Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New bacteria discovered in raw milk

17.11.2008
Raw milk is illegal in many countries as it can be contaminated with potentially harmful microbes. Contamination can also spoil the milk, making it taste bitter and turn thick and sticky.

Now scientists have discovered new species of bacteria that can grow at low temperatures, spoiling raw milk even when it is refrigerated. According to research published in the November issue of the International Journal of Systematic and Evolutionary Microbiology, the microbial population of raw milk is much more complex than previously thought.

"When we looked at the bacteria living in raw milk, we found that many of them had not been identified before," said Dr Malka Halpern from the University of Haifa, Israel. "We have now identified and described one of these bacteria, Chryseobacterium oranimense, which can grow at cold temperatures and secretes enzymes that have the potential to spoil milk."

New technologies are being developed to reduce the initial bacterial counts of pasteurized milk to very low levels. Most enzymes will be denatured at the high temperatures used during pasteurisation, which means they will stop working. However, the heat-stable enzymes made by cold-tolerant bacteria will still affect the flavour quality of fluid milk and its products. Because of this, research into cold-tolerant bacteria and the spoilage enzymes they produce is vital.

"Milk can be contaminated with many different bacteria from the teat of the cow, the udder, milking equipment and the milking environment," said Dr Halpern. "Milk is refrigerated after collection to limit the growth of microbes. During refrigeration, cold-tolerant, or psychrotolerant, bacteria that can grow at 7°C dominate the milk flora and play a leading role in milk spoilage. Although we have not yet determined the impact on milk quality of C. oranimense and two other novel species (C. haifense and C. bovis) that were also identified from raw milk samples, the discovery will contribute to our understanding the physiology of these organisms and of the complex environmental processes in which they are involved. There is still a lot to learn about the psychrotolerant bacterial flora of raw milk."

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 72°C 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 important that we develop sensitive and efficient tools to monitor the presence of these cold-tolerant bacteria."

Lucy Goodchild | alfa
Further information:
http://www.sgm.ac.uk

More articles from Life Sciences:

nachricht Nanoparticle Exposure Can Awaken Dormant Viruses in the Lungs
16.01.2017 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt

nachricht Cholera bacteria infect more effectively with a simple twist of shape
13.01.2017 | Princeton University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

Im Focus: Bacterial Pac Man molecule snaps at sugar

Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.

The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...

Im Focus: Newly proposed reference datasets improve weather satellite data quality

UMD, NOAA collaboration demonstrates suitability of in-orbit datasets for weather satellite calibration

"Traffic and weather, together on the hour!" blasts your local radio station, while your smartphone knows the weather halfway across the world. A network of...

Im Focus: Repairing defects in fiber-reinforced plastics more efficiently

Fiber-reinforced plastics (FRP) are frequently used in the aeronautic and automobile industry. However, the repair of workpieces made of these composite materials is often less profitable than exchanging the part. In order to increase the lifetime of FRP parts and to make them more eco-efficient, the Laser Zentrum Hannover e.V. (LZH) and the Apodius GmbH want to combine a new measuring device for fiber layer orientation with an innovative laser-based repair process.

Defects in FRP pieces may be production or operation-related. Whether or not repair is cost-effective depends on the geometry of the defective area, the tools...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

Multiregional brain on a chip

16.01.2017 | Power and Electrical Engineering

New technology enables 5-D imaging in live animals, humans

16.01.2017 | Information Technology

Researchers develop environmentally friendly soy air filter

16.01.2017 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>