The icddr,b scientists have revealed that more than 75 percent of all pasteurized milk available on the local market is unsafe for direct consumption.
However, this can only be dangerous if consumed 'raw' (not boiled), which is often practiced in Bangladesh, said the icddr,b revealing disturbing findings regarding commercially pasteurized milk which is the primary source of nutrition for children.
At every stages of the dairy value chain from the farm to store, milk is 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 Bagura.
Scientists found that at the primary producers lever, 72 percent and 57 percent milk samples collected were contaminated with coliform (≥ 100 CFU/ml) and faecal coliform (≥ 100 CFU/ml) bacteria, respectively and 11 percent of samples were contaminated with high number of E. coli (≥ 100 CFU/ml).
The faecal coliform bacteria is considered as a hygiene indicator and presence of these bacteria in the milk indicates that milk has 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 percent) while more than 40 percent 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 percent 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 (e.g. local restaurants).
Even more concerning is that scientists have found that about 77 percent of all pasteurised 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 percent and 15 percent of the same samples were found to be contaminated with coliform and fecal 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 pasteurized milk.
Speaking about what these findings mean to the consumer, Dr 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 samples from UHT milk were found to be devoid of any microbial contamination and 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 adds, "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 is also critical for ensuring safe milk for consumption, they said.
The research was 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.
Over 75% of all pasteurized milk unsafe: icddr,b