Fallacies about Unprocessed Milk

'Be safe! Buy processed milk!' This is the clarion call of the Kenya Dairy Board, Kenya Bureau of Standards and Ministry of Health in a series of recent television advertisements. This comes in the light of widespread purchase of raw milk by the consumer and is aimed at encouraging them to opt for factory-processed milk instead.

But one may ask: What is the danger in unprocessed milk? Raw milk is a microbial hazard because its chemical composition is an ideal growth medium for many spoilage micro-organisms. It may also harbour pathogens that cause milk-borne diseases such as brucellosis and tuberculosis. However, heat effectively kills pathogenic micro-organisms and is the method of choice in processing raw milk. Pasteurisation is a form of heat treatment aimed primarily to destroy pathogens.

The temperature-time regime commonly used in industrial operations is 72 degrees centigrade for 15 seconds, after which the milk must be cooled immediately to below 10 degrees centigrade to inhibit growth of heat-tolerant micro-organisms not destroyed in the pasteurisation process. These organisms can survive exposure to high temperatures but do not necessarily grow at these temperatures. Therefore, they can spoil pasteurised milk by causing undesired curdling. Conversely, boiling destroys all living microbial cells in milk. Since pasteurisation is a milder heat treatment, the heat-sensitive vitamins are preserved in pasteurised milk, unlike boiling. However, Kenyans often boil milk before drinking it, purchased raw or pasteurised, so these vitamins end up being destroyed either way and must be sourced from other foods.

So, the question arises: Is factory-processed milk any safer than raw milk boiled at home in a sufuria (pan)? This safety concern gained momentum and precedence after a countrywide increase in raw milk sales following the liberalisation of the dairy industry in 1992. Key stakeholders in the sector surmised that raw milk possibly posed a significant public health risk to consumers.

To come up with scientific evidence on the status of milk-borne health risks in Kenya, a study was carried out in 1999/2000 by the Smallholder Dairy Project (SDP) involving a team from the Kenya Agricultural Research Institute (KARI), the Ministry of Agriculture and Rural Development and the International Livestock Research Institute (ILRI). Scientists from the University of Nairobi's Department of Veterinary Public Health, Pharmacology and Toxicology and the Kenya Medical Research Institute (KEMRI) collaborated. Consultation was sought from the Kenya Dairy Board and the Kenya Bureau of Standards (KEBS) before and during the project. The study was carried out in four districts: Nairobi and Kiambu - representing areas of high human and cattle population densities with intensive dairy production systems, and Narok and Nakuru - representing extensive dairy production areas with low human and cattle population densities.

About 1,000 samples of raw and pasteurised milk were collected from randomly selected households, dairy cooperatives, self-help groups, milk bars, kiosks, mobile traders (milk 'hawkers') and retail outlets. Among the data obtained was information on preferred sources of consumed milk, its microbiological quality, the presence of antibiotic residues and handling practices by milk traders. It was found about 90% of milk was sold unpasteurised, either directly to consumers or through milk 'hawkers'. Most consumers preferred to buy unpasteurised milk because processed milk was costly.

However, despite this widespread buying of potentially harmful raw milk, all sampled urban households and 96% of sampled rural households were reported to boil before drinking it, often together with tea leaves. This effectively eliminated the pathogen hazard. A small proportion (6%) of rural households were reported to consume home-made naturally fermented milk.

The results of tests on the bacteriological quality of the milk revealed that most samples, raw or pasteurised, did not attain their respective standards for total and coliform counts, as specified by the Kenya Bureau of Standards (KEBS). High total bacterial counts may indicate prolonged storage at high temperatures, while the presence of coliforms indicates poor hygienic handling and possible faecal contamination.

The key factors noted to contribute to failure to attain microbiological quality standards were long market chains, poor hygiene and high ambient temperatures (particularly if milk was not chilled). The KEBS standards are based on those operating in countries where milk is chilled on the farm and always pasteurised before sale. Thus, a review of local milk quality standards is recommended, taking into account the widespread lack of cold-chains for milk marketing, prevalent sale of raw milk and the consumer's common practice of boiling milk before drinking it. Training and certification of handlers is vital for reducing coliform contamination. Another potential risk observed was the presence of antibiotic residues in 6% and 8% of raw and pasteurised milk samples, respectively. Such residues can arise due to poor practices at the farm level and failure to adhere strictly to specified milk withdrawal periods after antibiotic treatment of dairy cows.

The presence of antibiotic residues in foods contributes to long-term bacterial resistance to common antibiotics. This points to a need to reinforce the training of dairy farmers on good animal husbandry. Regarding raw milk handling practices, it was noted that small-scale milk traders used non-food grade plastic containers more often than not, unlike the larger dairy cooperatives, which tended to use sterilisable aluminium churns. Around 80% of all raw milk outlets did one or more quality tests before receiving the milk.

Contrary to a common perception, there was hardly a case of raw milk adulteration through chemical preservatives, such as hydrogen peroxide, to increase its storage life. Instead, what was observed was awareness of the importance of reducing contamination and improving hygiene. About 90% of raw milk traders indicated that they used hot water and soap/disinfectant to clean containers. Such a positive mindset needs to be reinforced with appropriate training, which was identified as an immediate need.

Only 12% of all raw milk handlers said they had received any form of training in hygienic milk handling and quality assurance, although this was wide-ranging, from 4% of mobile milk traders to 43% of dairy cooperative personnel. However, the report notes that the first step to improve milk hygiene is to recognise the small-scale trader's important role in marketing milk. An urgent review of the Dairy Act is imperative to take such traders into account. Efforts should then be directed to formulate and implement policy of auditable quality management systems, such as Hazard Analysis Critical Control Point (HACCP), to minimise identified health risks to the consumer.