There is an ongoing debate about the benefits and risks of drinking unpasteurised milk. Some people believe the health benefits resulting from the extra nutrient content of raw milk outweigh the risk of ingesting potentially dangerous microbes, such as Mycobacterium bovis, which can cause tuberculosis, and Salmonella species. Because of these risks, many countries have made the sale of unpasteurised milk illegal. Pasteurisation involves heating milk to around 72C for 15-20 seconds in order to reduce the number of microbes in the liquid so they are unlikely to cause disease. Some bacteria produce extracellular enzymes that are remarkably heat tolerant and can resist pasteurisation. Lipase enzymes cause flavour defects and proteases can lead to bitterness and reduced yields of soft cheese.
Raw milk is consumed in rural areas of Europe and is also available in large cities. Distribution of unpasteurised milk is legal in England, Wales and Northern Ireland but illegal in Scotland. There are around 275 establishments in England that are approved by the Food Standards Agency to sell raw milk. However, the green-top bottles must display a warning that indicates the content has not been heat-treated and may contain harmful organisms. Furthermore, farmers are not allowed to sell unpasteurised dairy products if their herd is suspected to be infected with bovine tuberculosis.
"In Israel, dairy companies estimate that cold-tolerant bacteria can cause a 10% loss of milk fats and proteins. When researchers looked at these bacterial communities, they found that 20% of the bacteria isolated were found to be novel species and 5% of these were members of the genus Chryseobacterium," said Dr Halpern. "Because of their effect on milk quality, it is
|Contact: Lucy Goodchild|
Society for General Microbiology