Scientists at the International Centre for Diarrheal Disease Research, Bangladesh (icddr,b) have discovered that over 75% of all pasteurized milk in the market are unsafe for direct consumption.
The study has found that milk, in spite of being labelled as safe after undergoing pasteurization – a process which involves heating the milk to eliminate the bacteria and other germs – remains contaminated with bacteria far exceeding recommended quantities. Both the national and international standards have zero tolerance for faecal coliforms in pasteurized milk.
However, the bacteria are only harmful if consumed raw, i.e. unboiled, which is commonplace in Bangladesh in terms of packaged milk.
The scientists collected 438 samples from milk producers, collectors, chilling plants, and restaurants throughout northern Bangladesh. A further 95 samples were collected from commercially processed milk available at local retailers in Dhaka and Bogura.
The research, funded by CARE Bangladesh through its “Strengthening the Dairy Value Chain (SDVC)” project and was conducted in 18 upazilas of Bogra, Gaibandadha, Nilphamari, Dinajpur, Joypurhat, Rangpur, and Sirajgonj.
Rising bacterial levels across the chain of production
At the producer’s level, 72% of milk samples were contaminated with coliform bacteria (≥ 100 CFU/ml) and 57% were found to contain faecal coliform (≥ 100 CFU/ml). The dreaded E. coli bacteria (≥ 100 CFU/ml) was found in 11% of the samples.
Faecal coliform bacteria are considered hygiene indicators and their presence hints that the milk has been contaminated with pathogens.
At the collection points, 91% samples were found to contaminated with coliform bacteria and faecal contamination. The E. coli bacteria was found in 40% of the samples.
The samples from 15 chilling plants in five districts revealed a shockingly high 67% contamination with E. coli bacteria as well as significantly higher coliform and faecal coliform bacteria levels. Other bacteria such as B. cereus and staphylococci were also found but within normal limits. By the time the milk reaches a consumer, the bacterial count multiplies from the producer level.
Even more concerning is that scientists have found around 77% of all pasteurized milk samples assessed have a high level of total bacterial counts (aerobic plate count), which is beyond the BSTI (Bangladesh Standards and Testing Institution) standards of ≤2.0X104 CFU/ml.
On the other hand, 37% and 15% of the same samples were found to be contaminated with coliform and faecal coliform bacteria respectively.
To explain what these means, study lead Dr Mohammad Aminul Islam, associate scientist and head of the Food Microbiology Laboratory at icddr,b said, “Raw or pasteurised milk available in the market is found to be contaminated with disease causing organisms and should not be consumed without thorough boiling.
“However, samples from UHT milk were found to be devoid of any microbial contamination and are thus safe for direct consumption. But we did not test the milk for chemical contamination or adulteration during this research.”
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 cow breed, milk volume produced, time of milking, and hygiene among dairy farmers. We recommend that Bangladesh’s dairy companies develop end-to-end compliance of hygienic milking practices, collection and delivery, preservation and pasteurization practices to ensure safe and nutritious milk for all. Maintaining a seamless cold chain throughout the distribution channel of pasteurized milk from the factory to the consumer’s table is crucial to ensure safe milk for consumption.”