Cooling and pasteurization are critical aspects of milk quality and safety, and because of strict sanitary control points from farm to table milk is rarely in the news as a food that causes health concerns, explained Alvaro Garcia, SDSU Extension Dairy Specialist.
"Two aspects of milk handling which have been critical for food safety are milk cooling and pasteurization," he said.
Garcia shared some history to further explain the point.
"Before the 1880s, no farm in the U.S. had access to electricity, and until the 1930s very few were able to incorporate it," Garcia said.
He added that it was well-known that milk had to be kept cool for it to be preserved adequately; but without refrigeration, many small farmsteads cooled milk by placing the container in the cellar, lowering the milk bucket into the well or storing it in metal milk storage cans placed in cold water.
Then in 1935, President Roosevelt established the Rural Electrification Administration to help farmers meet the growing demand for electricity.
"Rural electrification and increased availability of motor vehicles after the First World War encouraged bulk transport of milk to minimize inefficient handling," Garcia said.
He added that by the 1950's, bulk storage tanks began replacing milk cans for on-farm storage and allowed farmers to cool their milk while awaiting pickup by a larger milk truck.
While cooling is important, Garcia quickly pointed out, alone it does not guarantee a safe product.
"Bacteria in cooled milk are "dormant" and waiting for the right conditions to proliferate," he said. "They need warm temperatures and food to "wake up" and grow, both of which they find in warm milk and inside the human body. Healthy humans can fight them off to a certain extent; on the other hand not so much children, the elderly and those with compromised immunity."
A little more history
In the 1800's raw milk was responsible for 25 percent of all foodborne outbreaks in the U.S. In 1892, German immigrant's Nathan Straus and his wife Sara privately funded the Pasteurized Milk Laboratory in New York to offer safe pasteurized milk to combat infant mortality. In 1903 child mortality was 15 percent across the U.S. whereas in New York it had already dropped to 7 percent by early 1900.
Straus was the leading proponent of pasteurization which at the time helped eliminate hundreds of thousands of deaths per year due to milk-borne illnesses.
"Generations have passed since milk was responsible for the majority of foodborne illnesses. We have lost the collective memory of what it meant to our grandparents," Garcia said. "Nowadays we almost take milk safety for granted."
Raw milk accounts for an increase in current milkborne illnesses
Between 1973 and 1992 the number of raw milk-originated outbreaks was 2.4 per year. Over the last 20 years, the consumption of raw milk products has increased, and with it, Garcia said, the undesired outcome.
"The risk of milkborne disease has increased between 1993 and 2006," he said. "Outbreaks associated with raw milk consumption have more than doubled (5.2 per year) compared to those between 1973 and1992."
Garcia said that research from the Centers for Disease Control (CDC) shows the rate of raw milk outbreaks and products made from it was 150 times greater than those linked to pasteurized milk.
And, Garcia said outbreaks of foodborne diseases originating from raw milk reported by the CDC seem to be just the tip of the iceberg.
"Analytical data from one decade (2001-2010) of surveillance revealed that 3.7 percent of patients with sporadic, domestically-acquired gastrointestinal infections had reported raw milk consumption," Garcia said.
Children were the ones most affected, with 76 percent of those 5 years of age or younger having been served raw milk from their farm or that of a relative's. Severe illness was observed, including Hemolytic uremic syndrome (rupturing of red blood cells) among 21 percent of Escherichia coli 0157-infected children, with one death reported.
"The number of individuals with sporadic laboratory-confirmed infections associated with raw milk consumption was 25 times greater than outbreaks reported by the CDC in Minnesota," Garcia said.
Based on these results, the report concludes that 17 percent of raw-milk consumers in Minnesota had become ill with gastrointestinal pathogenic bacteria.
"It becomes clear from this study that outbreaks reported by the CDC are only a fraction of illnesses associated with raw milk consumption," he said.
Milk pasteurization is for your safety
Garcia compares pasteurization of milk to other every-day safety precautions.
"Seatbelt laws are not written to infringe on U.S. citizens' liberties, nor for policemen to write tickets when we don't wear them," Garcia said. "Milk pasteurization is also in place to protect the public from potentially life-threatening health issues. This well-proven and safe food processing technique has helped create a partnership of trust among producers, industry, and consumers."
"Illness and disease resulting from raw milk consumption will challenge this reputation and undermine the confidence placed in one of the pillars of a highly nutritious diet," he said.