validated liquid chromatography analysis with fluorescence detection. The measured AFM1levels ranged between 65-1,810 ng/l, 12-87 ng/l, and 7-38 ng/l in the raw, pasteurised, and UHT milk, respectively, in 2019. In 2020, the corresponding AFM1 concentration range was 58-1,232 ng/l, 15-65 ng/l, and 7-29 ng/l and 52-1,432 ng/l, 20-59 ng/l, and 7-33 ng/l in 2021, respectively. According to international guidance documents, a direct comparison and formal risk analysis revealed that the measured AFM1 levels of the processed milk samples showed good compliance with the US regulatory limits and the Codex Alimentarius Commission recommendations. However, the latter applies particularly to milk and dairy products intended for the consumption of infants and young children, considering their relatively high consumption of milk and dairy products and the specific sensitivity of infants and toddlers under the age of 6 years to mutagenic and genotoxic contaminants in foods.