Food safety of raw milk

Raw or unpasteurised milk

is milk that comes directly from a cow’s, goat’s, sheep or other animal’s udder, and has not been treated to kill bacteria.

Is unpasteurised milk safe to drink?

Consuming raw milk can cause severe illness due to the possible presence of harmful bacteria such as Salmonella, E. coli O157, Campylobacter and Listeria monocytogenes. Pregnant women, young children (particularly babies), the elderly, and people with weakened immune systems are at greatest risk of getting sick and the consequences for them can be more severe.

How does milk get contaminated?

Pathogenic bacteria can pass into milk directly from an infected udder or milk can get contaminated from the dairy farm environment during milking e.g. from unseen faecal contamination of the teat.

How can I tell if raw milk is contaminated?

There is no way of telling by taste, sight or smell that raw milk contains harmful bacteria.

Have serious outbreaks of foodborne disease been caused by raw milk consumption?

Globally, outbreaks of illness caused by raw milk consumption occur regularly. Recorded outbreaks include cases of death, stillbirth and miscarriages. According to the US Centers for Disease Control and Prevention, raw milk is responsible for nearly three times more hospitalisations than any other foodborne source.

In New Zealand a disease outbreak associated with raw milk consumption occurred in May/June 2011 and involved eight people. In 2009, an outbreak of campylobacteriosis in Northland due to raw milk affected 16 people.

Have bacteria associated with severe foodborne disease been found in raw milk in New Zealand?

An on-going MPI survey has sporadically identified in New Zealand raw milk the presence of harmful bacteria such as Listeria monocytogenes, Shiga-toxin producing Escherichia coli and Campylobacter.

Can we eliminate harmful bacteria in raw milk from our dairy farms?

Most harmful bacteria are present as a normal flora of the gut of ruminants and are ubiquitous in the environment. No matter how carefully the cows are milked there is always a possibility of these bacteria being present in raw milk.

Pasteurisation is the only reliable method to kill pathogens in the milk.

Does pasteurisation significantly reduce health benefits of milk?

Pasteurisation has minimal effect on milk fat and protein composition. It does not affect mineral stability, milk mineral content, or mineral bioavailability.

Vitamins present in milk in high levels (riboflavin, B6 and B12) are reasonably heat stable. Folate utilisation is not reduced in pasteurised milk. There is 10% loss of vitamin C due to pasteurisation, but milk is not a significant dietary source of the vitamin.

While it is true that the heating process can inactivate some enzymes important for human health in milk, the pasteurisation process adopted in New Zealand (72oC for 15 sec) has minimal effect on enzymatic activity.

What can I do to minimise the risk of getting ill from raw milk?

If you decide to consume raw milk make sure that you are getting milk sourced from trusted farmers. Although adherence to good hygienic practices during milking and storage cannot guarantee microbial safety of raw milk, it reduces the risk of bacterial contamination. Keep raw milk under refrigeration (4°C or less) and discard if it has spent more than two hours at room temperature.

The young, elderly, pregnant and immuno-compromised (i.e. those whose immune system is weakened) should avoid consumption of raw milk completely as they are at greatest risk from infection.