by Whitney Flach
A study conducted by Purdue University has found that the rapid heating and cooling of milk significantly reduces the amount of harmful bacteria present, in fluid dairy milk, and can extend it’s shelf life by several weeks. The study was funded by the Agricultural Research Service of the U.S. Department of Agriculture, the Center for Food Safety Engineering at Purdue University and Millisecond Technologies.
Developed by Louis Pasteur in the 19th century, pasteurization, which removes significant amounts of harmful pathogens that can cause illness and eventually spoil dairy products, is considered a high-temperature, short-time method. The treatment gives milk a shelf life of about 2-3 weeks.
When the scientist used the low-temperature, short-time (LTST) method they sprayed tiny droplets of pasteurized milk, inoculated with Lactobacillus and Pseudomonas bacteria, through a heated, pressurized chamber. While in the chamber temperatures were rapidly raised about 10°C but still below the 70°C needed for pasteurization. The treatment extended shelf life to up to 63 days, and lowered bacterial levels.
Purdue associate professor in the Department of Food Science Bruce Applegate, Ph.D. says, “It’s an add-on to pasteurization, but it can add shelf life of up to five, six or seven weeks to cold milk.” He continues on saying, “With the treatment, you’re taking out almost everything. Whatever does survive is at such a low level that it takes much longer for it to multiply to a point at which it damages the quality of the milk.”
Sensory tests were ran which compared pasteurized milk with milk that had been pasteurized and run through Millisecond Technologies, a New-York-based company process. Panelists did not detect differences in aroma, taste, color, or aftertaste between the products.
An assistant professor of animal science at the University of Tennessee, Phillip Myer said the technology could reduce waste, and allow milk to reach distant locations where transport times using only pasteurization would mean that milk would have a short shelf life upon arrival. Applegate said, the process could be tested without pasteurization to determine if it could stand alone as a treatment for eliminating harmful bacteria from milk.