5 Fortifying Facts About Dairy Milk and Microbes

It’s almost summer, and to me that means two things: heat and ice cream. I’m honoring National Dairy Month by exploring how the frozen confection that is sugar and cow’s milk, and other food like it, works its sweet biochemical magic.

I always order my ice cream in cones — and I never contemplate what happens to the milk and its chemical constituents along the way before and after each lick. A lot happens, especially in microbial activity. Here are five fortifying facts about dairy products and microbes that are new to me and put One Health, with its links between animal, human and environmental health, on the tip of my tongue.

Micro Lesson in Microbiology

First things first: microbes are tiny microorganisms, like bacteria and fungi, that process organic material. Knowing more about microbes tells us about fermentation (and much more) in our foods. For dairy, knowing more about microbes will help improve sanitation and handling of milk products. Food science experts work to identify properties that boost quality of milk, an important step toward reducing malnutrition in the United States and worldwide.

Close up view of milk samples in tubes for analysis in a microbiology lab - One Health UC Davis
Samples of bovine milk are ready for analysis in the Daniela Barile Food Science Laboratory at UC Davis. (Gregory Urquiaga/UC Davis)

1. Microbes wear multiple hats.

Not all bacteria and their associated enzymes are wiped out during the pasteurization process. The remaining bacteria are still able to cause spoilage and quality defects in dairy foods. Yet dairy carbohydrates support the growth of probiotics, and dairy foods can buffer probiotics from exposure to acidic conditions in our stomachs. 

2. Microbes tag along from many sources in the dairy production path.

The cows’ skin, bedding and aerosols; human handlers; and the equipment and containers used to collect, store and transport milk are all likely bacterial sources. 

3. Silos score one on tanker trucks for the microbial makeup of raw milk.

Environmental conditions matter for dairy microbes. The bacterial composition of raw milk stored in silos at processing plants differed from the composition inside tanker trucks used to transport milk in a recent study led by Maria Marco, a UC Davis associate professor of food science and technology. In the study, one group of silos contained microbial populations similar in makeup to the milk from tanker trucks, while another group of silos had distinct microbial populations dominated by Acinetobacter and Lactococcus bacteria. Researchers sampled raw cow’s milk from 899 tanker trucks as they arrived at two dairy processors in California’s San Joaquin Valley. They used gene sequencing to analyze the samples. 

4. Dairy products and probiotics are a match made in the refrigerator.

We benefit from using technology to help manage microbial activity. Cold temperature incubation contributed to higher levels of a probiotic protein in dairy foods in another study by Maria Marco of UC Davis. Marco's team of researchers wanted to know how the storage of dairy products affected the presence of probiotics in our intestines. They found that 205 Lactobaccilus casei proteins were produced in mice either at higher levels or exclusively when the probiotic was allowed to incubate in refrigerated milk. These proteins, which were produced before the dairy was even consumed, were key to the survival of the probiotic in the digestive tract of the mice. 

5. Microbes and the gut join forces for brain development.

It’s hard to resist using “food for thought” to describe research about the microbiota-gut-brain axis. But the emerging findings are anything but cliché: Research has revealed that bacterial colonization of the intestine plays an important and direct role in neurological functioning — and in our understanding of psychiatric disorders from anxiety to autism. 

Close up of a cow trying to lick the camera
A dairy cow at UC Davis wants a lick before it's too late! (Gregory Urquiaga/UC Davis)


But brain freeze from eating ice cream too quickly, that’s a different thing entirely. I should be so wise as to slowly savor my summer treat and digest more thoroughly its creamy goodness and complex role in health.

Amy Whitcomb is an editor on the web team in Strategic Communications.

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