Milk Quality & Safety: Cooling and Pasteurization are Critical

February 20, 2014 12:40 AM

By: Alvaro Garcia, Professor & Dairy Specialist, SDSU Extension

Milk is rarely in the news as a food that causes health concerns. The main reason for this has been the strict sanitary control points from farm to table. Two aspects of milk handling have been critical for this happen: milk cooling, and pasteurization.

Before the 1880s, no farm in the U.S. had access to electricity, and until the 1930s very few were able to incorporate it. It was well-known then that milk had to be kept cool for it to be preserved adequately. Small farmsteads cooled it by placing the container in the cellar, lowering the bucket into the well, or in metal milk storage cans placed in cold water. President Roosevelt established the Rural Electrification Administration in 1935 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. In 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 important, milk cooling alone did not guarantee a safe product. Bacteria in cooled milk are "dormant" waiting for the right conditions to proliferate. 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.

In the 1800’s raw milk was responsible for 25% 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 children to combat infant mortality. In 1903 child mortality was 15% across the US whereas in New York it had already dropped to 7% 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 and nowadays we almost take food safety for granted. 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 the undesired outcome. The risk of foodborne disease has increased between 1993 and 2006. Outbreaks associated with raw milk consumption have more than doubled (5.2 per year) compared to those between 1973 and1992. 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.

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% of patients with sporadic, domestically-acquired gastrointestinal infections had reported raw milk consumption. Children were the ones most affected with 76 percent of those five years of age or less 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% 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 the state. 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.

Seatbelt laws are not written to infringe on U.S. citizens liberties nor have policemen write tickets when we don’t wear them. 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. As of lately fluid milk consumption has been constantly and steadily decreasing among the U.S. population. Raw milk sales and any resulting outbreaks will challenge this reputation and undermine the confidence placed in one of the pillars of a highly nutritious diet.

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