Milk Hygiene

After mentioning Camplyobacter the other day, I thought it would be worthwhile to discuss milk, a somewhat controversial and often passionate subject matter.  FYI when I say milk I’m referring to milk that comes from cows, goats, and sheep.  I think the best place to start this exciting series is with milk pasteurization, which many consider to be one of public health’s most effective food safety interventions. 

What is milk pasteurization?  

It is the process of heating milk or a milk product to a specified temperature and for a certain about of time.  It's objectives are to destroy any pathogenic microorganisms that might be present in milk such as Brucella, Mycobacterium species, Coxiella burnetii, Listeria, Campylobacter and to enhance the shelf life of milk/milk products.  It was developed in the 1860s by Louis Pasteur.  In the United States routine pasteurization of milk began in the 1920s and became widespread by 1950.  It has led to dramatic decreases in the amount of people getting sick from diseases transmitted by milk.

Pasteurization is not sterilization.  In other words, milk spoilage is delayed not prevented.

Current time-temperature recommendations are based on the death time of Coxiella burnetii the causative agent of Q Fever, which is 145 F.

Methods of Pasteurization:

• High Temperature Short Time treatment milk is pasteurized at 161 F for 15 seconds.
• Ultrapasteurized is when milk has been pasteurized at or above 280 F for at least 2 seconds, either before or after packaging.  Purpose is to produce an extended shelf life. 
• Low Temperature Long Time treatment milk is pasteurized at 145 F for 30 minutes.

How does milk become contaminated?  

• Milk from a healthy cow has very few bacteria but milk from a cow with an infected udder (mastitis) has an extremely high bacterial count.
• Dirt, hair, feces from the exterior of the animal
• If the udder is not properly cleaned and sanitized before milking dirt, hair, and feces can contaminate milk.
• Bacteria from the animals' coat can potentially contaminate milk.  
• Environmental contamination from feces, dirt, grain dust, etc.   
• Milk equipment
• Humans can pass dirt to the cow and milk
• Rodents

Does Pasteurization lessen the nutritional content of milk?

No. There have been many studies that have proven that pasteurization does not significantly change the nutritional value of milk or milk products.