A new study conducted by icddr,b revealed that more than 75 per cent of all pasteurised milk available in the local market was unsafe for direct consumption.
However, this can only be dangerous if consumed ‘raw’ (unboiled), which was often done in Bangladesh, said the icddr,b, revealing disturbing findings regarding commercially pasteurised milk which was the primary source of nutrition for children.
At every stage of the dairy value chain from the farm to store, milk was found to be highly contaminated with bacteria above national and international standards, it said in a new study on Wednesday.
With the aim to assess the microbiological quality of milk at different stages of the dairy value chain, 438 raw milk samples were collected from milk producers, collectors, chilling plants, local restaurants in the northern part of Bangladesh.
Additionally, 95 samples were collected from commercially processed milk found on the shelves of local retail stores in Dhaka and Bogra.
Scientists found that, at the primary producer level, 72 per cent and 57 per cent of milk samples collected were contaminated with coliform (≥ 100 CFU/ml) and faecal coliform (≥ 100 CFU/ml) bacteria, respectively and 11 per cent of samples were contaminated with high number of E. coli (≥ 100 CFU/ml).
The faecal coliform bacteria was considered as a hygiene indicator and presence of these bacteria in the milk indicated that the milk had been contaminated with pathogens or disease producing bacteria or viruses, which can also exist in faeces of warm blooded animals, role of milking animal or the farmers to blame.
At the collection points, samples were found to be contaminated with a high number of coliform bacteria (≥ 100 CFU/ml) and faecal contamination (91 per cent) while more than 40 per cent of samples had a high E coli count.
At the chilling plants, collected samples were found to be contaminated even at a higher rate than that of collection points.
Samples from all 15 chilling plants distributed in five districts were contaminated with high number of coliform as well as faecal coliform. E coli was found in samples from all chilling points while 67 per cent of samples were contaminated with high level of E coli.
Presences of some other bacteria such as B cereus, staphylococci were also found in the samples but within normal limit. Bacterial counts in milk gradually increase from producers’ level to the chilling plants and to the consumers’ levels, for instance in local restaurants.
Even more concerning was that scientists had found that about 77 per cent of all pasteurised milk samples assessed had a high level of total bacterial counts (aerobic plate count) , which was beyond the BSTI (Bangladesh Standards and Testing Institution) standards of ≤2.0X104 CFU/ml. On the other hand, 37 per cent and 15 per cent of the same samples were found to be contaminated with coliform and faecal coliform bacteria, respectively.
Pasteurization is done to kill pathogenic bacteria to make the milk safe to consume. Both the national and international standards have zero tolerance for faecal coliforms in pasteurised milk.
Speaking about what these findings meant for the consumer, Mohammad Aminul Islam, associate scientist and head of the food microbiology laboratory at icddr,b and principal investigator of the study, said, ‘Raw or pasteurised milk available in the market are found to be contaminated with disease causing organisms and should not be consumed without thorough boiling.’
However, he said that samples from UHT milk were found to be devoid of any microbial contamination and was thus safe for direct consumption. ‘However, in this study we did not test the milk for chemical contamination or adulteration.’
Commenting on the dairy value chain assessment he added, ‘The presence of bacteria in milk at different stages indicates that the core quality of milk — its nutrition is highly compromised. Our studies show that several factors are involved in the contamination of milk at the primary producers’ level including the breed of the cow, volume of milk produced by the cow, the time of milking, and farmers hand washing practices.’
The scientists recommended that Bangladesh’s dairy companies should have end-to-end compliance of hygienic milking practices, collection and delivery, preservation and pasteurisation practices to ensure safe and nutritious milk for all.
Maintenance of seamless cold chain throughout the distribution channel of pasteurized milk from factory to consumer’s table was also critical for ensuring safe milk for consumption, they said.
The research was funded by CARE Bangladesh through its ‘Strengthening the Dairy Value Chain’ project and was conducted in 18 upazilas of Bogra, Gaibandadha, Nilphamari, Dinajpur, Joypurhat, Rangpur and Sirajganj.
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