Improved Food Quality Through the Study of Raw Milk

A new study conducted by researchers at the University of California, Davis, may be the key in helping food companies improve the quality of their dairy products.

In the study, published in the journal mBio on August 23, the researchers revealed that fresh or raw milk transported from farms to dairy processing facilities in tanker trucks contains a diverse mix of microbes, which varies from season to season.

“The majority of the milk produced in California have a core group of bacteria that is really unique to milk, and it didn’t matter where we looked geographically,” says the study’s lead author, Maria L Marco, PhD, associate professor for the Department of Food Science & Technology at the University of California, Davis. “Once the milk enters into the processing facility, there is some legacy of that raw milk from the tanker going into the storage holding units but the bacterial quality of milk will change once put into the processing facility itself.”

For the study, the researchers sampled and analyzed raw cow’s milk using gene sequencing from 899 tanker trucks as they arrived at two dairy processors in the state’s San Joaquin Valley during the spring, summer, and fall seasons.

The results revealed that a broad mix of bacteria was present, which could be the result of anything from raw milk’s high nutrient content, to the numerous potential sources of bacteria associated with dairies, such as the cows’ skin, feed, bedding, and aerosols, or the human handlers and the equipment and containers used to collect, store, and transport the raw milk.

“We’re taking a comprehensive view of microbes and final products in a way that’s never been possible until now. We found that a little over half of the bacterial groups identified represented less than 1 percent of the total microbial content,” Dr. Marco says. “What we’re trying to do is to be able to provide this modern technique in a way that food processing companies can use it in-house in a rapid way to make informed decisions on the product and the potential for incoming ingredients to cause a problem in the end.”

Furthermore, the paper shows that the bacterial composition of raw milk stored in silos at processing plants was somewhat distinct from that of the tanker trucks, with one group of silos containing microbial populations similar in makeup to the milk from the tanker trucks, while another having distinctly different microbial populations dominated by Acinetobacter and Lactococcus bacteria.

The study’s results, Dr. Marco believes, will help aid in the efforts of increased food safety for the dairy industry going forward as identification of these raw-milk microbes and their abundance will help dairy processors develop new and effective sanitation procedures and process controls. She and her team are also now applying the technique to cheese and other dairy products.

“What our research has done is set an approach to identify bacteria that are more or less likely causing these problems in the end. Our early-on stage of interrogating milk at different processing points, help identify the hot areas we need to focus in on,” says Dr. Marco. “We have a lot of questions right now on what bacteria are in our foods and our environment, and I think we took a step forward to know what kind of questions to ask and refine them and hopefully solve problems in quality issues for dairy products.”